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BEGIN:VEVENT
SUMMARY:Tiago Jardim Da Fonseca (Oxford)
DTSTART:20200422T150000Z
DTEND:20200422T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/1
DESCRIPTION:Title: On
Fourier coefficients of Poincaré series\nby Tiago Jardim Da Fonseca (
Oxford) as part of London number theory seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LNTS/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ila Varma (Toronto)
DTSTART:20200429T150000Z
DTEND:20200429T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/2
DESCRIPTION:Title: Mal
le's conjecture for octic D4-fields\nby Ila Varma (Toronto) as part of
London number theory seminar\n\n\nAbstract\nWe consider the family of nor
mal octic fields with Galois group $D_4$\, ordered by their discriminants.
In forthcoming joint work with Arul Shankar\, we verify the strong form o
f Malle's conjecture for this family of number fields\, obtaining the orde
r of growth as well as the constant of proportionality. In this talk\, we
will discuss and review the combination of techniques from analytic number
theory and geometry-of-numbers methods used to prove this and related res
ults.\n
LOCATION:https://researchseminars.org/talk/LNTS/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chris Lazda (Warwick)
DTSTART:20200506T150000Z
DTEND:20200506T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/3
DESCRIPTION:Title: A N
éron-Ogg-Shafarevich criterion for K3 surfaces\nby Chris Lazda (Warwi
ck) as part of London number theory seminar\n\n\nAbstract\nThe naive analo
gue of the Néron–Ogg–Shafarevich criterion fails for K3 surfaces\, th
at is\, there exist K3 surfaces over Henselian\, discretely valued fields
K\, with unramified etale cohomology groups\, but which do not admit good
reduction over K. Assuming potential semi-stable reduction\, I will show h
ow to correct this by proving that a K3 surface has good reduction if and
only if its second cohomology is unramified\, and the associated Galois re
presentation over the residue field coincides with the second cohomology o
f a certain “canonical reduction” of X. This is joint work with B. Chi
arellotto and C. Liedtke.\n
LOCATION:https://researchseminars.org/talk/LNTS/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chantal David (Concordia)
DTSTART:20200513T150000Z
DTEND:20200513T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/4
DESCRIPTION:Title: Non
-vanishing cubic Dirichlet L-functions at s = 1/2\nby Chantal David (C
oncordia) as part of London number theory seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LNTS/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rong Zhou (Imperial)
DTSTART:20200520T150000Z
DTEND:20200520T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/5
DESCRIPTION:Title: Ind
ependence of $l$ for Frobenius conjugacy classes attached to abelian varie
ties\nby Rong Zhou (Imperial) as part of London number theory seminar\
n\n\nAbstract\nLet $A$ be an abelian variety over a number field $E\\subse
t \\mathbb{C}$ and let $v$ be a place of good reduction lying over a prime
$p$. For a prime $l\\neq p$\, a theorem of Deligne implies that upon maki
ng a finite extension of $E$\, the Galois representation on the $l$-adic T
ate module factors as $\\rho_l:\\Gamma_E\\rightarrow G_A(\\mathbb{Q}_l)$\,
where $G_A$ is the Mumford-Tate group of $A$. We prove that the conjugacy
class of $\\rho_l(Frob_v)$ is defined over $\\mathbb{Q}$ and independent
of $l$. This is joint work with Mark Kisin.\n
LOCATION:https://researchseminars.org/talk/LNTS/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matteo Tamiozzo (Imperial)
DTSTART:20200527T150000Z
DTEND:20200527T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/6
DESCRIPTION:Title: Blo
ch-Kato special value formulas for Hilbert modular forms\nby Matteo Ta
miozzo (Imperial) as part of London number theory seminar\n\n\nAbstract\nT
he Bloch-Kato conjectures predict a relation between arithmetic invariants
of a motive and special values of the associated $L$-function. We will ou
tline a proof of (the $p$-part of) one inequality in the relevant special
value formula for Hilbert modular forms of parallel weight two\, in analyt
ic rank at most one.\n
LOCATION:https://researchseminars.org/talk/LNTS/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yunqing Tang (Paris-Saclay)
DTSTART:20200603T150000Z
DTEND:20200603T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/7
DESCRIPTION:Title: Pic
ard ranks of reductions of K3 surfaces over global fields\nby Yunqing
Tang (Paris-Saclay) as part of London number theory seminar\n\n\nAbstract\
nFor a K3 surface $X$ over a number field with potentially good reduction
everywhere\, we prove that there are infinitely many primes modulo which t
he reduction of $X$ has larger geometric Picard rank than that of the gene
ric fiber $X$. A similar statement still holds true for ordinary K3 surfac
es with potentially good reduction everywhere over global function fields.
In this talk\, I will present the proofs via the (arithmetic) intersectio
n theory on good integral models (and its special fibers) of $\\mathrm{GSp
in}$ Shimura varieties. These results are generalizations of the work of C
harles on exceptional isogenies between reductions of a pair of elliptic c
urves. This talk is based on joint work with Ananth Shankar\, Arul Shankar
\, and Salim Tayou and with Davesh Maulik and Ananth Shankar.\n
LOCATION:https://researchseminars.org/talk/LNTS/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vesselin Dimitrov (Toronto)
DTSTART:20200612T150000Z
DTEND:20200612T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/8
DESCRIPTION:Title: p-a
dic Eisenstein series\, arithmetic holonomicity criteria\, and irrationali
ty of the 2-adic $\\zeta(5)$\nby Vesselin Dimitrov (Toronto) as part o
f London number theory seminar\n\n\nAbstract\nIn this exposition of a join
t work in progress with Frank Calegari and Yunqing Tang\, I will explain a
new arithmetic criterion for a formal function to be holonomic\, and how
it revives an approach to the arithmetic nature of special values of L-fun
ctions. The new consequence to be proved in this talk is the irrationality
of the 2-adic version of $\\zeta(5)$ (of Kubota-Leopoldt). But I will als
o draw a parallel to a work of Zudilin\, and try to leave some additional
open ends where the holonomicity theorem could be useful. The ingredients
of the irrationality proof are Calegari's p-adic counterpart of the Apery-
Beukers method\, which is based on the theory of overconvergent p-adic mod
ular forms (IMRN\, 2005) taking its key input from Buzzard's theorem on p-
adic analytic continuation (JAMS\, 2002)\, and a Diophantine approximation
method of Andre enhanced to a power of the modular curve $X_0(2)$. The ov
erall argument\, as we shall discuss\, turns out to bear a surprising affi
nity to a recent solution of the Schinzel-Zassenhaus conjecture on the orb
its of Galois around the unit circle.\n
LOCATION:https://researchseminars.org/talk/LNTS/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yifeng Liu (Yale)
DTSTART:20200617T130000Z
DTEND:20200617T140000Z
DTSTAMP:20260315T025337Z
UID:LNTS/9
DESCRIPTION:Title: Bei
linson-Bloch conjecture and arithmetic inner product formula\nby Yifen
g Liu (Yale) as part of London number theory seminar\n\n\nAbstract\nIn thi
s talk\, we study the Chow group of the motive associated to a tempered gl
obal $L$-packet $\\pi$ of unitary groups of even rank with respect to a CM
extension\, whose global root number is $-1$. We show that\, under some r
estrictions on the ramification of $\\pi$\, if the central derivative $L'(
1/2\,\\pi)$ is nonvanishing\, then the $\\pi$-nearly isotypic localization
of the Chow group of a certain unitary Shimura variety over its reflex fi
eld does not vanish. This proves part of the Beilinson--Bloch conjecture f
or Chow groups and L-functions (which generalizes the B-SD conjecture). Mo
reover\, assuming the modularity of Kudla's generating functions of specia
l cycles\, we explicitly construct elements in a certain $\\pi$-nearly iso
typic subspace of the Chow group by arithmetic theta lifting\, and compute
their heights in terms of the central derivative $L'(1/2\,\\pi)$ and loca
l doubling zeta integrals. This confirms the conjectural arithmetic inner
product formula proposed by me a decade ago. This is a joint work with Cha
o Li.\n
LOCATION:https://researchseminars.org/talk/LNTS/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jared Weinstein (Boston University)
DTSTART:20200708T150000Z
DTEND:20200708T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/12
DESCRIPTION:Title: Pa
rtial Frobenius structures\, Tate’s conjecture\, and BSD over function f
ields.\nby Jared Weinstein (Boston University) as part of London numbe
r theory seminar\n\n\nAbstract\nTate’s conjecture predicts that Galois-i
nvariant classes in the $l$-adic cohomology of a variety are explained by
algebraic cycles. It is known to imply the conjecture of Birch and Swinne
rton-Dyer (BSD) for elliptic curves over function fields. When the variet
y\, now assumed to be in characteristic p\, admits a “partial Frobenius
structure”\, there is a natural extension of Tate’s conjecture. Ass
uming this conjecture\, we get not only BSD\, but the following result: t
he top exterior power of the Mordell-Weil group of an elliptic curve is sp
anned by a “Drinfeld-Heegner” point. This is a report on work in prog
ress.\n
LOCATION:https://researchseminars.org/talk/LNTS/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rachel Newton
DTSTART:20201007T150000Z
DTEND:20201007T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/13
DESCRIPTION:Title: Ev
aluating the wild Brauer group\nby Rachel Newton as part of London num
ber theory seminar\n\n\nAbstract\nThe local-global approach to the study o
f rational points on varieties over number fields begins by embedding the
set of rational points on a variety X into the set of its adelic points. T
he Brauer-Manin pairing cuts out a subset of the adelic points\, called th
e Brauer-Manin set\, that contains the rational points. If the set of adel
ic points is non-empty but the Brauer-Manin set is empty then we say there
's a Brauer-Manin obstruction to the existence of rational points on X. Co
mputing the Brauer-Manin pairing involves evaluating elements of the Braue
r group of X at local points. If an element of the Brauer group has order
coprime to p\, then its evaluation at a p-adic point factors via reduction
of the point modulo p. For p-torsion elements this is no longer the case:
in order to compute the evaluation map one must know the point to a highe
r p-adic precision. Classifying p-torsion Brauer group elements according
to the precision required to evaluate them at p-adic points gives a filtra
tion which we describe using work of Bloch and Kato. Applications of our w
ork include addressing Swinnerton-Dyer's question about which places can p
lay a role in the Brauer-Manin obstruction. This is joint work with Martin
Bright.\n
LOCATION:https://researchseminars.org/talk/LNTS/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ziyang Gao
DTSTART:20201014T150000Z
DTEND:20201014T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/14
DESCRIPTION:Title: Bo
unding the number of rational points on curves\nby Ziyang Gao as part
of London number theory seminar\n\n\nAbstract\nMazur conjectured\, after F
altings’s proof of the Mordell conjecture\, that the number of rational
points on a curve of genus g at least 2 defined over a number field of deg
ree d is bounded in terms of g\, d and the Mordell-Weil rank. In particula
r the height of the curve is not involved. In this talk I will explain how
to prove this conjecture and some generalizations. I will focus on how fu
nctional transcendence and unlikely intersections are applied in the proof
. If time permits\, I will talk about how the dependence on d can be furth
ermore removed if we moreover assume the relative Bogomolov conjecture. Th
is is joint work with Vesselin Dimitrov and Philipp Habegger.\n
LOCATION:https://researchseminars.org/talk/LNTS/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rob Kurinczuk (Imperial College London)
DTSTART:20201028T160000Z
DTEND:20201028T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/15
DESCRIPTION:Title: Mo
duli of Langlands parameters and LLIF\nby Rob Kurinczuk (Imperial Coll
ege London) as part of London number theory seminar\n\n\nAbstract\nThe con
jectural local Langlands correspondence connects representations of p-adic
groups to certain representations of Galois groups of local fields called
Langlands parameters. In recent joint work with Dat\, Helm\, and Moss\,
we have constructed moduli spaces of Langlands parameters over Z[1/p] and
studied their geometry. We expect this geometry is reflected in the repre
sentation theory of the p-adic group. In particular\, our main conjecture
"local Langlands in families" describes the GIT quotient of the moduli sp
ace of Langlands parameters in terms of the centre of the category of repr
esentations of the p-adic group generalising a theorem of Helm-Moss for GL
(n).\n
LOCATION:https://researchseminars.org/talk/LNTS/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:João Lourenço
DTSTART:20201111T160000Z
DTEND:20201111T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/16
DESCRIPTION:Title: Th
e Scholze-Weinstein conjecture on local models\nby João Lourenço as
part of London number theory seminar\n\n\nAbstract\nInspired by the theory
of local models of Shimura varieties\, Scholze-Weinstein proposed a conje
cture predicting representability of certain minuscule closed sub-v-sheave
s of their p-adic de Rham affine Grassmannian by a projective flat and geo
metrically reduced normal scheme.\n\nIn my talk\, I'll explain the motivat
ion behind the problem stemming from Shimura varieties\, review the necess
ary technical background and ultimately sketch a proof for pseudo-tame gro
ups without exceptional factors. To achieve this\, I'll determine the Pica
rd group of the Witt vectors affine Grassmannian as conjectured by Bhatt-S
cholze. Time permitting\, I might outline a (very much incomplete) strateg
y for handling exceptional groups.\n
LOCATION:https://researchseminars.org/talk/LNTS/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Annette Huber (Universität Freiburg)
DTSTART:20201118T160000Z
DTEND:20201118T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/17
DESCRIPTION:Title: Ex
ponential periods and o-minimality\nby Annette Huber (Universität Fre
iburg) as part of London number theory seminar\n\n\nAbstract\n(joint work
with Johan Commelin and Philipp Habegger)\nRoughly\, period numbers are de
fined by integrals of the form\n$\\int_\\sigma\\omega$ with $\\omega$ and
$\\sigma$ of algebraic nature.\nThis can be made precise in very different
languages: as values of\nthe period pairing between de Rham cohomology an
d singular homology\nof algebraic varieties or motives defined over number
fields\, or more\nnaively as\nvolumes of semi-algebraic sets.\n\nMore rec
ently\, exponential periods have come into focus. Roughly\, they\nare of t
he form $\\int_\\sigma e^{-f}\\omega$ with $\\sigma\,\\omega$ and now\nals
o $f$ of algebraic nature. They appear are periods for the Rham complex\no
f an irregular connection. We want to explain how the "naiv" side of\nthe
story can be formulated in this case.\n
LOCATION:https://researchseminars.org/talk/LNTS/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luis Garcia (UCl)
DTSTART:20201209T160000Z
DTEND:20201209T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/20
DESCRIPTION:Title: Ei
senstein classes and hyperplane complements\nby Luis Garcia (UCl) as p
art of London number theory seminar\n\n\nAbstract\nIn recent years several
authors (Sczech\, Nori\, Hill\, Charollois-Dasgupta-Greenberg\, Beilinson
-Kings-Levin) have defined and studied certain group cocycles ("Eisenstein
cocycles") in the cohomology of arithmetic groups. I will discuss how the
se constructions can be understood in terms of equivariant cohomology and
characteristic classes. This point of view relates the cocycles to the the
ta correspondence and leads to generalisations relating the homology of ar
ithmetic groups to algebraic objects such as meromorphic differentials on
hyperplane complements. I will discuss these generalisations and an applic
ation to critical values of L-functions. \n\nThe talk is based on joint wo
rk-in-progress with Nicolas Bergeron\, Pierre Charollois and Akshay Venkat
esh.\n
LOCATION:https://researchseminars.org/talk/LNTS/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pedro Lemos (University College London)
DTSTART:20201216T160000Z
DTEND:20201216T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/21
DESCRIPTION:Title: Re
sidual Galois representations of elliptic curves with image in the normali
ser of a non-split Cartan\nby Pedro Lemos (University College London)
as part of London number theory seminar\n\n\nAbstract\nIt is known that if
$p$ is a prime $>37$\, then the image of the residual Galois representati
on $\\bar{\\rho}_{E\,p}: G_{\\mathbb{Q}}\\rightarrow {\\rm GL}_2(\\mathbb{
F}_p)$ attached to an elliptic curve $E/\\mathbb{Q}$ without complex multi
plication is either ${\\rm GL}_2(\\mathbb{F}_p)$\, or is contained in the
normaliser of a non-split Cartan subgroup of ${\\rm GL}_2(\\mathbb{F}_p)$.
I will report on a recent joint work with Samuel Le Fourn where we improv
e this result by showing that if $p>1.4\\times 10^7$\, then $\\bar{\\rho}_
{E\,p}$ is either surjective\, or its image is the normaliser of a non-spl
it Cartan subgroup of ${\\rm GL}_2(\\mathbb{F}_p)$.\n
LOCATION:https://researchseminars.org/talk/LNTS/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lennart Gehrmann (University of Duisburg-Essen / McGill University
)
DTSTART:20201021T150000Z
DTEND:20201021T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/22
DESCRIPTION:Title: L-
invariants\, completed cohomology and big principal series\nby Lennart
Gehrmann (University of Duisburg-Essen / McGill University) as part of Lo
ndon number theory seminar\n\n\nAbstract\nLet $f$ be a newform of weight $
2$ that is Steinberg at $p$. Darmon showed that the Fontaine-Mazur $L$-inv
ariant of the associated local $p$-adic Galois representation can be compu
ted in terms of the cohomology of $p$-arithmetic subgroups of the group $P
GL_2(\\mathbb{Q})$.\nOn the other hand Breuil showed that one can compute
the $f$-isoyptical part of completed cohomology of the modular curve in te
rms of the cohomology of $p$-arithmetic groups.\nIn this talk I will give
generalizations of both results to higher rank reductive groups. This is p
artly joint work with Giovanni Rosso.\n
LOCATION:https://researchseminars.org/talk/LNTS/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sally Gilles
DTSTART:20201104T160000Z
DTEND:20201104T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/23
DESCRIPTION:Title: Pe
riod morphisms and syntomic cohomology\nby Sally Gilles as part of Lon
don number theory seminar\n\n\nAbstract\nIn 2017\, Colmez and Nizioł prov
ed a comparison theorem between arithmetic p-adic nearby cycles and syntom
ic cohomology sheaves. To prove it\, they gave a local construction using
$(\\varphi\,\\Gamma)$-modules theory which allows to reduce the period iso
morphism to a comparison theorem between Lie algebras. In this talk\, I wi
ll first give the geometric version of this construction before explaining
how to globalize it. This period morphism can be used to describe the é
tale cohomology of rigid analytic spaces. In particular\, we deduce the se
mi-stable conjecture of Fontaine-Jannsen\, which relates the étale cohom
ology of the rigid analytic variety associated to a formal proper semi-sta
ble scheme to its Hyodo-Kato cohomology. This result was also proved by (a
mong others) Tsuji\, via the Fontaine-Messing map\, and by Česnavičius
and Koshikawa\, which generalized the proof of the crystalline conjecture
by Bhatt\, Morrow and Scholze. In the second part of the talk\, I will ex
plain how we can use the previous map to show that the period morphism of
Tsuji and the one of Česnavičius-Koshikawa are the same.\n
LOCATION:https://researchseminars.org/talk/LNTS/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrew Graham (Imperial College London)
DTSTART:20210113T160000Z
DTEND:20210113T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/24
DESCRIPTION:Title: An
ticyclotomic Euler systems for conjugate self-dual representations of $GL(
2n)$\nby Andrew Graham (Imperial College London) as part of London num
ber theory seminar\n\n\nAbstract\nAn Euler system is a collection of Galoi
s cohomology classes which satisfy certain compatibility relations under c
orestriction\, and by constructing an Euler system and relating the classe
s to $L$-values\, one can establish instances of the Bloch--Kato conjectur
e. In this talk\, I will describe a construction of an anticyclotomic Eule
r system for a certain class of conjugate self-dual automorphic representa
tions\, which can be seen as a generalisation of the Heegner point constru
ction. The classes arise from special cycles on unitary Shimura varieties
and are closely related to the branching law associated with the spherical
pair $(GL(n) \\times GL(n)\, GL(2n))$. This is joint work with S.W.A. Sha
h.\n
LOCATION:https://researchseminars.org/talk/LNTS/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Raphael Steiner (ETH Zürich)
DTSTART:20210120T160000Z
DTEND:20210120T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/25
DESCRIPTION:Title: Fo
urth moments and sup-norms with the aid of theta functions\nby Raphael
Steiner (ETH Zürich) as part of London number theory seminar\n\n\nAbstra
ct\nIt is a classical problem in harmonic analysis to bound $L^p$-norms of
eigenfunctions of the Laplacian on (compact) Riemannian manifolds in term
s of the eigenvalue. A general sharp result in that direction was given by
Hörmander and Sogge. However\, in an arithmetic setting\, one ought to d
o better. Indeed\, it is a classical result of Iwaniec and Sarnak that exa
ctly that is true for Hecke-Maass forms on arithmetic hyperbolic surfaces.
They achieved their result by considering an amplified second moment of H
ecke eigenforms. Their technique has since been adapted to numerous other
settings. In my talk\, I shall explain how to use Shimizu's theta function
to express a fourth moment of Hecke eigenforms in geometric terms (second
moment of matrix counts). In joint work with Ilya Khayutin and Paul Nelso
n\, we give sharp bounds for said matrix counts and thus a sharp bound on
the fourth moment in the weight and level aspect. As a consequence\, we im
prove upon the best known bounds for the sup-norm in these aspects. In par
ticular\, we prove a stronger than Weyl-type sub-convexity result.\n
LOCATION:https://researchseminars.org/talk/LNTS/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lynnelle Ye (Stanford University)
DTSTART:20210127T160000Z
DTEND:20210127T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/26
DESCRIPTION:Title: Pr
operness for eigenvarieties\nby Lynnelle Ye (Stanford University) as p
art of London number theory seminar\n\n\nAbstract\nCan a family of finite-
slope modular Hecke eigenforms lying over a punctured disc in weight space
always be extended over the puncture? This was first asked by Coleman and
Mazur in 1998 and settled by Diao and Liu in 2016 using deep\, powerful G
alois-theoretic machinery. We will discuss a new proof which is geometric
and explicit and uses no Galois theory\, and which generalizes in some cas
es to Hilbert modular forms. We adapt an earlier method of Buzzard and Cal
egari based on elementary properties of overconvergent modular forms\, for
which we have to extend the construction of Andreatta-Iovita-Pilloni over
convergent forms farther into the supersingular locus.\n
LOCATION:https://researchseminars.org/talk/LNTS/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lassina Dembélé (University of Luxembourg)
DTSTART:20210203T160000Z
DTEND:20210203T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/27
DESCRIPTION:Title: Fi
nite flat $p$-group schemes over $\\mathbf{Z}$\nby Lassina Dembélé (
University of Luxembourg) as part of London number theory seminar\n\n\nAbs
tract\nConjecture (Abrashkin-Fontaine): For $p$ prime\, the only simple fi
nite flat group schemes of $p$-power order defined over $\\mathbf{Z}$ are
$\\mathbf{Z}/p\\mathbf{Z}$ and $\\mu_p$.\n\nAbrashkin and Fontaine separat
ely proved that this conjecture is true for $p \\le 17$. In this talk\, we
extend their result to the primes $p \\le 37$ under GRH. (This is joint w
ork with René Schoof.)\n
LOCATION:https://researchseminars.org/talk/LNTS/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Juan Esteban Rodriguez Camargo (ENS de Lyon)
DTSTART:20210210T160000Z
DTEND:20210210T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/28
DESCRIPTION:Title: Du
al Eichler-Shimura maps for the modular curve\nby Juan Esteban Rodrigu
ez Camargo (ENS de Lyon) as part of London number theory seminar\n\n\nAbst
ract\nAndreatta-Iovita-Stevens have constructed interpolations of the sm
all slope part of the Eichler-Shimura decomposition for the modular curve.
Roughly speaking\, they defined in a geometric way a map from the overcon
vergent modular symbols of weight k\, to the overconvergent modular forms
of weight k+2. Then\, using classicality theorems of Coleman and Ash-Ste
vens\, they achieved a Hodge-Tate decomposition of the small slope part of
overconvergent modular symbols. On the other hand\, in a recent paper of
Boxer-Pilloni\, the authors proved that higher Coleman and Hida theories
exist for the modular curve. The aim of this talk is to construct geometri
cally a map from the higher cohomology of overconvergent modular forms of
weight -k to the modular symbols as above. We shall recover the Hodge-Tat
e decomposition of the small slope part of modular symbols\, with the addi
tion that all the maps involved are defined using the geometry of the modu
lar curve. If time permits\, we will discuss the compatibility of the prev
ious work with duality.\n
LOCATION:https://researchseminars.org/talk/LNTS/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chao Li (Columbia University)
DTSTART:20210217T160000Z
DTEND:20210217T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/29
DESCRIPTION:Title: Be
ilinson-Bloch conjecture for unitary Shimura varieties\nby Chao Li (Co
lumbia University) as part of London number theory seminar\n\n\nAbstract\n
For certain automorphic representations $\\pi$ on unitary groups\, we show
that if $L(s\, \\pi)$ vanishes to order one at the center $s=1/2$\, then
the associated $\\pi$-localized Chow group of a unitary Shimura variety is
nontrivial. This proves part of the Beilinson-Bloch conjecture for unitar
y Shimura varieties\, which generalizes the BSD conjecture. Assuming Kudla
's modularity conjecture\, we further prove the arithmetic inner product f
ormula for $L'(1/2\, \\pi)$\, which generalizes the Gross-Zagier formula.
We will motivate these conjectures and discuss some aspects of the proof.
We will also mention recent extensions applicable to certain symmetric pow
er L-functions of elliptic curves. This is joint work with Yifeng Liu.\n
LOCATION:https://researchseminars.org/talk/LNTS/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Charlotte Chan (MIT)
DTSTART:20210224T160000Z
DTEND:20210224T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/30
DESCRIPTION:Title: Ge
ometric L-packets of toral supercuspidal representations\nby Charlotte
Chan (MIT) as part of London number theory seminar\n\n\nAbstract\nIn 2001
\, Yu gave an algebraic construction of supercuspidal representations of p
-adic groups (now known to be exhaustive when the residual characteristic
is sufficiently large---Kim\, Fintzen). There has since been a lot of prog
ress towards explicitly constructing the local Langlands correspondence: K
azhdan-Varshavsky and DeBacker-Reeder (depth zero)\, Reeder and DeBacker-S
pice (toral)\, and Kaletha (regular supercuspidals). In this talk\, we pre
sent recent and ongoing work investigating a geometric counterpart to this
story. This is based on joint work with Alexander Ivanov and joint work w
ith Masao Oi.\n
LOCATION:https://researchseminars.org/talk/LNTS/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anders Södergren (Chalmers University of Technology)
DTSTART:20210303T160000Z
DTEND:20210303T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/31
DESCRIPTION:Title: Cu
bic fields\, low-lying zeros and the L-functions Ratios Conjecture\nby
Anders Södergren (Chalmers University of Technology) as part of London n
umber theory seminar\n\n\nAbstract\nIn this talk I will discuss recent wor
k on the low-lying zeros in the family of $L$-functions attached to non-Ga
lois cubic Dedekind zeta functions. In particular\, I will describe the cl
ose relation between these low-lying zeros and precise counting results fo
r cubic fields with local conditions. The main application of this investi
gation is a conditional omega result for cubic field counting functions. I
will also discuss the $L$-functions Ratios Conjecture associated to this
family of Dedekind zeta functions and the fact that the conjecture in its
standard form does not predict all the terms in the family's one-level den
sity of low-lying zeros. This is joint work with Peter Cho\, Daniel Fioril
li and Yoonbok Lee.\n
LOCATION:https://researchseminars.org/talk/LNTS/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Min Lee
DTSTART:20210310T160000Z
DTEND:20210310T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/32
DESCRIPTION:Title: Li
nnik problem for Maass-Hecke cusp forms and effective multiplicity one the
orem\nby Min Lee as part of London number theory seminar\n\n\nAbstract
\nThe strong multiplicity one theorem (for GL(2)\, proved by Jacquet and L
anglands) implies that if two Maass-Hecke cuspforms share the same Laplaci
an eigenvalue and the same Hecke eigenvalues for almost all primes then th
e two forms must be equal up to a constant multiple. In this talk we cons
ider the following question\, an analogue of Linnik’s question for Diric
hlet characters: if the two forms are not equal up to a constant multiple\
, how large can the first prime p be\, such that the corresponding Hecke e
igenvalues differ? Alternatively we can also ask: how large is the dimensi
on of the joint eigenspace of the given finite set of Hecke operators and
the Laplace operator? We approach these two questions with two different m
ethods. This is a joint work with Junehyuk Jung.\n
LOCATION:https://researchseminars.org/talk/LNTS/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emmanuel Lecouturier (Yau Mathematical Sciences Center and Tsinghu
a University (Beijing))
DTSTART:20210317T160000Z
DTEND:20210317T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/33
DESCRIPTION:Title: On
an analogue of a conjecture of Sharifi for imaginary quadratic fields
\nby Emmanuel Lecouturier (Yau Mathematical Sciences Center and Tsinghua U
niversity (Beijing)) as part of London number theory seminar\n\n\nAbstract
\nWe explore a relation between the cohomology of certain Bianchi 3-folds\
, modulo some Eisenstein ideal\, to the arithmetic of imaginary quadratic
fields.\nFor instance\, in the case of Euclidean imaginary quadratic field
s\, we get a relation between modular symbols and cup-products of elliptic
units.\nThis is similar to conjectures of Sharifi for classical modular c
urves\, relating modular symbols to cup-product of cyclotomic units. \nThi
s is work in progress with Jun Wang.\n
LOCATION:https://researchseminars.org/talk/LNTS/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Akshay Venkatesh (Institute for Advanced Study)
DTSTART:20210324T160000Z
DTEND:20210324T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/34
DESCRIPTION:Title: Ce
ntral L-values up to squares\nby Akshay Venkatesh (Institute for Advan
ced Study) as part of London number theory seminar\n\n\nAbstract\nThis is
a report on joint work -- in progress -- with A. Abdurrahman. \nGiven an
everywhere unramified symplectic Galois representation\nover a function fi
eld\, we propose a conjectural formula for its central L-value\nup to squa
res in the coefficient field\, in terms of a certain cohomological invaria
nt\nof the representation. \n \nI'll describe three types of evidence f
or this conjecture\, coming\nfrom numerical examples\, topology\, and auto
morphic forms. \nThen I will discuss (much more speculatively) what the ra
mified/number field\nanalogue of the formula might be\, and its potential
relationship to a theory\nof "higher epsilon factors."\n
LOCATION:https://researchseminars.org/talk/LNTS/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eva Viehmann
DTSTART:20210428T150000Z
DTEND:20210428T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/36
DESCRIPTION:Title: Ne
wton strata on the B$_{dR}$-Grassmannian\nby Eva Viehmann as part of L
ondon number theory seminar\n\n\nAbstract\nRecently\, Fargues and Scholze
laid the foundations for\na geometric Langlands program on the Fargues-Fon
taine curve. One of the\ncentral objects of interest is the stack Bun$_G$
of $G$-bundles on the\ncurve. I will explain how to determine the underlyi
ng topological space\n|Bun$_{G}$| and its relation to the Newton stratific
ation on the\nB$_{dR}$-Grassmannian.\n
LOCATION:https://researchseminars.org/talk/LNTS/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dimitris Koukoulopoulos
DTSTART:20210505T150000Z
DTEND:20210505T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/37
DESCRIPTION:Title: An
atomy of integers\, polynomials and permutations\nby Dimitris Koukoulo
poulos as part of London number theory seminar\n\n\nAbstract\nThere is a f
amous analogy between the statistics of the prime factors of a random inte
ger\, of the irreducible factors of a random polynomial over a finite fiel
d\, and of the cycles of a random permutation. This analogy allows us to t
ransfer techniques and intuition from one setup to the other\, and it has
been in the center of a lot of recent activity in probabilistic number the
ory and group theory. I will survey some of this progress\, focusing in pa
rticular on results about the irreducibility of randomly chosen polynomial
s with 0\,1 coefficients (joint with Lior Bary-Soroker and Gady Kozma)\, a
s well as on results about the concentration of divisors of random integer
s and the size of the Hooley Delta function (joint with Ben Green and Kevi
n Ford).\n
LOCATION:https://researchseminars.org/talk/LNTS/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jef Laga
DTSTART:20210512T150000Z
DTEND:20210512T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/38
DESCRIPTION:Title: Ra
tional points and Selmer groups of genus 3 curves\nby Jef Laga as part
of London number theory seminar\n\n\nAbstract\nManjul Bhargava and Arul S
hankar have determined the average size of the n-Selmer group of the famil
y of all elliptic curves over Q ordered by height\, for n at most 5. They
used this to show that the average rank of elliptic curves is less than on
e. \n\nIn this talk we will consider a family of nonhyperelliptic genus 3
curves\, and bound the average size of the 2-Selmer group of their Jacobia
ns. This implies that a majority of curves in this family have relatively
few rational points. We also consider a family of abelian surfaces which a
re not principally polarized and obtain similar results.\n
LOCATION:https://researchseminars.org/talk/LNTS/38/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anna Medvedovsky
DTSTART:20210526T150000Z
DTEND:20210526T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/39
DESCRIPTION:Title: Co
unting modular forms with fixed mod-p Galois representation and Atkin-Lehn
er-at-p eigenvalue\nby Anna Medvedovsky as part of London number theor
y seminar\n\n\nAbstract\nWork in progress joint with Samuele Anni and Alex
andru Ghitza. For N prime to p\, we count the number of classical modular
forms of level Np and weight k with fixed residual Galois representation a
nd Atkin-Lehner-at-p sign\, generalizing both recent results of Martin gen
eralizing work of Wakatsuki (no residual representation constraint) and th
e rhobar-dimension-counting formulas of Bergdall-Pollack and Jochnowitz. T
o resolve tension between working mod p and the need to invert p\, we use
the trace formula to establish up-to-semisimplifcation isomorphisms betwee
n certain mod-p Hecke\nmodules (namely\, refinements of the weight-filtrat
ion graded pieces W_k) by exhibiting ever-deeper congruences between trace
s of prime-power Hecke operators acting on characteristic-zero Hecke\nmodu
les. This last technique is new\, purely algebraic\, and may be of indepen
dent interest\; it relies on a combinatorial theorem whose proof benefited
from a beautiful boost from Gessel.\n
LOCATION:https://researchseminars.org/talk/LNTS/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lillian Pierce
DTSTART:20210602T150000Z
DTEND:20210602T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/40
DESCRIPTION:Title: Co
unting problems\, from the perspective of moments\nby Lillian Pierce a
s part of London number theory seminar\n\n\nAbstract\nMany questions in nu
mber theory can be phrased as counting problems. How many number fields ar
e there? How many elliptic curves are there? How many integral solutions t
o this system of Diophantine equations are there? If the answer is “infi
nitely many\,” we want to understand the order of growth for the number
of objects we are counting in the “family." But in many settings we are
also interested in finer-grained questions\, like: how many number fields
are there\, with fixed degree and fixed discriminant? We know the answer i
s “finitely many\,” but it would have important consequences if we cou
ld show the answer is always “very few indeed.” In this talk\, we will
describe a way that these finer-grained questions can be related to the b
igger infinite-family questions. Then we will use this perspective to surv
ey interconnections between several big open conjectures in number theory\
, related in particular to class groups and number fields.\n
LOCATION:https://researchseminars.org/talk/LNTS/40/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pip Goodman
DTSTART:20210609T150000Z
DTEND:20210609T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/41
DESCRIPTION:Title: Su
perelliptic curves with large Galois images\nby Pip Goodman as part of
London number theory seminar\n\n\nAbstract\nLet $K$ be a number field. Th
e inverse Galois problem for $K$ asks if for every finite group $G$ there
exists a Galois extension $L/K$ whose Galois group is isomorphic to $G$. M
any people have used torsion points on abelian varieties to realise symple
ctic similitude groups (${\\rm GSp}_n(F_\\ell)$) over $Q$.\n\nIn this talk
\, we examine mod $\\ell$ Galois representations attached to superelliptic
curves and use them to realise general linear and unitary similitude grou
ps over cyclotomic fields. A variety of mathematics is involved\, includin
g group theory\, CM theory\, root discriminant bounds\, and models of curv
es.\n
LOCATION:https://researchseminars.org/talk/LNTS/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pär Kurlberg
DTSTART:20210616T150000Z
DTEND:20210616T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/42
DESCRIPTION:Title: Le
vel repulsion for arithmetic toral point scatterers\nby Pär Kurlberg
as part of London number theory seminar\n\n\nAbstract\nThe Seba billiard w
as introduced to study the transition between\n integrability and chaos
in quantum systems. The model seem to exhibit\n intermediate level sta
tistics with strong repulsion between nearby\n eigenvalues (consistent
with random matrix theory predictions for\n spectra of chaotic systems)
\, whereas large gaps seem to have "Poisson\n tails" (as for spectra of
integrable systems.)\n\n We investigate the closely related "toral poi
nt scatterer"-model\, i.e.\,\n the Laplacian perturbed by a delta-poten
tial\, on 3D tori of the form\n R^3/Z^3. This gives a rank one perturb
ation of the original Laplacian\,\n and it is natural to split the spec
trum/eigenspaces into two parts: the\n "old" (unperturbed) one spanned
by eigenfunctions vanishing at the\n scatterer location\, and the "new"
part (spanned by Green's functions).\n We show that there is strong re
pulsion between the new set of\n eigenvalues.\n
LOCATION:https://researchseminars.org/talk/LNTS/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sug Woo Shin
DTSTART:20210623T100000Z
DTEND:20210623T110000Z
DTSTAMP:20260315T025337Z
UID:LNTS/43
DESCRIPTION:Title: Fr
om Langlands–Rapoport to the trace formula\nby Sug Woo Shin as part
of London number theory seminar\n\n\nAbstract\nIn this talk\, I will repor
t on joint work with Mark Kisin and Yihang Zhu to establish a stabilized t
race formula computing the cohomology of abelian-type Shimura varieties at
a prime of good reduction. As a key intermediate step\, we prove a versio
n of the Langlands-Rapoport conjecture that is more precise than shown in
Kisin’s recent paper.\n
LOCATION:https://researchseminars.org/talk/LNTS/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matt Young (Texas A&M University)
DTSTART:20210421T150000Z
DTEND:20210421T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/44
DESCRIPTION:Title: An
improved spectral large sieve inequality for $\\text{SL}_3(\\mathbb Z)$.<
/a>\nby Matt Young (Texas A&M University) as part of London number theory
seminar\n\n\nAbstract\nI will discuss recent progress on the spectral larg
e sieve problem for $\\text{SL}_3(\\mathbb Z)$. The method of proof uses
duality and its structure reveals unexpected connections to Heath-Brown's
large sieve for cubic characters.\n
LOCATION:https://researchseminars.org/talk/LNTS/44/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Natalie Evans
DTSTART:20210630T150000Z
DTEND:20210630T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/45
DESCRIPTION:Title: Co
rrelations of almost primes\nby Natalie Evans as part of London number
theory seminar\n\n\nAbstract\nThe Hardy-Littlewood generalised twin prime
conjecture states an asymptotic formula for the number of primes $p\\le X
$ such that $p+h$ is prime for any non-zero even integer $h$. While this c
onjecture remains wide open\, Matomaki\, Radziwill and Tao proved that it
holds on average over $h$\, improving on a previous result of Mikawa. In t
his talk we will discuss an almost prime analogue of the Hardy-Littlewood
conjecture for which we can go beyond what is known for primes. We will de
scribe some recent work in which we prove an asymptotic formula for the nu
mber of almost primes $n=p_1p_2 \\le X$ such that $n+h$ has exactly two pr
ime factors which holds for a very short average over $h$.\n
LOCATION:https://researchseminars.org/talk/LNTS/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vaidehee Thatte (King's College London)
DTSTART:20211208T150000Z
DTEND:20211208T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/48
DESCRIPTION:Title: Un
derstanding the Defect via Ramification Theory\nby Vaidehee Thatte (Ki
ng's College London) as part of London number theory seminar\n\nLecture he
ld in Huxley 144\, Imperial.\n\nAbstract\nClassical ramification theory de
als with complete discrete valuation fields $k((X))$ with perfect residue
fields $k$. Invariants such as the Swan conductor capture important inform
ation about extensions of these fields. Many fascinating complications ari
se when we allow non-discrete valuations and imperfect residue fields $k$.
Particularly in positive residue characteristic\, we encounter the myster
ious phenomenon of the defect (or ramification deficiency). The occurrence
of a non-trivial defect is one of the main obstacles to long-standing pro
blems\, such as obtaining resolution of singularities in positive characte
ristic.\n\nDegree p extensions of valuation fields are building blocks of
the general case. In this talk\, we will present a generalization of ramif
ication invariants for such extensions and discuss how this leads to a bet
ter understanding of the defect. If time permits\, we will briefly discuss
their connection with some recent work (joint with K. Kato) on upper rami
fication groups.\n
LOCATION:https://researchseminars.org/talk/LNTS/48/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matteo Tamiozzo (Imperial College London)
DTSTART:20211013T140000Z
DTEND:20211013T150000Z
DTSTAMP:20260315T025337Z
UID:LNTS/50
DESCRIPTION:Title: Pe
rfectoid Jacquet-Langlands and the cohomology of Hilbert modular varieties
\nby Matteo Tamiozzo (Imperial College London) as part of London numbe
r theory seminar\n\nLecture held in Huxley 139\, Imperial.\n\nAbstract\nDe
uring and Serre showed that the supersingular locus in a special fibre of
a modular curve can be identified with a Shimura set attached to a definit
e quaternion algebra. I will discuss a perfectoid version of this result o
ver totally real fields\, comparing the cohomology of fibres of the Hodge-
Tate period maps attached to different quaternionic Shimura varieties. I w
ill then explain how this can be used to prove vanishing theorems for the
cohomology with torsion coefficients of Hilbert modular varieties. This is
joint work with Ana Caraiani.\n
LOCATION:https://researchseminars.org/talk/LNTS/50/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rachel Newton (King's College London)
DTSTART:20211020T140000Z
DTEND:20211020T150000Z
DTSTAMP:20260315T025337Z
UID:LNTS/51
DESCRIPTION:Title: Nu
mber fields with prescribed norms\nby Rachel Newton (King's College Lo
ndon) as part of London number theory seminar\n\nLecture held in Huxley 14
4\, Imperial.\n\nAbstract\nLet $G$ be a finite abelian group\, let $k$ be
a number field\, and let $\\alpha\\in k^\\times$. We count Galois extensio
ns $K/k$ with Galois group $G$ such that $\\alpha$ is a norm from $K/k$.\n
In particular\, we show that such extensions always exist. This is joint w
ork with Christopher\nFrei and Daniel Loughran.\n
LOCATION:https://researchseminars.org/talk/LNTS/51/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chris Williams (University of Warwick)
DTSTART:20211110T150000Z
DTEND:20211110T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/52
DESCRIPTION:Title: $p
$-adic $L$-functions for GL(3)\nby Chris Williams (University of Warwi
ck) as part of London number theory seminar\n\nLecture held in Huxley 144\
, Imperial.\n\nAbstract\nLet $\\pi$ be a $p$-ordinary cohomological cuspid
al automorphic representation of $GL_n(\\mathbb{A}_\\mathbb{Q})$. A conjec
ture of Coates--Perrin-Riou predicts that the (twisted) critical values of
its $L$-function $L(\\pi \\times \\chi\,s)$\, for Dirichlet characters $\
\chi$ of $p$-power conductor\, satisfy systematic congruence properties mo
dulo powers of $p$\, captured in the existence of a $p$-adic $L$-function.
For $n = 1\,2$ this conjecture has been known for decades\, but for $n \\
geq 3$ it is known only in special cases\, e.g. symmetric squares of modul
ar forms\; and in all known cases\, $\\pi$ is a functorial transfer from a
proper subgroup of $GL_n$. I will explain what a $p$-adic $L$-function is
\, state the conjecture more precisely\, and then report on ongoing joint
work with David Loeffler\, in which we prove this conjecture for $n=3$ (wi
thout any transfer or self-duality assumptions).\n
LOCATION:https://researchseminars.org/talk/LNTS/52/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alex Torzewski (King's College London)
DTSTART:20211124T150000Z
DTEND:20211124T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/53
DESCRIPTION:Title: La
wrence-Venkatesh in families\nby Alex Torzewski (King's College London
) as part of London number theory seminar\n\nLecture held in Huxley 144\,
Imperial.\n\nAbstract\nWe outline how the method of Lawrence-Venkatesh can
be used in families to obtain upper bounds on the number of rational poin
ts on curves of genus > 1 depending only on the reduction modulo a well ch
osen prime and the primes of bad reduction. This was first shown by Faltin
gs as a consequence of the Mordell and Shafarevich Conjectures.\n
LOCATION:https://researchseminars.org/talk/LNTS/53/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jack Sempliner (Imperial College London)
DTSTART:20211201T150000Z
DTEND:20211201T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/54
DESCRIPTION:Title: On
the almost-product structure on the moduli of bounded global $G$-shtuka\nby Jack Sempliner (Imperial College London) as part of London number t
heory seminar\n\nLecture held in Huxley 144\, Imperial.\n\nAbstract\nLet $
X$ be an algebraic curve over $\\mathbb{F}_q$ and $G$ be a reductive algeb
raic group over $\\mathbb{F}_q(X)$. Under mild technical hypotheses we con
struct families of stacks over the moduli $\\text{Sht}_{G\, X\, I}^{\\mu_*
}$ of bounded global $G$-shtuka (a small generalization of the stacks stud
ied by Lafforgue and Varshavsky) which provide natural analogues of Igusa
varieties in the function field setting. Our main result is an isomorphism
between certain Igusa varieties associated to moduli of shtuka for reduct
ive groups $G\, G'$ which are related by an inner twist. Along the way we
prove an almost-product formula computing the compactly supported cohomolo
gy of the special fibers of $\\text{Sht}_{G\, X\, I}^{\\mu_*}$ with trivia
l coefficients in terms of the cohomology of our Igusa stacks and a functi
on-field analogue of Rapoport-Zink spaces constructed in previous work of
Hartl and Arasteh Rad.\n
LOCATION:https://researchseminars.org/talk/LNTS/54/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rosa Winter
DTSTART:20211117T150000Z
DTEND:20211117T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/55
DESCRIPTION:Title: De
nsity of rational points on del Pezzo surfaces of degree 1\nby Rosa Wi
nter as part of London number theory seminar\n\nLecture held in Huxley 144
\, Imperial.\n\nAbstract\nDel Pezzo surfaces are surfaces classified by th
eir degree $d$\, which is an integer between 1 and 9 (for $d\\geq3$\, thes
e are the smooth surfaces of degree $d$ in $\\mathbb{P}^d$). For del Pezzo
surfaces of degree at least 2 over a field $k$\, we know that the set of
$k$-rational points is Zariski dense provided that the surface has one $k$
-rational point to start with (that lies outside a specific subset of the
surface for degree 2). However\, for del Pezzo surfaces of degree 1 over a
field $k$\, even though we know that they always contain at least one $k$
-rational point\, we do not know if the set of $k$-rational points is Zari
ski dense in general. I will talk about a result that is joint work with J
ulie Desjardins\, in which we give sufficient conditions for the set of $k
$-rational points on a specific family of del Pezzo surfaces of degree 1 t
o be Zariski dense\, where $k$ is any infinite field of characteristic 0.
These conditions are necessary if $k$ is finitely generated over $\\mathbb
{Q}$. I will compare this to previous results.\n
LOCATION:https://researchseminars.org/talk/LNTS/55/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sarah Zerbes (University College London)
DTSTART:20211103T150000Z
DTEND:20211103T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/56
DESCRIPTION:Title: Eu
ler systems and the BSD conjecture for abelian surfaces\nby Sarah Zerb
es (University College London) as part of London number theory seminar\n\n
Lecture held in Huxley 144\, Imperial.\n\nAbstract\nEuler systems are one
of the most powerful tools for proving cases of the Bloch--Kato conjecture
\, and other related problems such as the Birch and Swinnerton-Dyer conjec
ture. I will recall a series of recent works (variously joint with Loeffle
r\, Pilloni\, Skinner) giving rise to an Euler system in the cohomology of
Shimura varieties for GSp(4)\, and an explicit reciprocity law relating t
his to values of L-functions. I will then explain work in progress with Lo
effler\, in which we use this Euler system to prove new cases of the BSD c
onjecture for modular abelian surfaces over Q\, and modular elliptic curve
s over imaginary quadratic fields.\n
LOCATION:https://researchseminars.org/talk/LNTS/56/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Peter Jossen
DTSTART:20220112T160000Z
DTEND:20220112T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/57
DESCRIPTION:Title: A
non-hypergeometric E-function\nby Peter Jossen as part of London numbe
r theory seminar\n\n\nAbstract\nWith the goal of generalising the theorems
of Hermite\, Lindemann\, and Weierstrass about transcendence of values of
the exponential function\, Siegel\nintroduced the notion of E-function in
his landmark 1929 paper "Über einige Anwendungen diophantischer Approxim
ationen". Hypergeometric functions\nprovide a rich class of E-functions\,
and Siegel asked whether in fact every E-function is a polynomial expressi
on in hypergeometric E-functions. In a\njoint work with Javier Fresán\, w
e answer Siegel's question in the negative.\n
LOCATION:https://researchseminars.org/talk/LNTS/57/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrei Yafaev
DTSTART:20220119T160000Z
DTEND:20220119T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/58
DESCRIPTION:Title: He
ights of special points and the Andre-Oort conjecture\nby Andrei Yafae
v as part of London number theory seminar\n\n\nAbstract\nThe Andre-Oort co
njecture states that components of the Zariski closure of a set of\nspecia
l points in a Shimura variety\, are special subvarieties.\nThis conjecture
has been a subject of active research in \nrecent years.\nThe last remain
ing step was to obtain lower bounds for Galois\ndegrees of special points.
\n\nIn a joint work with Gal Biniyamini and Harry Schmidt\, we have formul
ated a conjecture \non heights of special points and deduced from it the r
equired bounds.\nVery recently\, J.Pila\, A.Shankar and J.Tsimerman \nanno
unced a proof of our height conjecture\, thus completing the proof\nof the
Andre-Oort conjecture in full generality.\n
LOCATION:https://researchseminars.org/talk/LNTS/58/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Caleb Springer
DTSTART:20220126T160000Z
DTEND:20220126T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/59
DESCRIPTION:Title: Ev
ery finite abelian group arises as the group of rational points of an ordi
nary abelian variety over $\\mathbb{F}_2$\, $\\mathbb{F}_3$\, and $\\math
bb{F}_5$\nby Caleb Springer as part of London number theory seminar\n\
n\nAbstract\nWe will show that every finite abelian group arises as the gr
oup of rational points of an ordinary abelian variety over a finite field
with 2\, 3 or 5 elements. Similar results hold over finite fields of larg
er cardinality. On our way to proving these results\, we will view the gr
oup of rational points of an abelian variety as a module over its endomorp
hism ring. By describing this module structure in important cases\, we obt
ain (a fortiori) an understanding of the underlying groups. Combining this
description of structure with recent results on the cardinalities of grou
ps of rational points of abelian varieties over finite fields\, we will de
duce the main theorem. This work is joint with Stefano Marseglia.\n
LOCATION:https://researchseminars.org/talk/LNTS/59/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alex Walker
DTSTART:20220202T160000Z
DTEND:20220202T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/60
DESCRIPTION:Title: Th
e Average Number of Divisors of the Output of a Quadratic Polynomial\n
by Alex Walker as part of London number theory seminar\n\n\nAbstract\nLet
$d(n)$ count the number of divisors of $n$. In 1963\, Hooley studied parti
al sums $n < X$ of $d(n^2+h)$ and showed that the result was asymptotic to
$c X \\log X + c' X + O(X^{8/9})$ as $X$ tends to infinity (assuming $h$
not a negative square). In other words\, the irreducible polynomial $Q(x)
= x^2 + h$ has outputs with\, on average\, $\\sim \\log x$ many divisors.
Hooley's error bound was improved by Bykoskii in 1987 to $O(X^{2/3})$ usin
g the spectral theory of automorphic forms. This talk describes a new proo
f of Bykovskii's result in a new framework\, now using Dirichlet series an
d automorphic forms of half-integral weight. This new framework has limita
tions but is also quite flexible. To demonstrate this\, we develop in tand
em counts for the average number of divisors of $Q(x\,y) = x^2+y^2+h$ for
$x^2+y^2+h < X$.\n
LOCATION:https://researchseminars.org/talk/LNTS/60/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sam Streeter
DTSTART:20220209T160000Z
DTEND:20220209T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/61
DESCRIPTION:Title: We
ak approximation for del Pezzo surfaces of low degree\nby Sam Streeter
as part of London number theory seminar\n\n\nAbstract\nConjecturally\, th
e rational points of a del Pezzo surface over a number field are well-dist
ributed among the local points over all but finitely completions of the gr
ound field—that is\, the surface satisfies weak weak approximation. Howe
ver\, describing the rational points becomes harder as the degree of the d
el Pezzo surface decreases. As such\, many questions remain unanswered for
del Pezzo surfaces of low degree. In this talk\, I will report on recent
joint work with Julian Demeio\, in which we prove that del Pezzo surfaces
of degrees 1 and 2 satisfy weak weak approximation\, provided that we assu
me some additional geometric structure in the form of conic fibrations.\n
LOCATION:https://researchseminars.org/talk/LNTS/61/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nirvana Coppola (Vrije Universiteit Amsterdam)
DTSTART:20220223T160000Z
DTEND:20220223T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/62
DESCRIPTION:Title: Co
leman integrals over number fields: a computational approach\nby Nirva
na Coppola (Vrije Universiteit Amsterdam) as part of London number theory
seminar\n\n\nAbstract\nOne of the deepest mathematical results is Faltings
's Theorem on the finiteness of rational points on an algebraic curve of g
enus $g \\geq 2$. A much more difficult question\, still not completely an
swered\, is whether given a curve of genus $g \\geq 2$\, we can find all i
ts rational points\, or\, more in general\, all points defined over a cert
ain number field. An entire (currently very active!) area of research is d
evoted to find an answer to such questions\, using the "method of Chabauty
".\n\nIn this seminar\, I will talk about one of the first tools employed
in Chabauty method\, namely Coleman integrals\, which Coleman used to comp
ute an explicit bound on the number of rational points on a curve. After e
xplaining how this is defined\, I will give a generalisation of this defin
ition for curves defined over number fields\, and explain how to explicitl
y compute these integrals. This is based on an ongoing project\, which sta
rted during the Arizona Winter School 2020\, joint with E. Kaya\, T. Kelle
r\, N. Müller\, S. Muselli.\n
LOCATION:https://researchseminars.org/talk/LNTS/62/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Miriam Norris (King's College London)
DTSTART:20220302T160000Z
DTEND:20220302T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/63
DESCRIPTION:Title: La
ttice graphs for representations of $GL_3(\\F_p)$\nby Miriam Norris (K
ing's College London) as part of London number theory seminar\n\n\nAbstrac
t\nIn a recent paper Le\, Le Hung\, Levin and Morra proved a generalisatio
n of Breuil's Lattice conjecture in dimension three. This involved showing
that lattices inside representations of $GL_3(\\F_p)$ coming from both a
global and a local construction coincide. Motivated by this we consider th
e following graph. For an irreducible representation $\\tau$ of a group $G
$ over a finite extension $K$ of $\\Q_p$ we define a graph on the $\\mathc
al{O}_K$-lattices inside $\\tau$ whose edges encapsulate the relationship
between lattices in terms of irreducible modular representations of $G$ (o
r Serre weights in the context of the paper by Le et al.). \n\nIn this tal
k\, I will demonstrate how one can apply the theory of graduated orders an
d their lattices\, established by Zassenhaus and Plesken\, to understand t
he lattice graphs of residually multiplicity free representation over suit
ably large fields in terms of a matrix called an exponent matrix. Furtherm
ore I will explain how I have been able to show that one can determine the
exponent matrices for suitably generic representation go $GL_3(\\F_p)$ al
lowing us to construct their lattice graphs.\n
LOCATION:https://researchseminars.org/talk/LNTS/63/
END:VEVENT
BEGIN:VEVENT
SUMMARY:María Inés de Frutos Fernández (Imperial College London)
DTSTART:20220309T160000Z
DTEND:20220309T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/64
DESCRIPTION:Title: Fo
rmalizing the ring of adèles and some applications in Lean\nby María
Inés de Frutos Fernández (Imperial College London) as part of London nu
mber theory seminar\n\n\nAbstract\nI will present a formalization of the r
ing of adèles and group of idèles of a global field in the Lean 3 theore
m prover. Lean is an interactive theorem prover with an ever-growing mathe
matics library. I will give a quick introduction to Lean and explain how t
hese definitions were formalized\, with a focus on the kind of decisions o
ne has to make during the formalization process.\n\nBesides the definition
of the adèles\, we will discuss the formalization of applications includ
ing the statement of the main theorem of global class field theory and a p
roof that the ideal class group of a number field is isomorphic to an expl
icit quotient of its idèle class group.\n
LOCATION:https://researchseminars.org/talk/LNTS/64/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Robert Rockwood (University of Warwick)
DTSTART:20220316T160000Z
DTEND:20220316T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/65
DESCRIPTION:Title: Sp
herical varieties and non-ordinary families of cohomology classes\nby
Robert Rockwood (University of Warwick) as part of London number theory se
minar\n\n\nAbstract\nThe theory of norm compatible cohomology classes is o
f fundamental importance in Iwasawa theory\, encompassing both the theory
of Euler systems and p-adic L-functions. Loeffler has developed a systemat
ic approach to constructing norm-compatible classes using the theory of sp
herical varieties. We show that classes constructed in this way vary natur
ally in Coleman families and give some concrete applications.\n
LOCATION:https://researchseminars.org/talk/LNTS/65/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michael Magee
DTSTART:20220323T160000Z
DTEND:20220323T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/66
DESCRIPTION:Title: Th
e maximal spectral gap of a hyperbolic surface\nby Michael Magee as pa
rt of London number theory seminar\n\n\nAbstract\nA hyperbolic surface is
a surface with metric of constant curvature -1. The spectral gap between\n
the first two eigenvalues of the Laplacian on a closed hyperbolic surface
contains a good deal of\ninformation about the surface\, including its con
nectivity\, dynamical properties of its geodesic flow\,\nand error terms i
n geodesic counting problems. For arithmetic hyperbolic surfaces the spect
ral gap\nis also the subject of one of the biggest open problems in automo
rphic forms: Selberg’s eigenvalue\nconjecture.\nIt was an open problem f
rom the 1970s whether there exist a sequence of closed hyperbolic sur-\nfa
ces with genera tending to infinity and spectral gap tending to 1/4. (The
value 1/4 here is the\nasymptotically optimal one.) Recently we proved tha
t this is indeed possible. I’ll discuss the very\ninteresting background
of this problem in detail as well as some ideas of the proof. This is joi
nt work\nwith Will Hide.\n
LOCATION:https://researchseminars.org/talk/LNTS/66/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alex Best (VU Amsterdam)
DTSTART:20220427T150000Z
DTEND:20220427T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/67
DESCRIPTION:Title: Th
e S-unit equation and non-abelian Chabauty in depth 2\nby Alex Best (V
U Amsterdam) as part of London number theory seminar\n\nLecture held in Bu
sh House S2.03\, King's College London.\n\nAbstract\nThe S-unit equation i
s a classical and well-studied Diophantine equation\, with numerous connec
tions to other Diophantine problems.\nRecent work of Kim and refinements d
ue to Betts-Dogra have suggested new cohomological strategies to find rati
onal and integral points on curves\, based on but massively extending the
classical method of Chabauty. At present\, these methods are only conjectu
rally guaranteed to succeed in general\, but they promise several applicat
ions in arithmetic geometry if they could be proved to always work.\nIn or
der to better understand the conjectures of Kim that suggest that this met
hod should work\, we consider the case of the thrice punctured projective
line\, in "depth 2"\, the "smallest" non-trivial extension of the classica
l method. In doing so we get very explicit results for some S-unit equatio
ns\, demonstrating the usability of the aforementioned cohomological metho
ds in this setting. To do this we determine explicitly equations for (maps
between) the (refined) Selmer schemes defined by Kim\, and Betts-Dogra\,
which turn out to have some particularly simple forms.\nThis is joint work
with Alexander Betts\, Theresa Kumpitsch\, Martin Lüdtke\, Angus McAndre
w\, Lie Qian\, Elie Studnia\, and Yujie Xu .\n
LOCATION:https://researchseminars.org/talk/LNTS/67/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aled Walker (King's College London)
DTSTART:20220504T150000Z
DTEND:20220504T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/68
DESCRIPTION:Title: Co
rrelations of sieve weights and distributions of zeros\nby Aled Walker
(King's College London) as part of London number theory seminar\n\nLectur
e held in King's Building K0.18\, King's College London.\n\nAbstract\nIn t
his talk we will discuss Montgomery's pair correlation conjecture for the
zeros of the Riemann zeta function. This is a deep spectral conjecture\, c
losely related to several arithmetic conjectures on the distribution of pr
imes. For example\, even assuming a strong form of the twin prime conjectu
re\, one would only resolve Montgomery's conjecture in a limited range. Ye
t\, building on work of Goldston and Gonek from the late 1990s\, we will p
resent a recent conditional lower bound on the Fourier transform of Montgo
mery's pair correlation function\, valid under milder hypotheses. The new
technical ingredient is a correlation estimate for the Selberg sieve weigh
ts\, for which the level of support of the weights lies beyond the classic
al square-root barrier.\n
LOCATION:https://researchseminars.org/talk/LNTS/68/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Peter Zenz (McGill)
DTSTART:20220511T150000Z
DTEND:20220511T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/69
DESCRIPTION:Title: Ho
lomorphic Hecke Cusp Forms and Quantum Chaos\nby Peter Zenz (McGill) a
s part of London number theory seminar\n\nLecture held in King's Building\
, K0.18.\n\nAbstract\nArithmetic Quantum Chaos (AQC) is an active area of
research at the intersection of number theory and physics. One major goal
in AQC is to study the mass distribution and behaviour of Hecke Maass cusp
forms on hyperbolic surfaces as the Laplace eigenvalue tends to infinity.
In this talk we will focus on analogous questions for holomorphic Hecke c
usp forms. First\, we will review some of the important solved and unsolve
d questions in the area\, like the Quantum Unique Ergodicity problem or th
e Gaussian Moment Conjecture. We then elaborate on a sharp bound for the f
ourth moment of holomorphic cusp forms and ongoing work on evaluating the
averaged sixth moment of holomorphic cusp forms. These are special instanc
es of the Gaussian Moment Conjecture.\n
LOCATION:https://researchseminars.org/talk/LNTS/69/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emilia Alvarez (Bristol)
DTSTART:20220518T150000Z
DTEND:20220518T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/70
DESCRIPTION:Title: Mo
ment computations in the classical compact ensembles\nby Emilia Alvare
z (Bristol) as part of London number theory seminar\n\n\nAbstract\nAfter a
brief introduction on the random matrix applications to number theory\, I
will present a collection of moment computations over the unitary\, sympl
ectic and special orthogonal random matrix ensembles that I've done throug
hout my thesis. I will highlight work on the asymptotics of moments of the
logarithmic derivative of characteristic polynomials evaluated near the p
oint 1. Throughout\, the focus will be on the methods used\, the motivatio
n from number theory and directions for future work.\n
LOCATION:https://researchseminars.org/talk/LNTS/70/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Justin Trias-Batle (Imperial College London)
DTSTART:20220525T150000Z
DTEND:20220525T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/71
DESCRIPTION:Title: To
wards a theta correspondence in families for type II dual pairs\nby Ju
stin Trias-Batle (Imperial College London) as part of London number theory
seminar\n\nLecture held in K0.18 King's building KCL.\n\nAbstract\nThis i
s current work with Gil Moss. The classical local theta correspondence for
p-adic reductive dual pairs defines a bijection between prescribed subset
s of irreducible smooth complex representations coming from two groups (H\
,H')\, forming a dual pair in a symplectic group. Alberto Mínguez extende
d this result for type II dual pairs\, i.e. when (H\,H') is made of genera
l linear groups\, to representations with coefficients in an algebraically
closed field of characteristic l as long as the characteristic l does not
divide the pro-orders of H and H'. For coefficients rings like Z[1/p]\, w
e explain how to build a theory in families for type II dual pairs that is
compatible with reduction to residue fields of the base coefficient ring\
, where central to this approach is the integral Bernstein centre. We tran
slate some weaker properties of the classical correspondence\, such as com
patibility with supercuspidal support\, as a morphism between the integral
Bernstein centres of H and H' and interpret it for the Weil representatio
n. In general\, we only know that this morphism is finite though we may ex
pect it to be surjective. This would result in a closed immersion between
the associated affine schemes as well as a correspondence between characte
rs of the Bernstein centre.\n
LOCATION:https://researchseminars.org/talk/LNTS/71/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Raman Parimala (Emory)
DTSTART:20220601T150000Z
DTEND:20220601T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/72
DESCRIPTION:Title: Th
e Brauer group of hyperelliptic curves over number fields\nby Raman Pa
rimala (Emory) as part of London number theory seminar\n\nLecture held in
King's building K0.18\, King's College London.\n\nAbstract\nWe discuss per
iod-index bounds for the unramified Brauer group of function fields of hyp
erelliptic curves over number fields. We describe a link to the question
of Hasse principle for smooth intersection of quadrics.\n
LOCATION:https://researchseminars.org/talk/LNTS/72/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sacha Mangerel (Durham)
DTSTART:20220615T150000Z
DTEND:20220615T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/73
DESCRIPTION:Title: Ga
ussian distribution of squarefree and B-free numbers in short intervals\nby Sacha Mangerel (Durham) as part of London number theory seminar\n\nL
ecture held in Room K0.18 in the King's Building.\n\nAbstract\n(Joint with
O. Gorodetsky and B. Rodgers) It is of classical interest in analytic num
ber theory to understand the fine-scale distribution of arithmetic sequenc
es such as the primes. For a given length scale h\, the number of elements
of a ``nice'' sequence in a uniformly randomly selected interval $(x\,x+h
]\, 1 \\leq x \\leq X$\, might be expected to follow the statistics of a n
ormally distributed random variable (in suitable ranges of $1 \\leq h \\le
q X$). Following the work of Montgomery and Soundararajan\, this is known
to be true for the primes\, but only if we assume several deep and long-s
tanding conjectures among which the Riemann Hypothesis. \n\nAs a model for
the primes\, in this talk I will address such statistical questions for t
he sequence of squarefree numbers\, i.e.\, numbers not divisible by the sq
uare of any prime\, among other related ``sifted'' sequences called B-free
numbers. I hope to further motivate and explain our main result that show
s\, unconditionally\, that short interval counts of squarefree numbers do
satisfy Gaussian statistics\, answering several questions of R.R. Hall.\n
LOCATION:https://researchseminars.org/talk/LNTS/73/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lassina Dembele (King's College London)
DTSTART:20220622T150000Z
DTEND:20220622T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/74
DESCRIPTION:Title: Ex
plicit inertial local Langlands correspondence for ${\\rm GL_2}$ and arith
metic applications\nby Lassina Dembele (King's College London) as part
of London number theory seminar\n\n\nAbstract\nIn this talk\, we describe
an algorithm for computing automorphic and inertial types for ${\\rm GL_2
}$\, and gives several applications. (This is joint work with Nuno Freitas
and John Voight.)\n
LOCATION:https://researchseminars.org/talk/LNTS/74/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yukako Kezuka (Jussieu)
DTSTART:20220629T150000Z
DTEND:20220629T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/75
DESCRIPTION:Title: Ar
ithmetic of elliptic curves with complex multiplication at small primes\nby Yukako Kezuka (Jussieu) as part of London number theory seminar\n\nL
ecture held in King's Building K0.18.\n\nAbstract\nThe equation E: x^3+y^3
=N defines a classical family of elliptic curves as N varies over cube-fre
e positive integers. They admit complex multiplication\, which allows us t
o tackle the conjecture of Birch and Swinnerton-Dyer for E effectively. In
deed\, using Iwasawa theory\, Rubin was able to show the p-part of the con
jecture for E for all primes p\, except for the primes 2 and 3. The theory
becomes much more complex at these small primes\, but at the same time we
can observe some interesting phenomena. I will explain a method to study
the p-adic valuation of the algebraic part of the central L-value of E\, a
nd I will establish the 3-part of the conjecture for E in special cases. I
will then explain a relation between the 2-part of a certain ideal class
group and the Tate-Shafarevich group of E. Part of this talk is based on j
oint work with Yongxiong Li.\n
LOCATION:https://researchseminars.org/talk/LNTS/75/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Si Ying Lee (MPIM Bonn)
DTSTART:20221012T150000Z
DTEND:20221012T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/76
DESCRIPTION:Title: Ei
chler-Shimura relations of Hodge type Shimura varieties\nby Si Ying Le
e (MPIM Bonn) as part of London number theory seminar\n\nLecture held in L
ecture held in Huxley 144\, Imperial.\n\nAbstract\nThe well-known classica
l Eichler-Shimura relation for modular curves asserts that the Hecke opera
tor $T_p$ is equal\, as an algebraic correspondence over the special fiber
\, to the sum of Frobenius and Verschiebung. Blasius and Rogawski proposed
a generalization of this result for Shimura varieties with good reduction
at $p$\, and conjectured that the Frobenius satisfies a certain Hecke pol
ynomial. I will talk about a recent proof of this for some Shimura varieti
es of Hodge type.\n
LOCATION:https://researchseminars.org/talk/LNTS/76/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Peiyi Cui (University of East Anglia)
DTSTART:20221102T160000Z
DTEND:20221102T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/77
DESCRIPTION:Title: A
decomposition of the category of l-modular representations of SL_n(F).
\nby Peiyi Cui (University of East Anglia) as part of London number theory
seminar\n\nLecture held in Huxley 139\, Imperial.\n\nAbstract\nLet F be a
p-adic field\, and k an algebraically closed field of characteristic l di
fferent from p. In this talk\, we will first give a category decomposition
of Rep_k(SL_n(F))\, the category of smooth k-representations of SL_n(F)\,
with respect to the GL_n(F)-equivalent supercuspidal classes of SL_n(F)\,
which is not always a block decomposition in general. We then give a bloc
k decomposition of the supercuspidal subcategory\, by introducing a partit
ion on each GL_n(F)-equivalent supercuspidal class through type theory\, a
nd we interpret this partition by the sense of l-blocks of finite groups.
We give an example where a block of Rep_k(SL_2(F)) is defined with respect
to several SL_2(F)-equivalent supercuspidal classes\, which is different
from the case where l is zero. We end this talk by giving a prediction on
the block decomposition of Rep_k(A) for a general p-adic group A.\n
LOCATION:https://researchseminars.org/talk/LNTS/77/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yu Min (Imperial College London)
DTSTART:20221116T160000Z
DTEND:20221116T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/78
DESCRIPTION:Title: Ho
dge--Tate crystals and Sen theory\nby Yu Min (Imperial College London)
as part of London number theory seminar\n\nLecture held in Huxley 139\, I
mperial.\n\nAbstract\nLet $K$ be a finite extension of $\\mathbb Q_p$. Bha
tt and Scholze have proved that the category of prismatic $F$-crystals on
the absolute prismatic site of $\\mathcal O_K$ is equivalent to the catego
ry of crystalline $\\mathbb Z_p$-representations of the absolute Galois gr
oup of $K$. In this talk\, we will instead consider the (rational) Hodge--
Tate crystals on the absolute prismatic site of $\\mathcal O_K$ or more ge
nerally of a smooth $p$-adic formal scheme. We will show how Hodge--Tate c
rystals are related to the Sen theory. If time permits\, we will also disc
uss its application in the arithmetic $p$-adic Simpson correspondence. Thi
s is joint work with Yupeng Wang.\n
LOCATION:https://researchseminars.org/talk/LNTS/78/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jeff Manning (Imperial College London)
DTSTART:20221123T160000Z
DTEND:20221123T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/79
DESCRIPTION:Title: Th
e Wiles-Lenstra-Diamond numerical criterion over imaginary quadratic field
s\nby Jeff Manning (Imperial College London) as part of London number
theory seminar\n\nLecture held in Huxley 139\, Imperial.\n\nAbstract\nWile
s' modularity lifting theorem was the central argument in his proof of mod
ularity of (semistable) elliptic curves over Q\, and hence of Fermat's Las
t Theorem. His proof relied on two key components: his "patching" argument
(developed in collaboration with Taylor) and his numerical isomorphism cr
iterion.\n\nIn the time since Wiles' proof\, the patching argument has bee
n generalized extensively to prove a wide variety of modularity lifting re
sults. In particular Calegari and Geraghty have found a way to generalize
it to prove potential modularity of elliptic curves over imaginary quadrat
ic fields (contingent on some standard conjectures). The numerical criteri
on on the other hand has proved far more difficult to generalize\, althoug
h in situations where it can be used it can prove stronger results than wh
at can be proven purely via patching.\n\nIn this talk I will present joint
work with Srikanth Iyengar and Chandrashekhar Khare which proves a genera
lization of the numerical criterion to the context considered by Calegari
and Geraghty (and contingent on the same conjectures). This allows us to p
rove integral "R=T" theorems at non-minimal levels over imaginary quadrati
c fields\, which are inaccessible by Calegari and Geraghty's method. The r
esults provide new evidence in favor of a torsion analog of the classical
Langlands correspondence.\n
LOCATION:https://researchseminars.org/talk/LNTS/79/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Toby Gee (IC)
DTSTART:20221130T160000Z
DTEND:20221130T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/80
DESCRIPTION:Title: Co
ngruences between modular forms and the categorical p-adic Langlands progr
am\nby Toby Gee (IC) as part of London number theory seminar\n\nLectur
e held in Huxley 139\, Imperial.\n\nAbstract\nI will attempt to give a gen
tle introduction to the categorical p-adic Langlands program and its conne
ctions to questions about congruences between modular forms.\n
LOCATION:https://researchseminars.org/talk/LNTS/80/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hanneke Wiersema (University of Cambridge)
DTSTART:20221207T160000Z
DTEND:20221207T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/81
DESCRIPTION:Title: Mo
dularity in the partial weight one case\nby Hanneke Wiersema (Universi
ty of Cambridge) as part of London number theory seminar\n\nLecture held i
n Huxley 139\, Imperial.\n\nAbstract\nThe strong form of Serre's conjectur
e states that a two-dimensional mod $p$ representation of the absolute Gal
ois group of $\\mathbb{Q}$ arises from a modular form of a specific weight
\, level and character. Serre restricted to modular forms of weight at lea
st 2\, but Edixhoven later refined this conjecture to include weight one m
odular forms. In this talk we explore analogues of Edixhoven's refinement
for Galois representations of totally real fields\, extending recent work
of Diamond–-Sasaki. In particular\, we show how modularity of partial we
ight one Hilbert modular forms can be related to modularity of Hilbert mod
ular forms with regular weights\, and vice versa. Time permitting\, we wil
l also discuss a $p$-adic Hodge theoretic version of this.\n
LOCATION:https://researchseminars.org/talk/LNTS/81/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rong Zhou (University of Cambridge)
DTSTART:20221214T160000Z
DTEND:20221214T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/82
DESCRIPTION:Title: In
dependence of $\\ell$ for $G$-valued Weil--Deligne representations associa
ted to abelian varieties\nby Rong Zhou (University of Cambridge) as pa
rt of London number theory seminar\n\nLecture held in Huxley 139\, Imperia
l.\n\nAbstract\nLet $A$ be an abelian variety over a number field $E$ of d
imension $g$ and $\\rho_\\ell:\\mathrm{Gal}(\\overline{E}/E)\\rightarrow \
\mathrm{GL}_{2g}(\\mathbb{Q}_\\ell)$ the Galois representation on the $\\e
ll$-adic Tate module of $A$. For a place $v$ of $E$ not dividing $\\ell$\,
upon fixing an isomorphism $\\overline{\\mathbb{Q}}_\\ell\\cong \\mathbb{
C}$\, Grothendieck’s $\\ell$-adic monodromy theorem associates to $\\rho
_\\ell$ a $\\mathrm{GL}_{2g}(\\mathbb{C})$-valued Weil-Deligne representat
ion $\\rho_{\\ell\,v}^{WD}$. Then it is known that the conjugacy class of
$\\rho_{\\ell\,v}^{WD}$ is defined over $\\mathbb{Q}$ and independent of $
\\ell.$ When $v$ is a place a good reduction\, this is just the result tha
t the characteristic polynomial of Frobenius is defined over $\\mathbb{Z}$
and independent of $\\ell$.\n\nWe consider a refinement of this result. A
Theorem of Deligne implies that upon replacing $E$ by a finite extension\
, the representations $\\rho_{\\ell\,v}^{WD}$ can be refined to a $G(\\mat
hbb{C})$-valued Weil-Deligne representation $\\rho^{WD\,G}_{\\ell\,v}$\, w
here $G$ is the Mumford--Tate group of $A$. We prove that for $p>2$ and $v
|p$ a place of $E$ where $A$ has semistable reduction\, the conjugacy clas
s of $\\rho^{WD\,G}_{\\ell\,v}$ is defined over $\\mathbb{Q}$ and independ
ent of $\\ell$. This is joint work with Mark Kisin.\n
LOCATION:https://researchseminars.org/talk/LNTS/82/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jack Thorne (University of Cambridge)
DTSTART:20221026T150000Z
DTEND:20221026T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/83
DESCRIPTION:Title: Sy
mmetric power functoriality for Hilbert modular forms\nby Jack Thorne
(University of Cambridge) as part of London number theory seminar\n\nLectu
re held in Huxley 139\, Imperial.\n\nAbstract\nSymmetric power functoriali
ty is one of the basic cases of Langlands' functoriality conjectures and i
s the route to the proof of the Sato-Tate conjecture (concerning the distr
ibution of the modulo $p$ point counts of an elliptic curve over $\\mathbb
{Q}$\, as the prime $p$ varies).\n\nI will discuss the proof of the existe
nce of the symmetric power liftings of Hilbert modular forms of regular we
ight. This is joint work with James Newton.\n
LOCATION:https://researchseminars.org/talk/LNTS/83/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chung-Hang (Kevin) Kwan (University College London (UCL))
DTSTART:20221019T150000Z
DTEND:20221019T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/84
DESCRIPTION:Title: Mo
ments and Periods for GL(3)\nby Chung-Hang (Kevin) Kwan (University Co
llege London (UCL)) as part of London number theory seminar\n\nLecture hel
d in Huxley 144\, Imperial.\n\nAbstract\nIn the past century\, moments of
L-functions have been important in number theory and are well-motivated by
a variety of arithmetic applications. In this talk\, we will begin with t
wo elementary counting problems of Diophantine nature as motivation\, foll
owed by a survey of techniques in the past and the present. The main goal
is to demonstrate how period integrals can be used to study moments of aut
omorphic L-functions and uncover the interesting underlying structures (so
me of them can be modeled by random matrix theory).\n
LOCATION:https://researchseminars.org/talk/LNTS/84/
END:VEVENT
BEGIN:VEVENT
SUMMARY:George Boxer (Imperial College London)
DTSTART:20221109T160000Z
DTEND:20221109T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/85
DESCRIPTION:Title: Hi
gher Hida theory for Siegel modular varieties\nby George Boxer (Imperi
al College London) as part of London number theory seminar\n\nLecture held
in Huxley 139\, Imperial.\n\nAbstract\nThe goal of higher Hida theory is
to study the ordinary part of coherent cohomology of Shimura varieties int
egrally. We introduce a higher coherent cohomological analog of Hida's sp
ace of ordinary p-adic modular forms\, which is defined as the "ordinary p
art" of the coherent cohomology with "partial compact support" of the ordi
nary Igusa variety. Then we give an analog of Hida's classicality theorem
in this setting. This is joint work with Vincent Pilloni.\n
LOCATION:https://researchseminars.org/talk/LNTS/85/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Holly Green (University College London)
DTSTART:20230111T160000Z
DTEND:20230111T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/86
DESCRIPTION:Title: An
arithmetic analogue of the parity conjecture\nby Holly Green (Univers
ity College London) as part of London number theory seminar\n\nLecture hel
d in Rm. 505\, UCL Department of Mathematics (UCL Union Building).\n\nAbst
ract\nI will present a new method to compute the parity of the rank of an
elliptic curve and will comment on how this construction generalises to Ja
cobians of curves. This method involves studying the local arithmetic atta
ched to covers of the curve. In addition\, I will discuss applications to
the Birch and Swinnerton-Dyer conjecture\, including a new proof of the pa
rity conjecture for elliptic curves. This is joint work with Vladimir Dokc
hitser\, Alexandros Konstantinou\, Céline Maistret and Adam Morgan.\n
LOCATION:https://researchseminars.org/talk/LNTS/86/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Akshat Mudgal (University of Oxford)
DTSTART:20230118T160000Z
DTEND:20230118T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/87
DESCRIPTION:Title: Ad
ditive equations over lattice points on spheres\nby Akshat Mudgal (Uni
versity of Oxford) as part of London number theory seminar\n\nLecture held
in Rm. 706\, UCL Department of Mathematics (UCL Union Building).\n\nAbstr
act\nIn this talk\, we will consider additive properties of lattice points
on spheres. Thus\, defining $S_m$ to be the set of lattice points on the
sphere $x^2 + y^2 + z^2 + w^2 = m$\, we are interested in counting the num
ber of solutions to the equation\n$$a_1 + a_2 = a_3 + a_4\,$$\nwhere $a_1\
,\\dots\, a_4$ lie in some arbitrary subset $A$ of $S_m$. Such an inquiry
is closely related to various problems in harmonic analysis and analytic n
umber theory\, including Bourgain's discrete restriction conjecture for sp
heres. We will survey some recent results in this direction\, as well as d
escribe some of the various techniques\, arising from areas such as incide
nce geometry\, analytic number theory and arithmetic combinatorics\, that
have been employed to tackle this type of problem.\n
LOCATION:https://researchseminars.org/talk/LNTS/87/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jens Funke (Durham University)
DTSTART:20230125T160000Z
DTEND:20230125T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/88
DESCRIPTION:Title: In
definite theta series via incomplete theta integrals\nby Jens Funke (D
urham University) as part of London number theory seminar\n\nLecture held
in Rm. 706\, UCL Department of Mathematics (UCL Union Building).\n\nAbstra
ct\nPositive definite theta series have been a classical tool in the arith
metic of quadratic forms and also in the theory of modular forms. In compa
rison\, the indefinite case has been less studied. \nIn this talk we will
explain how indefinite theta series naturally arise in the context of symm
etric spaces of orthogonal type and discuss recent developments inspired b
y mathematical physics. This is joint work with Steve Kudla.\n
LOCATION:https://researchseminars.org/talk/LNTS/88/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Min Lee (University of Bristol)
DTSTART:20230201T160000Z
DTEND:20230201T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/89
DESCRIPTION:Title: An
extension of converse theorems to the Selberg class\nby Min Lee (Univ
ersity of Bristol) as part of London number theory seminar\n\nLecture held
in Rm. 706\, UCL Department of Mathematics (UCL Union Building).\n\nAbstr
act\nThe converse theorem for automorphic forms has a long history beginni
ng with the work of Hecke (1936) and a work of Weil (1967): relating the a
utomorphy relations satisfied by classical modular forms to analytic prope
rties of their L-functions and the L-functions twisted by Dirichlet charac
ters. The classical converse theorems were reformulated and generalised in
the setting of automorphic representations for GL(2) by Jacquet and Langl
ands (1970). Since then\, the converse theorem has been a cornerstone of t
he theory of automorphic representations. \n\nVenkatesh (2002)\, in his th
esis\, gave new proof of the classical converse theorem for modular forms
of level 1 in the context of Langlands’ “Beyond Endoscopy”. In this
talk\, we extend Venkatesh’s proof of the converse theorem to forms of a
rbitrary levels and characters with the gamma factors of the Selberg class
type. \n\n\nThis is joint work with Andrew R. Booker and Michael Farmer.\
n
LOCATION:https://researchseminars.org/talk/LNTS/89/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pak-Hin Lee (University of Leicester and University of Warwick)
DTSTART:20230301T160000Z
DTEND:20230301T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/90
DESCRIPTION:Title: On
the p-adic interpolation of Asai L-values\nby Pak-Hin Lee (University
of Leicester and University of Warwick) as part of London number theory s
eminar\n\nLecture held in Rm. 706\, UCL Department of Mathematics (UCL Uni
on Building).\n\nAbstract\nOne theme of the relative Langlands program is
that period integrals of an automorphic representation of $G$ over a subgr
oup $H$ often detect functorial transfer from some other group $G'$\; more
over\, such period integrals often compute special $L$-values. It is natur
al to expect $p$-adic $L$-functions interpolating these period integrals a
s the automorphic representation varies in $p$-adic families\, which shoul
d encode geometric information about the eigenvariety of $G$. In this talk
\, we consider the case of Flicker--Rallis periods\, where $G = \\mathrm{G
L}_n(K)$ and $H = \\mathrm{GL}_n(\\mathbf{Q})$ for an imaginary quadratic
field $K$\, and outline the construction of a $p$-adic $L$-function on the
eigenvariety of $G$ interpolating certain non-critical Asai $L$-values. T
his is work in progress with Daniel Barrera Salazar and Chris Williams.\n
LOCATION:https://researchseminars.org/talk/LNTS/90/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sarah Arpin (Leiden University)
DTSTART:20230315T160000Z
DTEND:20230315T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/91
DESCRIPTION:Title: Ad
ding Level Structure to Supersingular Elliptic Curve Isogeny Graphs\nb
y Sarah Arpin (Leiden University) as part of London number theory seminar\
n\nLecture held in Rm. 706\, UCL Department of Mathematics (UCL Union Buil
ding).\n\nAbstract\nThe classical Deuring correspondence provides a roadma
p between supersingular elliptic curves and the maximal orders which are i
somorphic to their endomorphism rings. Building on this idea\, we add the
information of a cyclic subgroup of prime order $N$ to supersingular ellip
tic curves\, and prove a generalisation of the Deuring correspondence for
these objects. We also study the resulting $\\ell$-isogeny graphs supersin
gular elliptic curve with level-$N$ structure\, and the corresponding grap
hs in the realm of quaternion algebras. The structure of the supersingular
elliptic curve ell-isogeny graph underlies the security of a new cryptogr
aphic signature protocol\, SQISign\, which is proposed to be resistant aga
inst both classical and quantum attack.\n
LOCATION:https://researchseminars.org/talk/LNTS/91/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hung Bui (University of Manchester)
DTSTART:20230322T160000Z
DTEND:20230322T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/92
DESCRIPTION:Title: EG
GS\, squares and integer points on hyperelliptic curves\nby Hung Bui (
University of Manchester) as part of London number theory seminar\n\nLectu
re held in Rm. 706\, UCL Department of Mathematics (UCL Union Building).\n
\nAbstract\nErdos\, Graham and Selfridge considered\, for each positive in
teger n\, the least value of $t_n$ so that the integers $n+1\, n+2\,\\ldot
s\, n+t_n$ contain a subset the product of whose members with $n$ is a squ
are. An open problem posed by Granville concerns the size of $t_n$ under t
he assumption of the ABC Conjecture. We discuss recent work\, joint with K
yle Pratt and Alexandru Zaharescu\, in which we establish some results on
the distribution of $t_n$\, including an unconditional resolution of Granv
ille's problem.\n
LOCATION:https://researchseminars.org/talk/LNTS/92/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lassina Dembélé (King's College London)
DTSTART:20230222T160000Z
DTEND:20230222T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/93
DESCRIPTION:Title: Co
ngruences of Hilbert-Siegel modular forms and applications.\nby Lassin
a Dembélé (King's College London) as part of London number theory semina
r\n\nLecture held in Roberts Building G08\, Sir David Davies LT.\n\nAbstra
ct\nIn this talk\, we will explain how to compute congruences of Hilbert-S
iegel modular forms using compact inner forms of ${\\rm GSp}_{2g}$ given b
y unitary quaternionic groups. We will then give several applications of o
ur algorithms.\n
LOCATION:https://researchseminars.org/talk/LNTS/93/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Brian Tyrell (University of Oxford)
DTSTART:20230208T160000Z
DTEND:20230208T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/94
DESCRIPTION:Title: Fu
rther afield and further\, a field: remarks on undecidability\nby Bria
n Tyrell (University of Oxford) as part of London number theory seminar\n\
nLecture held in Rm. 706\, UCL Department of Mathematics (UCL Union Buildi
ng).\n\nAbstract\nGiven a field $K$\, one can ask "what first-order senten
ces are true in $K$"? E.g. for $K = \\mathbb{C}$\, "$\\exists x (x^2 = -1)
$" is true\, but for $K = \\mathbb{Q}$ this is false. One major area of st
udy at the intersection of logic and number theory is\, given a field $K$
of number-theoretic interest\, whether there is an algorithmic process whi
ch can decide the truth or falsity of a given first-order sentence in $K$.
For $K = \\mathbb{C}$\, there exists such an algorithmic process\; for $K
= \\mathbb{Q}$ there cannot (due to work of Gödel & Julia Robinson).\n\n
I will pose a related question: whether the logical consequences of a give
n sentence in a field may be decided algorithmically. Often the answer is
no\; so e.g. we cannot algorithmically detect general properties of fields
$K$ with a Galois extension $L$ such that $\\mathrm{Gal}(L/K) \\cong S_5$
\, or e.g. general properties of characteristic $p$ fields that admit poin
ts on a given rationally parameterisable curve over $\\mathbb{F}_p$. I wil
l focus on those fields whose behaviour is tightly controlled by their abs
olute Galois group\, and prove some precise limitations.\n\nI will aim for
this talk to be self-contained on the logic side of things!\n
LOCATION:https://researchseminars.org/talk/LNTS/94/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Félicien Comtat (Queen Mary University of London)
DTSTART:20230308T160000Z
DTEND:20230308T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/95
DESCRIPTION:Title: We
ighted vertical equidistribution of Satake parameters for GSp(4)\nby F
élicien Comtat (Queen Mary University of London) as part of London number
theory seminar\n\nLecture held in Rm. 706\, UCL Department of Mathematics
(UCL Union Building).\n\nAbstract\nThe automorphic representations of an
algebraic group G factor as a restricted tensor product of local represent
ations. In turn\, these local representations are parametrised by their Sa
take parameters. One can ask what properties the Satake parameters that do
arise from automorphic representations of G have to satisfy. For instance
\, in the verical distribution problem\, one fixes a prime p and asks for
the distribution of the Satake parameters at p of automorphic representati
ons of G varying in some families amenable to the theory of (relative) tra
ce formulae. In this talk\, I discuss the case of Maass forms on G=GSp(4).
When counted with a suitable weight coming from the Kuznetsov formula\, t
he Satake parameters equidistribute with respect to the Sato-Tate measure.
This is consistent with the generalised Ramanujan conjecture\, expected t
o hold in this situation.\n
LOCATION:https://researchseminars.org/talk/LNTS/95/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Oli Gregory (Imperial College London)
DTSTART:20230426T150000Z
DTEND:20230426T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/96
DESCRIPTION:Title: A
semistable variational p-adic Hodge conjecture\nby Oli Gregory (Imperi
al College London) as part of London number theory seminar\n\nLecture held
in KCL\, Strand Building\, Room S3.30.\n\nAbstract\nLet $k$ be a perfect
field of characteristic $p>0$\, and let $X$ be a proper scheme over $W(k)$
with semistable reduction. I shall formulate an analogue of the Fontaine-
Messing variational p-adic Hodge conjecture in this setting. To get there\
, I shall define a logarithmic version of motivic cohomology for the speci
al fibre $X_k$. This theory is related to relative log-Milnor K-theory\, l
ogarithmic Hyodo-Kato Hodge-Witt cohomology\, and log K-theory. With this
in hand\, I shall prove the deformational part of the conjecture\, simulta
neously generalising the semistable $p$-adic Lefschetz $(1\,1)$ theorem of
Yamashita (the case $r=1$) and the deformational $p$-adic Hodge conjectur
e of Bloch-Esnault-Kerz (the good reduction case). This is joint work with
Andreas Langer.\n
LOCATION:https://researchseminars.org/talk/LNTS/96/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Julia Stadlmann (University of Oxford)
DTSTART:20230503T150000Z
DTEND:20230503T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/97
DESCRIPTION:Title: Th
e mean square gap between primes\nby Julia Stadlmann (University of Ox
ford) as part of London number theory seminar\n\nLecture held in KCL\, Str
and Building\, Room S3.30.\n\nAbstract\nConditional on the Riemann hypothe
sis\, Selberg showed in 1943 that the average size of the squares of diffe
rences between consecutive primes less than $x$ is $O(log(x)^4)$. Uncondit
ional results still fall far short of this conjectured bound: Peck gave a
bound of $O(x^{0.25+\\epsilon})$ in 1996 and to date this is the best know
n bound obtained using only methods from classical analytic number theory.
\n\n\nIn this talk we discuss how sieve theory (in the form of Harman's si
eve) can be combined with classical methods to improve bounds on the numbe
r of short intervals which contain no primes\, thus improving the uncondit
ional bound on the mean square gap between primes to $O(x^{0.23+\\epsilon}
)$.\n
LOCATION:https://researchseminars.org/talk/LNTS/97/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christopher Daw (University of Reading)
DTSTART:20230510T150000Z
DTEND:20230510T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/98
DESCRIPTION:Title: La
rge Galois orbits for unlikely intersections\nby Christopher Daw (Univ
ersity of Reading) as part of London number theory seminar\n\nLecture held
in KCL\, Strand Building\, Room S3.30.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LNTS/98/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lorenzo La Porta (King's College London)
DTSTART:20230517T150000Z
DTEND:20230517T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/99
DESCRIPTION:Title: Ge
neralised theta operators\nby Lorenzo La Porta (King's College London)
as part of London number theory seminar\n\nLecture held in KCL\, Strand B
uilding\, Room S3.30.\n\nAbstract\nThe study of the classical theta operat
or was key to Edixhoven's proof of the weight part of Serre's modularity c
onjecture. Since then\, a lot of work has been devoted to extending the co
nstruction of this operator to other Shimura varieties\, with an eye towar
ds generalisations of Serre's conjecture.\nMy goal is to give an overview
of a family of generalised theta operators\, on certain unitary Shimura va
rieties\, that I constructed in my thesis and studied in subsequent work.\
n
LOCATION:https://researchseminars.org/talk/LNTS/99/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ross Paterson (University of Bristol)
DTSTART:20230524T150000Z
DTEND:20230524T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/100
DESCRIPTION:Title: Q
uadratic Twists as Random Variables\nby Ross Paterson (University of B
ristol) as part of London number theory seminar\n\nLecture held in KCL\, S
trand Building\, Room S3.30.\n\nAbstract\nIf $E/\\mathbb{Q}$ is an ellipti
c curve\, and $d$ is a squarefree integer\, then the $2$-torsion modules o
f $E$ and its quadratic twist $E_d$ are isomorphic. In particular their $2
$-Selmer groups can be made to lie in the same space. Poonen-Rains provide
a heuristic model for the behaviour of these $2$-Selmer groups individual
ly\, as E varies\, but how independent are they? We'll present results in
this direction.\n
LOCATION:https://researchseminars.org/talk/LNTS/100/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lucile Devin (Université du Littoral Côte d'Opale)
DTSTART:20230531T150000Z
DTEND:20230531T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/101
DESCRIPTION:Title: E
xceptional biases (in the distribution of irreducible polynomials over fin
ite fields)\nby Lucile Devin (Université du Littoral Côte d'Opale) a
s part of London number theory seminar\n\nLecture held in KCL\, Strand Bui
lding\, Room S3.30.\n\nAbstract\nStudying the secondary terms of the Prime
Number Theorem in Arithmetic Progressions\, Chebyshev claimed that there
are more prime numbers congruent to 3 modulo 4 than to 1 modulo 4. This cl
aim was later corrected by Littlewood\, explained\, and quantified by Rubi
nstein and Sarnak.\nPursuing the work of Cha\, we investigate analogues to
Chebyshev's bias in the setting of irreducible polynomials over finite fi
elds. In particular\, we observe exceptional behaviors occurring when the
zeros of the involved L-functions are not linearly independent. More preci
sely\, we will present instances of "complete bias" and "reversed bias"\,
and explain why they occur with probability tending to 0\, in the large q
limit.\n\nThis is joint work with Bailleul\, Keliher and Li.\n
LOCATION:https://researchseminars.org/talk/LNTS/101/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jesse Pajwani (Imperial College London)
DTSTART:20230607T150000Z
DTEND:20230607T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/102
DESCRIPTION:Title: T
he valuative section conjecture and étale homotopy\nby Jesse Pajwani
(Imperial College London) as part of London number theory seminar\n\nLectu
re held in KCL\, Strand Building\, Room S3.30.\n\nAbstract\nThe p-adic sec
tion conjecture is a long standing conjecture of Grothendieck about curves
of high genus over p-adic fields\, linking the p-adic points of a curve t
o sections of a short exact sequence of étale fundamental groups. A power
ful way of interpreting the section conjecture is as a fixed point stateme
nt\, and this interpretation makes the statement look like many other theo
rems in algebraic topology. For this talk\, we'll first introduce the fram
ing of the section conjecture as a fixed point statement\, and then show t
his interpretation allows us to give an alternate proof of part of a resul
t of Pop and Stix towards the section conjecture. This new proof generalis
es to other fields\, and the new fields allow us to extend the original re
sult to a larger class of varieties.\n
LOCATION:https://researchseminars.org/talk/LNTS/102/
END:VEVENT
BEGIN:VEVENT
SUMMARY:No talk - London-Paris Number Theory Seminar
DTSTART:20230614T150000Z
DTEND:20230614T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/103
DESCRIPTION:by No talk - London-Paris Number Theory Seminar as part of Lon
don number theory seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LNTS/103/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cathy Swaenepol (Institut de Mathématiques de Jussieu-Paris Rive
Gauche)
DTSTART:20230621T150000Z
DTEND:20230621T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/104
DESCRIPTION:Title: P
rimes and squares with preassigned digits\nby Cathy Swaenepol (Institu
t de Mathématiques de Jussieu-Paris Rive Gauche) as part of London number
theory seminar\n\nLecture held in KCL\, Strand Building\, Room S3.30.\n\n
Abstract\nBourgain (2015) estimated the number of prime numbers with a pos
itive\nproportion of preassigned digits in base 2. We first present a\nge
neralization of this result to any base $g\\geq 2$. We then discuss\na mo
re recent result for the set of squares\, which may be seen as one\nof the
most interesting sets after primes. More precisely\, for any\nbase $g\\g
eq 2$\, we obtain an asymptotic formula for the number of\nsquares with a
proportion $c>0$ of preassigned digits. Moreover we\nprovide explicit admi
ssible values for $c$ depending on $g$. Our\nproof mainly follows the str
ategy developed by Bourgain for primes in\nbase 2\, with new difficulties
for squares. It is based on the circle\nmethod and combines techniques fro
m harmonic analysis together with\narithmetic properties of squares and bo
unds for quadratic Weyl sums.\n
LOCATION:https://researchseminars.org/talk/LNTS/104/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ollie McGrath (King's College London)
DTSTART:20230628T150000Z
DTEND:20230628T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/105
DESCRIPTION:Title: T
he asymmetric additive energy of polynomials\nby Ollie McGrath (King's
College London) as part of London number theory seminar\n\nLecture held i
n KCL\, Strand Building\, Room S3.30.\n\nAbstract\nIn this talk we will se
e how sieve techniques can be used to count the number of solutions to cer
tain Diophantine equations and in particular prove that polynomials have s
mall "asymmetric additive energy."\n
LOCATION:https://researchseminars.org/talk/LNTS/105/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Otto Overkamp (Heinrich-Heine-Universität Düsseldorf)
DTSTART:20231011T150000Z
DTEND:20231011T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/106
DESCRIPTION:Title: A
proof of Chai’s conjecture\nby Otto Overkamp (Heinrich-Heine-Univer
sität Düsseldorf) as part of London number theory seminar\n\nLecture hel
d in Room 140\, the Huxley Building\, Imperial College London.\n\nAbstract
\nThe base change conductor is an invariant which measures the failure of
a semiabelian variety to have semiabelian reduction. It was conjectured by
Chai that this invariant is additive in certain exact sequences. I shall
report on recent joint work with Takashi Suzuki which implies this conject
ure. Time permitting\, I shall also discuss counterexamples to a generalis
ation of Chai’s conjecture.\n
LOCATION:https://researchseminars.org/talk/LNTS/106/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Julian Demeio (Bath)
DTSTART:20231018T150000Z
DTEND:20231018T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/107
DESCRIPTION:Title: H
ilbert Property for Hilbert modular surfaces\nby Julian Demeio (Bath)
as part of London number theory seminar\n\nLecture held in Room 140\, the
Huxley Building\, Imperial College London.\n\nAbstract\nWork in progress w
ith Damián Gvirtz. We prove the Hilbert Property for several Hilbert modu
lar surfaces. Some of these are K3s\, and the elliptic fibration method is
employed. As an application\, we obtain a positive answer to the inverse
Galois problem in some new cases: namely for $PSL_2(F_{p^2})$ for $p$ lyin
g in a union of several arithmetic sequences.\n
LOCATION:https://researchseminars.org/talk/LNTS/107/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Amina Abdurrahman (IHES)
DTSTART:20231115T160000Z
DTEND:20231115T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/108
DESCRIPTION:Title: S
quare roots of symplectic L-functions and Reidemeister torsion\nby Ami
na Abdurrahman (IHES) as part of London number theory seminar\n\nLecture h
eld in Room 140\, the Huxley Building\, Imperial College London.\n\nAbstra
ct\nWe give a purely topological formula for the square class of the centr
al value of the L-function of a symplectic representation on a curve. We a
lso formulate a topological analogue of the statement\, in which the centr
al value of the L-function is replaced by Reidemeister torsion of 3-manifo
lds. This is related to the theory of epsilon factors in number theory and
Meyer's signature formula in topology among other topics. We will present
some of these ideas and sketch aspects of the proof. This is joint work w
ith Akshay Venkatesh.\n
LOCATION:https://researchseminars.org/talk/LNTS/108/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco D’Addezio (Jussieu)
DTSTART:20231122T160000Z
DTEND:20231122T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/109
DESCRIPTION:Title: T
he p-torsion of the Brauer group of an abelian variety\nby Marco D’A
ddezio (Jussieu) as part of London number theory seminar\n\nLecture held i
n Room 140\, the Huxley Building\, Imperial College London.\n\nAbstract\nI
will present a new finiteness result for the $p$-primary torsion of the t
ranscendental Brauer group of abelian varieties in characteristic $p$. Thi
s follows from a certain “fppf variant” of the Tate conjecture for abe
lian varieties. The main ingredient in the proof is de Jong's crystalline
Tate conjecture. In the talk\, I will recall de Jong's theorem\, the relat
ion between crystalline cohomology and the fppf cohomology of $\\mu_p^n$\,
and I will explain some steps of the proof.\n
LOCATION:https://researchseminars.org/talk/LNTS/109/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yujie Xu (Columbia)
DTSTART:20231129T160000Z
DTEND:20231129T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/110
DESCRIPTION:Title: H
ecke algebras for p-adic groups and explicit Local Langlands Correspondenc
e\nby Yujie Xu (Columbia) as part of London number theory seminar\n\nL
ecture held in Room 140\, the Huxley Building\, Imperial College London.\n
\nAbstract\nI will talk about several results on Hecke algebras attached t
o Bernstein blocks of (arbitrary) reductive p-adic groups\, where we const
ruct a local Langlands correspondence for these Bernstein blocks. Our tech
niques draw inspirations from the foundational works of Deligne\, Kazhdan
and Lusztig. \n\nAs an application\, we prove the (classical) Local Langla
nds Conjecture for G_2\, which is the first known case in literature of (c
lassical) LLC for exceptional groups. Our correspondence satisfies an expe
cted property on cuspidal support\, which is compatible with the generaliz
ed Springer correspondence (for Lusztig's perverse sheaves)\, along with a
list of characterizing properties including the stabilization of characte
r sums. In particular\, we obtain "mixed" L-packets containing "F-singular
" supercuspidals and non-supercuspidals. Such "mixed" L-packets had been e
lusive up until this point and very little was known prior to our work. I
will give explicit examples of such mixed L-packets using Deligne-Lusztig
theory and Kazhdan-Lusztig parametrization. \n\nIf time permits\, I will e
xplain how to pin down certain choices in the construction of the correspo
ndence using stability of L-packets\; one key input is a homogeneity resul
t due to Waldspurger and DeBacker. Moreover\, I will mention how to adapt
our general strategy to construct explicit LLC for other reductive groups\
, such as GSp(4)\, Sp(4)\, etc. Such explicit description of the L-packets
(e.g. the Kazhdan-Lusztig parameters) has been useful in applications to
modularity lifting questions as in the recent work of Whitmore. \n\nSome p
arts of this talk are based on my joint work with Aubert\, and some other
parts are based on my joint work with Suzuki.\n
LOCATION:https://researchseminars.org/talk/LNTS/110/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pol van Hoften (VU Amsterdam)
DTSTART:20231206T160000Z
DTEND:20231206T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/111
DESCRIPTION:Title: O
n Exotic Hecke correspondences\nby Pol van Hoften (VU Amsterdam) as pa
rt of London number theory seminar\n\nLecture held in Room 140\, the Huxle
y Building\, Imperial College London.\n\nAbstract\nThe goal of this talk i
s to explain joint work in progress with Jack Sempliner on the constructio
n of "exotic" Hecke correspondences between the mod p fibers of different
Shimura varieties of Hodge type. Our work generalizes forthcoming work of
Xiao-Zhu\; our results cover the new situation where the groups underlying
the two different Shimura varieties are allowed to be to be non-isomorphi
c at p. As a consequence of our main results\, we obtain exotic isomorphis
ms of Igusa varieties in the style of Caraiani-Tamiozzo. In the talk\, I w
ill give many illustrative examples.\n
LOCATION:https://researchseminars.org/talk/LNTS/111/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emiliano Ambrosi (Strasbourg)
DTSTART:20231213T160000Z
DTEND:20231213T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/112
DESCRIPTION:Title: R
eduction modulo p of the Noether problem\nby Emiliano Ambrosi (Strasbo
urg) as part of London number theory seminar\n\nLecture held in Room 140\,
the Huxley Building\, Imperial College London.\n\nAbstract\nLet k be an a
lgebraically closed field of characteristic p≥0 and V a faithful k-ratio
nal representation of an l-group G. The Noether's problem asks whether V/G
is (stably) birational to a point. If l is equal to p\, then Kuniyoshi pr
oved that this is true\, while\, if l is different from p\, Saltman constr
ucted l-groups for which V/G is not stably rational. Hence\, the geometry
of V/G depends heavily on the characteristic of the field. We show that
for all the groups G constructed by Saltman\, one cannot interpolate betwe
en the Noether problem in characteristic 0 and p. More precisely\, we show
that it does not exist a complete valuation ring R of mixed characteristi
c (0\,p) and a smooth proper R-scheme X---->Spec(R) whose special fiber an
d generic fiber are both stably birational to V/G. The proof combines the
integral p-adic Hodge theoretic results of Bhatt-Morrow-Scholze\, with the
study of the Cartier operator on differential forms in positive character
istic. This is a joint work with Domenico Valloni.\n
LOCATION:https://researchseminars.org/talk/LNTS/112/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Wataru Kai (Tohoku University)
DTSTART:20231108T160000Z
DTEND:20231108T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/113
DESCRIPTION:Title: L
inear patterns of prime elements in number fields\nby Wataru Kai (Toho
ku University) as part of London number theory seminar\n\nLecture held in
Room 140\, the Huxley Building\, Imperial College London.\n\nAbstract\nI w
ill discuss my recent result that gives a sufficient condition for a set o
f finitely many polynomials of degree 1 with coefficients in a number ring
to attain simultaneous prime values. This extends a 2012 theorem of Green
-Tao-Ziegler from the case of Z to the general case. Time permitting\, I w
ill mention how this can be applied to produce (modestly) new families of
varieties over number fields which satisfy the Hasse principle for rationa
l points by using the so-called fibration methods.\n
LOCATION:https://researchseminars.org/talk/LNTS/113/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ambrus Pal (Imperial)
DTSTART:20231025T150000Z
DTEND:20231025T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/114
DESCRIPTION:Title: T
ate's conjecture for certain Drinfeld modular surfaces\nby Ambrus Pal
(Imperial) as part of London number theory seminar\n\nLecture held in Room
140\, the Huxley Building\, Imperial College London.\n\nAbstract\nTate's
conjecture on algebraic cycles is one of the central conjectures in arithm
etic geometry\, but it is open even for codimension one cycles. There are
only a few classes of varieties when this claim is known. I will report ab
out a new class of surfaces defined over global function fields which were
defined by Stuhler in there original form\, and are closely analogous to
Hilbert modular surfaces. Our proof employs p-adic methods\, including the
p-adic Lefschetz (1\,1) theorem proved by Lazda and myself. We also explo
it that these varieties are totally degenerate in the sense of Raskind\, b
ut this is not sufficient\, we need some information from the Langlands co
rrespondence\, too. I will also talk about some particularly simple surfac
es which show that the first property cannot be used to give a quicker pro
of. Joint work with Koskivirta.\n
LOCATION:https://researchseminars.org/talk/LNTS/114/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bence Hevesi (Imperial)
DTSTART:20231101T160000Z
DTEND:20231101T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/115
DESCRIPTION:Title: L
ocal-global compatibility at l=p for torsion automorphic Galois representa
tions\nby Bence Hevesi (Imperial) as part of London number theory semi
nar\n\nLecture held in Room 140\, the Huxley Building\, Imperial College L
ondon.\n\nAbstract\nSome 10 years ago\, Scholze proved the existence of Ga
lois representations associated with torsion classes appearing in the coho
mology of locally symmetric spaces for GL_n over imaginary CM fields. Sinc
e then\, the question of local-global compatibility for his automorphic Ga
lois representations has been an active area of research. I will report on
my work on verifying a rather general local-global compatibility at l=p i
n this direction\, generalising the already existing results of the celebr
ated 10 author paper and Caraiani—Newton.\n
LOCATION:https://researchseminars.org/talk/LNTS/115/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matthew Honnor (Imperial)
DTSTART:20240110T160000Z
DTEND:20240110T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/116
DESCRIPTION:Title: R
efined conjectures of Birch and Swinnerton-Dyer type\nby Matthew Honno
r (Imperial) as part of London number theory seminar\n\nLecture held in Ch
adwick G07 (UCL).\n\nAbstract\nIn analogy to Stickelberger's Theorem and r
efining the Birch—Swinnerton-Dyer Conjecture\, Mazur—Tate conjecture a
n order of vanishing and main conjecture for a certain group ring element.
This element is defined in terms of modular symbols and relates to the t
wisted Hasse—Weil $L$-series of elliptic curves. In this talk I will exp
lain the conjectures of Mazur—Tate and report on work in progress\, join
t with Dominik Bullach\, in which we prove new results towards these conje
ctures.\n
LOCATION:https://researchseminars.org/talk/LNTS/116/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dominik Bullach (UCL)
DTSTART:20240117T160000Z
DTEND:20240117T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/117
DESCRIPTION:Title: O
n some recent developments in the theory of Euler systems\nby Dominik
Bullach (UCL) as part of London number theory seminar\n\nLecture held in G
02 Watson LT\, Medawar Building.\n\nAbstract\nEver since their introductio
n\, Euler systems have played an important role in \nproving conjectures o
n leading terms of L-series such as instances of the Tamagawa \nNumber Con
jecture of Bloch and Kato. In this talk\, I will survey some recent develo
pments \nin the general theory of Euler systems\, including joint work in
progress with David Burns.\n
LOCATION:https://researchseminars.org/talk/LNTS/117/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Netan Dogra (KCL)
DTSTART:20240124T160000Z
DTEND:20240124T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/118
DESCRIPTION:Title: O
n the Zilber-Pink conjecture for a product of curves\nby Netan Dogra (
KCL) as part of London number theory seminar\n\nLecture held in Executive
Suite 103\, Engineering Front Building.\n\nAbstract\nLet $X$ be a curve of
genus $g>1$ over the complex numbers. What is the Zariski closure\, insid
e $X^n$\, of the set of $n$-tuples of points $(z_i)$ for which there exist
s a non-constant function $f$ on $X$ with divisor supported on $\\{z_i\\}$
? This question can be viewed as a special case of the Zilber-Pink conject
ure\, which is a broad generalisation of the Andre-Oort conjecture. In thi
s talk I will describe new results which answer this question for some $(X
\,n)$. This is joint work with Arnab Saha (IIT Gandhinagar).\n
LOCATION:https://researchseminars.org/talk/LNTS/118/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ju-Feng Wu (University of Warwick)
DTSTART:20240131T160000Z
DTEND:20240131T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/119
DESCRIPTION:Title: O
verconvergent Eichler—Shimura morphisms for Siegel modular forms\nby
Ju-Feng Wu (University of Warwick) as part of London number theory semina
r\n\nLecture held in 9 Garwood LT\, South Wing.\n\nAbstract\nA theorem of
Faltings—Chai provides a comparison between the étale cohomology of the
Siegel modular variety and the coherent cohomology of automorphic sheaves
\, which generalises the classical Eichler—Shimura decomposition in the
case of modular forms. In this talk\, based on joint work with Hansheng Di
ao and Giovanni Rosso\, I will discuss how to $p$-adically interpolate the
result of Faltings—Chai. The strategy is inspired by the work of Chojec
ki—Hansen—Johansson\; one of the key ingredients is Higher Coleman The
ory\, recently introduced by Boxer—Pilloni.\n
LOCATION:https://researchseminars.org/talk/LNTS/119/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cecilia Busuioc (UCL)
DTSTART:20240207T160000Z
DTEND:20240207T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/120
DESCRIPTION:Title: M
odular symbols with values in Beilinson-Kato distributions\nby Cecilia
Busuioc (UCL) as part of London number theory seminar\n\nLecture held in
Executive Suite 103\, Engineering Front Building.\n\nAbstract\nIn this tal
k\, we will describe the construction of a $\\operatorname{GL}_n(\\mathbb{
Q})$-invariant modular symbol with coefficients in a space of distribution
s that take values in Milnor K-groups of modular function fields. This is
based on joint work with J. Park\, O. Patashnick and G. Stevens.\n
LOCATION:https://researchseminars.org/talk/LNTS/120/
END:VEVENT
BEGIN:VEVENT
SUMMARY:James Newton (Oxford)
DTSTART:20240221T160000Z
DTEND:20240221T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/121
DESCRIPTION:Title: B
ase change for modular forms\nby James Newton (Oxford) as part of Lond
on number theory seminar\n\nLecture held in Executive Suite 103\, Engineer
ing Front Building.\n\nAbstract\nI'll talk about the base change lifting f
rom holomorphic modular forms to Hilbert modular forms for totally real fi
elds F. A new proof of the existence of this base change lifting is contai
ned in joint work with Laurent Clozel and Jack Thorne. \n\nThe base change
lifting is a simple example of Langlands functoriality\, corresponding on
the Galois side to restriction to the absolute Galois group of F. When F
is a solvable extension of Q\, its existence was proved by Langlands using
the twisted trace formula (earlier work by Doi and Naganuma covered the c
ase where F is quadratic). Dieulefait used modularity lifting theorems and
a delicate construction of chains of congruences between modular forms to
prove the existence of the base change lifting without a solvability assu
mption. Our new proof replaces (at least some of) this chain of congruence
s with a `p-adic analytic continuation of functoriality' step\, adapted fr
om my work with Thorne on symmetric power functoriality.\n
LOCATION:https://researchseminars.org/talk/LNTS/121/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Asbjørn Nordentoft (Université Paris-Saclay)
DTSTART:20240228T160000Z
DTEND:20240228T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/122
DESCRIPTION:Title: H
orizontal p-adic L-functions\nby Asbjørn Nordentoft (Université Pari
s-Saclay) as part of London number theory seminar\n\nLecture held in A1/3\
, Physics Building.\n\nAbstract\nGoldfeld’s Conjecture predicts that exa
ctly 50% of quadratic twists of a fixed elliptic curve will have L-functio
n vanishing at the central point. When considering the non-vanishing of tw
ists of elliptic curve L-functions by characters of (fixed) order greater
than 2\, it has been predicted by David-Fearnly-Kisilevsky that 100% shoul
d be non-vanishing. Very little was previously known outside the quadratic
case as the problem lies beyond the current technology of e.g. analytic n
umber theory. In this talk I will present a p-adic approach relying on the
construction of a ‘horizontal p-adic L-function’. This approach yield
s strong quantitative non-vanishing results for general order twists. In p
articular\, we obtain the best bound towards Goldfeld's Conjecture for one
hundred percent of elliptic curves (improving on a result of Ono).\n\nThi
s is joint work with Daniel Kriz.\n
LOCATION:https://researchseminars.org/talk/LNTS/122/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Shaun Stevens (University of East Anglia)
DTSTART:20240306T160000Z
DTEND:20240306T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/123
DESCRIPTION:Title: H
ow many local factors does it take to determine a representation?\nby
Shaun Stevens (University of East Anglia) as part of London number theory
seminar\n\nLecture held in Medawar G02 Watson.\n\nAbstract\nIn 1993\, Henn
iart proved that the (then conjectural) Local Langlands Correspondence for
$\\operatorname{GL}(n$) is determined by gamma-factors of pairs. More pre
cisely\, he proved a local converse theorem: for $F$ a non-archimedean loc
al field\, an irreducible (smooth complex) representation $\\pi$ of $\\ope
ratorname{GL}(n\,F)$ is determined by the collection of gamma-factors of t
he pairs $(\\pi\,\\tau)$ as $\\tau$ runs through the irreducible represent
ations of all $\\operatorname{GL}(m\,F)$ with $m < n$. More recently\, Cha
i (2019) and Jacquet—Liu (2018) showed that one only needs to consider $
m\\leq n/2$ to determine $\\pi$. This bound on $m$ is best possible\, at l
east when $n$ is less that the residual characteristic of $F$\, by work of
Adrian—Liu—Stevens—Tam (2018) and Adrian (2023). \n\n \n\nFor group
s other than $\\operatorname{GL}(n)$ there are additional complications. I
’ll explain what I know is already known about this problem and report o
n some joint work with Moshe Adrian\, which gives some answers but also le
aves many questions.\n
LOCATION:https://researchseminars.org/talk/LNTS/123/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tom Fisher (Cambridge)
DTSTART:20240313T160000Z
DTEND:20240313T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/124
DESCRIPTION:Title: C
omputing the Cassels-Tate pairing on the 2-Selmer group of a genus 2 Jacob
ian\nby Tom Fisher (Cambridge) as part of London number theory seminar
\n\nLecture held in Medawar G02 Watson.\n\nAbstract\nIn her 2021 thesis\,
my student Jiali Yan gave a practical method\nfor computing the Cassels-Ta
te pairing on the 2-Selmer group of the\nJacobian of a genus 2 curve all o
f whose Weierstrass points are rational.\nShe also gave a second method wi
thout any assumption on the Weierstrass\npoints\, but instead assuming we
can find a rational point on a certain\ntwisted Kummer surface. The two me
thods can be thought of as generalising\nmethods of Cassels and Donnelly i
n the elliptic curve case. I will\ndescribe a practical refinement of the
second method which is now\nimplemented in Magma\, and has been used to un
conditionally determine the\nranks of all genus 2 Jacobians in the LMFDB.\
n
LOCATION:https://researchseminars.org/talk/LNTS/124/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simon Wadsley
DTSTART:20240320T160000Z
DTEND:20240320T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/125
DESCRIPTION:Title: E
quivariant vector bundles with connection on the p-adic half-plane\nby
Simon Wadsley as part of London number theory seminar\n\nLecture held in
Watson Lecture Theatre G02\, Medawar Building.\n\nAbstract\nRecent joint w
ork with Konstantin Ardakov has been devoted\nto classifying equivariant l
ine bundles with flat connection on the\nDrinfeld $p$-adic half-plane defi
ned over $F$\, a finite extension of $\\mathbb{Q}_p$\,\nand proving that t
heir global sections yield admissible locally\nanalytic representations of
$\\operatorname{GL}_2(F)$ of finite length. In this talk we\nwill discuss
this work and invite reflection on how it might be\nextended to equivaria
nt vector bundles with connection on the $p$-adic\nhalf-plane.\n
LOCATION:https://researchseminars.org/talk/LNTS/125/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Manuel Hauke (University of York)
DTSTART:20240501T150000Z
DTEND:20240501T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/126
DESCRIPTION:Title: D
uffin-Schaeffer meets Littlewood and related topics\nby Manuel Hauke (
University of York) as part of London number theory seminar\n\nLecture hel
d in Room K0.18 King's Building\, King's College London (Strand Campus).\n
\nAbstract\nKhintchine's Theorem is one of the cornerstones in metric Diop
hantine approximation. The question of removing the monotonicity condition
on the approximation function in Khintchine's Theorem led to the recently
proved Duffin-Schaeffer conjecture. Gallagher showed an analogue of Khint
chine's Theorem for multiplicative Diophantine approximation\, again assum
ing monotonicity. \n \n In this talk\, I will discuss my joint work with L
. Frühwirth about a Duffin-Schaeffer version for Gallagher's Theorem. Fur
thermore\, I will give a broader overview on various questions in metric D
iophantine approximation and demonstrate the deep connection to analytic n
umber theory that lies in the heart of the corresponding proofs.\n
LOCATION:https://researchseminars.org/talk/LNTS/126/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Efthymios Sofos (University of Glasgow)
DTSTART:20240508T150000Z
DTEND:20240508T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/127
DESCRIPTION:Title: 6
-torsion and integral points on quartic surfaces\nby Efthymios Sofos (
University of Glasgow) as part of London number theory seminar\n\nLecture
held in Room K0.18 King's Building\, King's College London (Strand Campus)
.\n\nAbstract\nI will discuss some new results on averages of multiplicati
ve functions over integer sequences. We will then give applications to Coh
en-Lenstra and Manin's conjecture. Joint work with Chan\, Koymans and Paga
no.\n
LOCATION:https://researchseminars.org/talk/LNTS/127/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lewis Combes (University of Sheffield)
DTSTART:20240515T150000Z
DTEND:20240515T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/128
DESCRIPTION:Title: P
eriod polynomials of Bianchi modular forms\nby Lewis Combes (Universit
y of Sheffield) as part of London number theory seminar\n\nLecture held in
Room K0.18 King's Building\, King's College London (Strand Campus).\n\nAb
stract\nBianchi modular forms (i.e. automorphic forms over imaginary quadr
atic fields) share many similarities with their classical cousins. One suc
h similarity is the period polynomial\, studied for classical modular form
s by Manin\, Kohnen and Zagier\, as well as many others. In this talk we d
efine period polynomials of Bianchi modular forms\, show how to compute th
em in practice\, and use them to (conjecturally) extract information about
congruences between Bianchi forms of various types (base-change and genui
ne forms\; cusp forms and Eisenstein series). All of this is done through
an example space of Bianchi forms\, from which we find new congruences mod
ulo 43 and 173. Time permitting\, we will also describe some open problems
relating to these methods\, and how these relate to the classical picture
. No prior knowledge of Bianchi modular forms is assumed.\n
LOCATION:https://researchseminars.org/talk/LNTS/128/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ofir Gorodetsky (University of Oxford)
DTSTART:20240529T150000Z
DTEND:20240529T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/129
DESCRIPTION:Title: M
artingale central limit theorems for weighted sums of random multiplicativ
e functions\nby Ofir Gorodetsky (University of Oxford) as part of Lond
on number theory seminar\n\nLecture held in Room K0.18 King's Building\, K
ing's College London (Strand Campus).\n\nAbstract\nA random multiplicative
function is a multiplicative function alpha(n) such that its values on pr
imes\, (alpha(p))_(p=2\,3\,5\,...)\, are i.i.d. random variables. The simp
lest example is the Steinhaus function\, which is a completely multiplicat
ive function with alpha(p) uniformly distributed on the unit circle. A bas
ic question in the field is finding the limiting distribution of the (norm
alized) sum of alpha(n) from n=1 to n=x\, possibly restricted to a subset
of integers of interest. This question is currently resolved only in a few
cases. We shall describe ongoing work where we are able to find the limit
ing distribution in many new instances of interest. The distribution we fi
nd is not gaussian\, in contrast to all previous works. This is joint work
with Mo Dick Wong (Durham University).\n
LOCATION:https://researchseminars.org/talk/LNTS/129/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vandita Patel (University of Manchester)
DTSTART:20240619T150000Z
DTEND:20240619T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/130
DESCRIPTION:Title: V
alues of the Ramanujan tau-function\nby Vandita Patel (University of M
anchester) as part of London number theory seminar\n\nLecture held in KCL
K0.18.\n\nAbstract\nThe infamous Ramanujan tau-function is the starting po
int for many mysterious conjectures and difficult open problems within the
realm of modular forms. In this talk\, I will discuss some of our recent
results pertaining to odd values of the Ramanujan tau-function. We use a c
ombination of tools which include the Primitive Divisor Theorem of Bilu\,
Hanrot and Voutier\, bounds for solutions to Thue–Mahler equations due t
o Bugeaud and Gyory\, and the modular approach via Galois representations
of Frey-Hellegouarch elliptic curves. This is joint work with Mike Bennett
(UBC)\, Adela Gherga (Warwick) and Samir Siksek (Warwick)\n
LOCATION:https://researchseminars.org/talk/LNTS/130/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mohamed Tawfik (King's College London)
DTSTART:20240424T150000Z
DTEND:20240424T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/131
DESCRIPTION:Title: B
rauer-Manin obstructions for Kummer surfaces\nby Mohamed Tawfik (King'
s College London) as part of London number theory seminar\n\nLecture held
in K0.18\, King's Building\, Strand Campus\, King's College London.\n\nAbs
tract\nWe start by introducing Brauer-Manin obstructions to local-global p
rinciples over varieties. We then move to some of the known literature on
Brauer-Manin obstructions for Kummer surfaces of products of elliptic curv
es. We finally present our work on some of the special cases where we calc
ulate the Brauer group of a Kummer surface $X=Kum(E \\times E')$ of a prod
uct of CM elliptic curves $E$ and $E'$\, where $End(E)=End(E')=\\mathbb{Z}
[\\zeta_3]$\, and show that a non-trivial 5-torsion element of the transce
ndental Brauer group gives rise to Brauer Manin obstruction to weak approx
imation for $X$.\n
LOCATION:https://researchseminars.org/talk/LNTS/131/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lazar Radicevic (King's College London)
DTSTART:20240522T150000Z
DTEND:20240522T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/132
DESCRIPTION:Title: P
rojective geometry and invariant theory of elliptic curves and rings of fi
nite rank\nby Lazar Radicevic (King's College London) as part of Londo
n number theory seminar\n\nLecture held in K0.18\, King's Building\, Stran
d Campus\, King's College London.\n\nAbstract\nI will explain how free res
olutions of ideals can be used to systematically formulate invariant theor
y for several moduli spaces of varieties that are of interest in arithmeti
c statistics and computational number theory. In particular\, we extend th
e classical invariant theory formulas for the Jacobian of a genus one curv
e of degree n=2\,3\,4\,5 to curves of arbitrary degree\, generalizing the
work on genus one models of Cremona\, Fisher and Stoll\, and in a joint w
ork with Tom Fisher\, we compute structure constants for a rank n ring fro
m the free resolution of its associated set of n points in projective spac
e\, generalizing the previously known constructions of Levi-Delone-Faddeev
and Bhargava. Time permitting I will talk about an ongoing project to ext
end these results to abelian varieties of higher dimension.\n
LOCATION:https://researchseminars.org/talk/LNTS/132/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jean-Baptiste Teyssier (Université Sorbonne)
DTSTART:20240605T150000Z
DTEND:20240605T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/133
DESCRIPTION:Title: B
oundedness for Betti numbers of étale sheaves in positive characteristic.
\nby Jean-Baptiste Teyssier (Université Sorbonne) as part of London n
umber theory seminar\n\nLecture held in K0.18\, King's Building\, Strand C
ampus\, King's College London.\n\nAbstract\nCohomology is the most fundame
ntal global invariant attached to a sheaf. For a \\bar{Q}_l local system L
on the complement of a divisor D in a smooth projective variety over an a
lgebraically closed field of characteristic p ≠ l\, we will advertise th
e existence of estimates for the rank of each cohomology spaces of L depen
ding only on local data : the rank of L and the ramification conductors of
L at the generic points of D. This is joint work with Haoyu Hu.\n
LOCATION:https://researchseminars.org/talk/LNTS/133/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sylvy Anscombe (Université Paris Cité)
DTSTART:20240612T150000Z
DTEND:20240612T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/134
DESCRIPTION:Title: U
niform aspects of the theory of complete valued fields\nby Sylvy Ansco
mbe (Université Paris Cité) as part of London number theory seminar\n\nL
ecture held in K0.18\, King's Building\, Strand Campus\, King's College Lo
ndon.\n\nAbstract\nA good deal of the arithmetic of a field can be express
ed by sentences in the first-order language of rings. The theories\nof the
characteristic zero local fields have been axiomatized and are decidable:
in the case of $Q_p$ and its finite extensions\,\nAx\, Kochen\, and (inde
pendently) Ershov\, gave complete axiomatizations that are centred on a fo
rmalization of Hensel’s\nLemma. In fact the theory of any field of chara
cteristic zero which is complete with respect to a non-archimedean\nvaluat
ion can be likewise axiomatized.\n\nI will explain recent joint work with
Jahnke\, and also with Dittmann and Jahnke\, in which we extend the classi
cal\nwork on these theories to include the case of imperfect residue field
s. In particular we show that “Hilbert’s Tenth\nProblem” (H10) in th
ese fields (i.e. the problem of effectively determining whether a given Di
ophantine equation has\nsolutions) is solvable if and only if the analogou
s problem is solvable on a structure we define on the residue field. This\
nfollows a pattern of such “transfer” results for H10 — established
for valued fields of positive characteristic in earlier\nwork with Fehm
— although in the current case we really need the extra structure.\n\nI
will describe these results\, focusing on the extent to which they depend
(or not) on the residue field. If there is\ntime I will discuss the aforem
entioned H10 transfer for complete valued fields in positive characteristi
c\, including more\nrecent uniform aspects.\n\nI will not assume a backgro
und in logic.\n
LOCATION:https://researchseminars.org/talk/LNTS/134/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ana Caraiani (Imperial College London)
DTSTART:20240626T150000Z
DTEND:20240626T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/135
DESCRIPTION:Title: T
owards an Eichler-Shimura decomposition for ordinary p-adic Siegel modular
forms\nby Ana Caraiani (Imperial College London) as part of London nu
mber theory seminar\n\nLecture held in K0.18\, King's Building\, Strand Ca
mpus\, King's College London.\n\nAbstract\nThere are two different ways to
construct families of ordinary p-adic Siegel modular forms. One is by p-a
dically interpolating classes in Betti cohomology\, first introduced by Hi
da and then given a more representation-theoretic interpretation by Emerto
n. The other is by p-adically interpolating classes in coherent cohomology
\, once again pioneered by Hida and generalised in recent years by Boxer a
nd Pilloni. I will explain these two constructions and then discuss joint
work in progress with James Newton and Juan Esteban Rodríguez Camargo tha
t aims to compare them.\n
LOCATION:https://researchseminars.org/talk/LNTS/135/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christopher Skinner (Princeton University)
DTSTART:20240605T120000Z
DTEND:20240605T130000Z
DTSTAMP:20260315T025337Z
UID:LNTS/136
DESCRIPTION:Title: A
nticyclotomic Euler systems for Conjugate-dual Galois representations\
nby Christopher Skinner (Princeton University) as part of London number th
eory seminar\n\nLecture held in K0.18\, King's Building\, Strand Campus\,
King's College London.\n\nAbstract\nI will explain a definition of Euler s
ystems for anticyclotomic extensions of a CM extension K/F. This allows on
e to prove analogs of Kolyvagin's famous results for Heegner points (rank
one\, finiteness of Tate-Shafarevich groups) for a very general class of G
alois representations over CM fields. A novel feature of this approach is
to focus on primes that split in K/F (as opposed to Kolyvagin's inert prim
es). I will also describe some of the many examples of such Euler systems
that have been constructed recently. This is joint work with Dimitar Jetc
hev and was begun in collaboration with Jan Nekovar.\n
LOCATION:https://researchseminars.org/talk/LNTS/136/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carl Wang-Erickson (University of Pittsburgh)
DTSTART:20240605T133000Z
DTEND:20240605T143000Z
DTSTAMP:20260315T025337Z
UID:LNTS/137
DESCRIPTION:Title: C
ritical Hida theory\, bi-ordinary complexes\, and weight 1 coherent cohomo
logy\nby Carl Wang-Erickson (University of Pittsburgh) as part of Lond
on number theory seminar\n\nLecture held in K0.18\, King's Building\, Stra
nd Campus\, King's College London.\n\nAbstract\nColeman made observations
about overconvergent modular forms of weight at least 2 and critical slope
which imply that they are almost spanned by two subspaces corresponding t
o two different kinds of twist of ordinary overconvergent modular forms. H
e also showed that the “almost” is accounted for by a square-nilpotent
action of Hecke operators. Motivated by questions about Galois representa
tions associated to these forms\, we intersect these two twists to define
“bi-ordinary” forms. But we do this in a derived way: the sum operatio
n from the two twisted ordinary subspaces to the space of critical forms d
efines a length 1 “bi-ordinary complex\," making the bi-ordinary forms t
he 0th degree of bi-ordinary cohomology and realizing the square-nilpotent
Hecke action as a degree-shifting action. Relying on classical Hida theor
y as well as the higher Hida theory of Boxer-Pilloni\, we interpolate this
complex over weights. We can deduce “R=T” theorems in the critical an
d bi-ordinary cases from R=T theorems in the ordinary case. And specializi
ng to weight 1 under a supplemental assumption\, we show that the bi-ordin
ary complex with its square-nilpotent Hecke action specializes to weight 1
coherent cohomology of the modular curve with a degree-shifting action of
a Stark unit group. The action is a candidate for a p-adic realization of
conjectures about motivic actions of Venkatesh\, Harris\, and Prasanna. T
his is joint work with Francesc Castella.\n
LOCATION:https://researchseminars.org/talk/LNTS/137/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kalyani Kansal (Imperial)
DTSTART:20241009T150000Z
DTEND:20241009T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/138
DESCRIPTION:Title: N
on-generic components of the Emerton-Gee stack for GL$_2$\nby Kalyani
Kansal (Imperial) as part of London number theory seminar\n\nLecture held
in Huxley 140\, Imperial College.\n\nAbstract\nLet $K$ be an unramified ex
tension of $\\mathbb{Q}_p$ for a prime p > 3. The reduced part of the Emer
ton-Gee stack for $\\mathrm{GL}_2$ can be viewed as parameterizing two-dim
ensional mod p Galois representations of the absolute Galois group of $K$.
In this talk\, we will consider the extremely non-generic irreducible com
ponents of this reduced part and see precisely which ones are smooth or no
rmal\, and which have Gorenstein or Cohen-Macaulay normalizations\, as wel
l as determine their singular loci. We will see some consequences of this
study for the conjectural categorical p-adic Langlands correspondence. Thi
s is based on recent joint work with Ben Savoie.\n
LOCATION:https://researchseminars.org/talk/LNTS/138/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Martin Ortiz (Imperial)
DTSTART:20241016T150000Z
DTEND:20241016T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/139
DESCRIPTION:Title: T
heta linkage maps and the weight part of Serre's conjecture\nby Martin
Ortiz (Imperial) as part of London number theory seminar\n\nLecture held
in Huxley 140\, Imperial College.\n\nAbstract\nThe weight part of Serre's
conjecture seeks to understand mod p congruences of automorphic forms of d
ifferent weights. For modular forms a key ingredient in its proof was Edix
hoven's use of the theta operator on the modular curve. I will explain the
construction of a new family of theta operators on Shimura varieties\, an
d how they are related to the conjectures of Herzig on the weight part of
Serre's conjecture. As an application I prove a generic entailment for the
group GSp4\, i.e. a Hecke eigenform for a generic Serre weight in the low
est alcove is also modular for a Serre weight in one of the upper alcoves.
\n
LOCATION:https://researchseminars.org/talk/LNTS/139/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Seoyoung Kim (University of Göttingen)
DTSTART:20241023T150000Z
DTEND:20241023T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/140
DESCRIPTION:Title: C
ertain families of K3 surfaces and their modularity\nby Seoyoung Kim (
University of Göttingen) as part of London number theory seminar\n\nLectu
re held in Huxley 140\, Imperial College.\n\nAbstract\nWe start with a dou
ble sextic family of K3 surfaces with four parameters with Picard number $
16$. Then by geometric reduction (top-to-bottom) processes\, we obtain thr
ee\, two and one parameter families of K3 surfaces of Picard number $17\,
18$ and $19$ respectively. All these families turn out to be of hypergeome
tric type in the sense that their Picard--Fuchs differential equations are
given by hypergeometric or Heun functions. We will study the geometry of
two parameter families in detail.\n\nWe will then prove\, after suitable s
pecializations of parameters\, these K3 surfaces will have CM (complex mu
ltiplication)\, and will become modular in the sense that the Galois repre
sentations of dimensions $\\leq 6$ associated to the transcendental lattic
es are all induced from $1$-dimensional representations. Thus\, these K3 s
urfaces will be determined by modular forms of various weights. This is do
ne starting with one-parameter family establishing the modularity at speci
al fibers\, and then applying arithmetic induction (bottom-to-top) process
es to multi-parameter families. This is a joint work with A. Clingher\, A.
Malmendier\, and N. Yui.\n
LOCATION:https://researchseminars.org/talk/LNTS/140/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Florian Breuer (University of Newcastle)
DTSTART:20241030T160000Z
DTEND:20241030T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/141
DESCRIPTION:Title: C
oefficients of modular polynomials\nby Florian Breuer (University of N
ewcastle) as part of London number theory seminar\n\nLecture held in Huxle
y 140\, Imperial College.\n\nAbstract\nFor a positive integer $N$\, denote
by $\\Phi_N(X\,Y)$ the elliptic modular polynomial of level $N$ -- it van
ishes at pairs of $j$-invariants of elliptic curves linked by a cyclic iso
geny of degree $N$ and plays an important role in various cryptosystems. T
he coefficients of $\\Phi_N$ are notoriously large. In this talk\, I prese
nt joint work with Fabien Pazuki and Desir'ee Gij\\'on G\\'omez proving ex
plicit upper and lower bounds on the size of these coefficients.\n
LOCATION:https://researchseminars.org/talk/LNTS/141/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Akinari Hoshi (Niigata University)
DTSTART:20241106T160000Z
DTEND:20241106T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/142
DESCRIPTION:Title: N
orm one tori and Hasse norm principle\nby Akinari Hoshi (Niigata Unive
rsity) as part of London number theory seminar\n\nLecture held in Huxley 1
40\, Imperial College.\n\nAbstract\nLet $k$ be a field and $T$ be an algeb
raic $k$-torus. In 1969\, over a global field $k$\, Voskresenskii proved t
hat there exists an exact sequence $0\\to A(T)\\to H^1(k\,{\\rm Pic}\\\,\\
overline{X})^\\vee\\to Sha(T)\\to 0$ where $A(T)$ is the kernel of the wea
k approximation of $T$\, $Sha(T)$ is the Shafarevich-Tate group of $T$\, $
X$ is a smooth $k$-compactification of $T$\, ${\\rm Pic}\\\,\\overline{X}$
is the Picard group of $\\overline{X}=X\\times_k\\overline{k}$ and $\\vee
$ stands for the Pontryagin dual. On the other hand\, in 1963\, Ono proved
that for the norm one torus $T=R^{(1)}_{K/k}(G_m)$ of $K/k$\, $Sha(T)=0$
if and only if the Hasse norm principle holds for $K/k$. First\, we determ
ine $H^1(k\,{\\rm Pic}\\\, \\overline{X})$ for algebraic $k$-tori $T$ up t
o dimension $5$. Second\, we determine $H^1(k\,{\\rm Pic}\\\, \\overline{X
})$ for norm one tori $T=R^{(1)}_{K/k}(G_m)$ with $[K:k]\\leq 17$. Third\,
we give a necessary and sufficient condition for the Hasse norm principle
for $K/k$ with $[K:k]\\leq 15$. We also show that $H^1(k\,{\\rm Pic}\\\,
\\overline{X})=0$ or $Z/2Z$ for $T=R^{(1)}_{K/k}(G_m)$ when the Galois gro
up of the Galois closure of $K/k$ is the Mathieu group $M_{11}$ or the Jan
ko group $J_1$. As applications of the results\, we get the group $T(k)/R$
of $R$-equivalence classes over a local field $k$ via Colliot-Th\\'{e}l\\
`{e}ne and Sansuc's formula and the Tamagawa number $\\tau(T)$ over a numb
er field $k$ via Ono's formula $\\tau(T)=|H^1(k\,\\widehat{T})|/|Sha(T)|$.
This is joint work with Kazuki Kanai and Aiichi Yamasaki.\n
LOCATION:https://researchseminars.org/talk/LNTS/142/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kazuma Ohara (MPIM Bonn)
DTSTART:20241113T160000Z
DTEND:20241113T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/143
DESCRIPTION:Title: R
eduction to depth zero for tame p-adic groups via Hecke algebra isomorphis
ms\nby Kazuma Ohara (MPIM Bonn) as part of London number theory semina
r\n\nLecture held in Huxley 140\, Imperial College.\n\nAbstract\nThe categ
ory of smooth complex representations of $p$-adic\ngroups decomposes into
a product of indecomposable full subcategories\,\ncalled Bernstein blocks.
In this talk\, I will explain the result that\nunder a mild tameness cond
ition\, every block is equivalent to a depth-zero\nblock\, which is closel
y related to the representation theory of finite\nreductive groups and muc
h better understood than general blocks. This\nresult is obtained by using
the theory of types and an isomorphism of\nHecke algebras. This is a join
t work with Jeffrey Adler\, Jessica Fintzen\,\nand Manish Mishra.\n
LOCATION:https://researchseminars.org/talk/LNTS/143/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ben Heuer (University of Frankfurt)
DTSTART:20241127T160000Z
DTEND:20241127T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/144
DESCRIPTION:Title: P
ro-étale vector bundles and the p-adic Simpson correspondence\nby Ben
Heuer (University of Frankfurt) as part of London number theory seminar\n
\nLecture held in Huxley 140\, Imperial College.\n\nAbstract\nI will first
explain how various classical problems in p-adic number theory such as Se
n theory can be reinterpreted geometrically in terms of vector bundles on
Scholze's pro-étale site. I will then explain how such pro-étale vector
bundles can be understood systematically by means of "p-adic non-abelian H
odge theory". This is closely related to Faltings' p-adic Simpson correspo
ndence\, relating p-adic representations of fundamental groups of p-adic v
arieties to Higgs bundles. Finally\, I will sketch how moduli spaces of pr
o-étale vector bundles can help understand open questions in Sen theory a
nd the p-adic Simpson correspondence.\n
LOCATION:https://researchseminars.org/talk/LNTS/144/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Siqi Yang (Imperial)
DTSTART:20241120T160000Z
DTEND:20241120T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/145
DESCRIPTION:Title: H
ilbert modular forms and geometric modularity in quadratic case\nby Si
qi Yang (Imperial) as part of London number theory seminar\n\nLecture held
in Huxley 140\, Imperial College.\n\nAbstract\nLet \\rho: G_\\Q \\rightar
row \\GL_2(\\Fpbar) be a continuous\, odd\, irreducible representation. Th
e weight part of Serre's conjecture predicts the minimal weight k (\\geq 2
) such that \\rho arises from a modular eigenform of weight k. It is refin
ed by Edixhoven to include the weight one forms by viewing mod p modular f
orms as sections of certain line bundles on the special fibre of a modular
curve. One of the directions to generalise the weight part of Serre's con
jecture is replacing Q with a totally real field F and replacing modular f
orms with Hilbert modular forms. A conjecture in this setting is formulate
d by Buzzard\, Diamond and Jarvis\, where we have the notion of algebraic
modularity. On the other hand\, a generalisation of Edixhoven's refinement
is considered by Diamond and Sasaki\, where we have the notion of geometr
ic modularity. I will discuss the relation between algebraic and geometric
modularity and show their consistency for the weights in a certain cone\,
under the assumption that F is a real quadratic field in which p is unram
ified.\n
LOCATION:https://researchseminars.org/talk/LNTS/145/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Margherita Pagano (Imperial)
DTSTART:20241204T160000Z
DTEND:20241204T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/146
DESCRIPTION:Title: T
he wild Brauer-Manin obstruction\nby Margherita Pagano (Imperial) as p
art of London number theory seminar\n\nLecture held in Huxley 140\, Imperi
al College.\n\nAbstract\nA way to study rational points on a variety is by
looking at their image in the p-adic points. Some natural questions that
arise are the following: is there any obstruction to weak approximation on
the variety? Which primes might be involved in it? I will explain how pri
mes of good reduction can play a role in the Brauer-Manin obstruction to w
eak approximation\, with particular emphasis on the case of K3 surfaces.\n
LOCATION:https://researchseminars.org/talk/LNTS/146/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Deding Yang (Peking University)
DTSTART:20241211T160000Z
DTEND:20241211T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/147
DESCRIPTION:Title: G
eometry of Shimura varieties and positivity of automorphic line bundles on
Unitary Shimura varieties\nby Deding Yang (Peking University) as part
of London number theory seminar\n\nLecture held in Huxley 140\, Imperial
College.\n\nAbstract\nThe study of coherent cohomology on (the special fib
er of) Shimura varieties has various applications to arithmetic problems\,
like\, \ncongruences of automorphic forms\, weight part of Serre's conjec
ture\, liftability of mod p automorphic forms. One of the basic problems i
s to prove certain automorphic line \nbundles are ample\, which yields van
ishing of coherent cohomology. In this talk\, we start from the ampleness
criterion of modular line bundles on Hilbert modular varieties\, \nand the
n explain how to formulate a generalization to unitary Shimura varieties.
Our final result works for split unitary Shimura varieties.\n
LOCATION:https://researchseminars.org/talk/LNTS/147/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Elvira Lupoian (University College London)
DTSTART:20250122T160000Z
DTEND:20250122T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/148
DESCRIPTION:Title: C
eresa cycles of modular curves\nby Elvira Lupoian (University College
London) as part of London number theory seminar\n\nLecture held in Room 50
5\, Department of Mathematics (25 Gordon St)\, University College London.\
n\nAbstract\nThe Ceresa cycle is an algebraic cycle attached to smooth alg
ebraic curve with a marked point\, which is always homologically trivial.
Ceresa proved that for a very general complex curve of genus at least 3\,
this cycle is not trivial as an element of the Chow group. Notably\, hype
relliptic curves with a Weierstrass point have trivial Ceresa cycle. There
are few other explicit examples where triviality/non-triviality is known.
In this talk I will discuss the non-vanishing of the Ceresa cycle attache
d to the modular curve $X_0(N)$.\n
LOCATION:https://researchseminars.org/talk/LNTS/148/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrea Dotto (King's College London)
DTSTART:20250129T160000Z
DTEND:20250129T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/149
DESCRIPTION:Title: G
elfand--Kirillov dimension and mod $p$ cohomology for quaternion algebras<
/a>\nby Andrea Dotto (King's College London) as part of London number theo
ry seminar\n\nLecture held in Room 505\, Department of Mathematics (25 Gor
don St)\, University College London.\n\nAbstract\nThe Gelfand--Kirillov di
mension is a classical invariant which measures the size of smooth represe
ntations of p-adic groups. It acquired particular relevance in the mod $p$
Langlands program because of work of Breuil--Herzig--Hu--Morra--Schraen\,
who computed it for the mod $p$ cohomology of $\\mathrm{GL}_2$ over total
ly real fields\, and used it to prove several structural properties of the
cohomology. In this talk we will present a simplified proof of this resul
t\, which has the added benefit of working unchanged for nonsplit inner fo
rms of $\\mathrm{GL}_2$. This is joint work with Bao V. Le Hung.\n
LOCATION:https://researchseminars.org/talk/LNTS/149/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Radu Toma (IMJ-PRG)
DTSTART:20250212T160000Z
DTEND:20250212T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/150
DESCRIPTION:Title: T
he size of newforms\nby Radu Toma (IMJ-PRG) as part of London number t
heory seminar\n\nLecture held in Room 505\, Department of Mathematics (25
Gordon St)\, University College London.\n\nAbstract\nGiven an $L^2$-normal
ised newform for $\\mathrm{SL}(n)$\, how large are its values in terms of
its level? The theory of quantum chaos suggests such a newform should be s
mall. I will give an overview of how to show interesting upper bounds usin
g spectral analysis\, Hecke operators\, and geometry of numbers. I will pr
esent the first "non-trivial" bounds in higher rank and talk about interme
diate results of perhaps independent interest\, such as Atkin--Lehner oper
ators for $\\mathrm{SL}(n)$ and a reduction theory with level structure.\n
LOCATION:https://researchseminars.org/talk/LNTS/150/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Han-Ung Kufner (Universität Regensburg)
DTSTART:20250219T160000Z
DTEND:20250219T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/151
DESCRIPTION:Title: D
eligne's conjecture on the critical values of Hecke L-functions\nby Ha
n-Ung Kufner (Universität Regensburg) as part of London number theory sem
inar\n\nLecture held in Room 505\, Department of Mathematics (25 Gordon St
)\, University College London.\n\nAbstract\nWe give a proof of Deligne's c
onjecture for critical algebraic Hecke characters\, which relates the spec
ial value of a Hecke L-function up to a rational factor with a certain per
iod. This generalises a result of Blasius in the case where the Hecke char
acter is defined over a CM-field. In our approach\, we make use of the rec
ently constructed Eisenstein--Kronecker classes of Kings--Sprang\, which a
llow for a cohomological interpretation of the L-value when the field of d
efinition is an arbitrary totally imaginary number field. The key insight
is that these classes can be naturally regarded as de Rham classes of Blas
ius' reflex motive\, which already played a key role in Blasius' proof.\n
LOCATION:https://researchseminars.org/talk/LNTS/151/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chris Keyes (King's College London)
DTSTART:20250305T160000Z
DTEND:20250305T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/152
DESCRIPTION:Title: T
owards Artin's conjecture on $p$-adic quintic forms\nby Chris Keyes (K
ing's College London) as part of London number theory seminar\n\nLecture h
eld in Room 505\, Department of Mathematics (25 Gordon St)\, University Co
llege London.\n\nAbstract\nLet $K/\\mathbb{Q}_p$ be a finite extension wit
h residue field $\\mathbb{F}_q$ and suppose $f(x_0\, \\ldots\, x_n)$ is a
homogeneous polynomial of degree $d$ over $K$. A conjecture\, originally d
ue to Artin\, states that when $d$ is prime and $n \\geq d^2$\, $f=0$ has
a nontrivial solution in $K$. This conjecture is known in degrees 2 and 3
due to Hasse and Lewis\, respectively. It is also "asymptotically true\,"
due to work of Ax and Kochen\, in that it holds when $q$ is sufficiently l
arge with respect to $d$\, though this is difficult to make effective. In
this talk\, we present recent joint work with Lea Beneish in which we prov
e the quintic version of the conjecture holds if $q \\geq 7$. Our methods
include both a refinement to a geometric approach of Leep and Yeomans (who
showed $q \\geq 47$ suffices) and a significant computational component.\
n
LOCATION:https://researchseminars.org/talk/LNTS/152/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Joni Teräväinen (University of Cambridge)
DTSTART:20250319T160000Z
DTEND:20250319T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/153
DESCRIPTION:Title: O
n the exceptional set in the $abc$ conjecture\nby Joni Teräväinen (U
niversity of Cambridge) as part of London number theory seminar\n\nLecture
held in Room 505\, Department of Mathematics (25 Gordon St)\, University
College London.\n\nAbstract\nThe well-known $abc$ conjecture asserts that
for any coprime triple of positive integers satisfying $a+b=c$ the squaref
ree radical of $abc$ satisfies a certain strong inequality. In this talk\,
I will discuss a proof giving the first power-saving improvement over the
trivial bound for the number of exceptions to this conjecture. The proof
is based on a combination of various methods for counting rational points
on curves\, and a combinatorial analysis to patch these cases together. Th
is is joint work with Tim Browning and Jared Lichtman.\n
LOCATION:https://researchseminars.org/talk/LNTS/153/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Harry Schmidt (University of Warwick)
DTSTART:20250326T160000Z
DTEND:20250326T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/154
DESCRIPTION:Title: E
ffective estimates for André-Oort in families of elliptic curves\nby
Harry Schmidt (University of Warwick) as part of London number theory semi
nar\n\nLecture held in Room 505\, Department of Mathematics (25 Gordon St)
\, University College London.\n\nAbstract\nI will present joint work with
Binyamini\, Jones\, Thomas in which we manage to give uniform and effectiv
e proofs of the André-Oort conjecture for families of elliptic curves. Ti
me permitting\, I will discuss possible generalizations of our result to f
amilies of abelian varieties.\n
LOCATION:https://researchseminars.org/talk/LNTS/154/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Herbert Gangl (Durham University)
DTSTART:20250312T160000Z
DTEND:20250312T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/155
DESCRIPTION:Title: M
ultiple polylogarithms\, and Zagier's Conjecture revisited\nby Herbert
Gangl (Durham University) as part of London number theory seminar\n\nLect
ure held in Room 505\, Department of Mathematics (25 Gordon St)\, Universi
ty College London.\n\nAbstract\nDirichlet related the residue at $s=1$ of
the Dedekind zeta function of a number field $F$ (a slight generalisation
of the famous Riemann zeta function) to two important arithmetical notions
: the size of the ideal class group and the `volume' of the unit group in
the number ring $\\mathcal{O}_F$ of $F$. Generalising this surprising conn
ection\, the special values of the Dedekind zeta function of a number fiel
d $F$ at integer argument $n$ should\, according to Zagier's Polylogarithm
Conjecture\, be expressed via a determinant of $F$-values of the $n$-th p
olylogarithm function. Goncharov laid out a vast program incorporating thi
s conjecture using properties of multiple polylogarithms and the structure
of a motivic Lie coalgebra.\nIn this impressionist talk I intend to give
a rough idea of the developments from the early days on\, avoiding most of
the technical bits\, and also hint at a number of recent results for high
er weight\, some in joint work with\, or developed by\, S. Charlton\, D.
Radchenko as well as D. Rudenko and his collaborators.\n
LOCATION:https://researchseminars.org/talk/LNTS/155/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrew Graham (University of Oxford)
DTSTART:20250205T160000Z
DTEND:20250205T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/156
DESCRIPTION:Title: T
he exceptional zero conjecture for $\\mathrm{GL}(3)$\nby Andrew Graham
(University of Oxford) as part of London number theory seminar\n\nLecture
held in Room 505\, Department of Mathematics (25 Gordon St)\, University
College London.\n\nAbstract\nIf $E$ is an elliptic curve over $\\mathbb{Q}
$ with split multiplicative reduction at $p$\, then the $p$-adic $L$-funct
ion associated with $E$ vanishes at $s=1$ independently of whether the com
plex $L$-function vanishes. In this case\, one has an "exceptional zero fo
rmula" relating the first derivative of the $p$-adic $L$-function to the c
omplex $L$-function multiplied by a certain L-invariant. This L-invariant
can be interpreted in several ways -- on the automorphic side for example\
, L-invariants parameterise part of the $p$-adic local Langlands correspon
dence for $\\mathrm{GL}_2(\\mathbb{Q}_p)$.\n\nIn this talk\, I will discus
s an exceptional zero formula for (not necessarily essentially self-dual)
regular algebraic\, cuspidal automorphic representations of $\\mathrm{GL}_
3$ which are Steinberg at $p$. The formula involves an automorphic L-invar
iant constructed by Gehrmann. Joint work with Daniel Barrera and Chris Wil
liams.\n
LOCATION:https://researchseminars.org/talk/LNTS/156/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexandros Konstantinou (University College London)
DTSTART:20250115T160000Z
DTEND:20250115T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/157
DESCRIPTION:Title: I
sogeny decompositions and the Tate--Shafarevich group modulo squares\n
by Alexandros Konstantinou (University College London) as part of London n
umber theory seminar\n\nLecture held in Room 505\, Department of Mathemati
cs (25 Gordon St)\, University College London.\n\nAbstract\nWe present a m
ethod for decomposing abelian varieties up to isogeny using group actions
and finite group representation theory. As an application\, we show that g
iven a square-free natural number n\, there exists an abelian variety with
finite Tate--Shafarevich group of order n times a square.\n
LOCATION:https://researchseminars.org/talk/LNTS/157/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Samir Siksek (University of Warwick)
DTSTART:20250226T143000Z
DTEND:20250226T153000Z
DTSTAMP:20260315T025337Z
UID:LNTS/158
DESCRIPTION:Title: G
alois groups of low degree points on curves\nby Samir Siksek (Universi
ty of Warwick) as part of London number theory seminar\n\nLecture held in
Room 505\, Department of Mathematics (25 Gordon St)\, University College L
ondon.\n\nAbstract\nLow degree points on curves have been subject of inten
se\nstudy for several decades\, but little attention has been paid to the\
nGalois groups of those points. In this talk we recall primitive group\nac
tions\, and focus on low degree points whose Galois group is\nprimitive. W
e shall see that such points are relatively rare\, and that\nthey interfer
e with each other. This talk is based on joint work with\nMaleeha Khawaja.
\n
LOCATION:https://researchseminars.org/talk/LNTS/158/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jeehoon Park (Seoul National University)
DTSTART:20250205T130000Z
DTEND:20250205T140000Z
DTSTAMP:20260315T025337Z
UID:LNTS/159
DESCRIPTION:Title: B
F path integrals for elliptic curves and $p$-adic L-functions\nby Jeeh
oon Park (Seoul National University) as part of London number theory semin
ar\n\nLecture held in Room 505\, Department of Mathematics (25 Gordon St)\
, University College London.\n\nAbstract\nIn this talk\, I will explain an
arithmetic path integral formula for the inverse $p$-adic absolute values
of the $p$-adic L-functions of elliptic curves over the rational numbers
with good ordinary reduction at an odd prime $p$ based on the Iwasawa main
conjecture and Mazur’s control theorem. The talk is based on a joint wo
rk with Junyeong Park.\n
LOCATION:https://researchseminars.org/talk/LNTS/159/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dario Beraldo (UCL)
DTSTART:20250226T160000Z
DTEND:20250226T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/160
DESCRIPTION:Title: T
he Deligne--Milnor formula\nby Dario Beraldo (UCL) as part of London n
umber theory seminar\n\nLecture held in Room 505\, Department of Mathemati
cs (25 Gordon St)\, University College London.\n\nAbstract\nLet $X \\to S$
be a family of algebraic varieties parametrized by an infinitesimal disk
$S$\, possibly of mixed characteristic. Bloch's conductor conjecture expre
sses the difference of the Euler characteristics of the special and generi
c fibers in algebraic and arithmetic terms. I'll describe a proof of some
new cases of this conjecture\, including the case of isolated singularitie
s. The latter was a conjecture of Deligne generalizing Milnor's formula on
vanishing cycles. (This is based on joint work with Massimo Pippi.)\n
LOCATION:https://researchseminars.org/talk/LNTS/160/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ilaria Viglino (EPFL)
DTSTART:20250430T150000Z
DTEND:20250430T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/161
DESCRIPTION:Title: M
oment estimates of module lattice points for effective lattice constructio
ns\nby Ilaria Viglino (EPFL) as part of London number theory seminar\n
\nLecture held in K2.40\, King's Building\, King's College London\, WC2R 2
LS.\n\nAbstract\nWe examine the moments of the number of lattice points in
a fixed ball of volume $V$ for lattices in Euclidean space which are modu
les over the ring of integers of a number field $K$. In particular\, we sh
ow that moments obtained for “lifts of codes” to $\\mathcal{O}_K$-modu
les converge to the Rogers integral formula for the space of free $\\mathc
al{O}_K$-module lattices. This extends work of Rogers for $\\mathbb{Z}$-la
ttices. Joint work with Maryna Viazovska\, Nihar Gargava and Vlad Serban.\
n\nVisitors will need to sign in at the Strand Building reception desk and
receive an events sticker to access the building.\n
LOCATION:https://researchseminars.org/talk/LNTS/161/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tim Santens (University of Cambridge)
DTSTART:20250507T150000Z
DTEND:20250507T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/162
DESCRIPTION:Title: L
eading constant in Malle's conjecture\nby Tim Santens (University of C
ambridge) as part of London number theory seminar\n\nLecture held in K2.40
\, King's Building\, King's College London\, WC2R 2LS.\n\nAbstract\nLet G
be a finite permutation group\, Malle has put forward a conjecture on the
number of G-extensions of a number field of bounded discriminant. There ex
ists a superficially similar conjecture by Manin on the number of points o
f bounded height on varieties. In this talk I will discuss recent efforts
to interpret Malle's conjecture as a form of Manin's conjecture for the st
ack BG. Based on this analogy me and Loughran have given a conjectural int
erpretation of the leading constant in Malle's conjecture.\n
LOCATION:https://researchseminars.org/talk/LNTS/162/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Francesca Balestrieri (American University of Paris)
DTSTART:20250514T150000Z
DTEND:20250514T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/163
DESCRIPTION:Title: T
he quadratic Manin-Peyre conjecture for del Pezzo surfaces\nby France
sca Balestrieri (American University of Paris) as part of London number th
eory seminar\n\nLecture held in K2.40\, King's Building\, King's College L
ondon\, WC2R 2LS.\n\nAbstract\nIn this talk\, we outline a general framewo
rk for the study of the "quadratic" Manin-Peyre conjecture (i.e. the Manin
-Peyre conjecture for symmetric squares of varieties) for del Pezzo surfac
es. We then apply this framework (in conjunction with\, among other things
\, some novel lattice counting techniques) to prove that the quadratic Man
in-Peyre conjecture holds for an infinite family of non-split quadrics. Th
is is joint work with Kevin Destagnol\, Julian Lyczak\, Jennifer Park\, an
d Nick Rome.\n
LOCATION:https://researchseminars.org/talk/LNTS/163/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Katerina Santicola (University of Warwick)
DTSTART:20250521T150000Z
DTEND:20250521T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/164
DESCRIPTION:Title: S
harp interpolation of rational points and post-quantum cryptography\nb
y Katerina Santicola (University of Warwick) as part of London number theo
ry seminar\n\nLecture held in K2.40\, King's Building\, King's College Lon
don\, WC2R 2LS.\n\nAbstract\nFor curves\, it is more or less conjectured t
hat the Chabauty method with the Mordell–Weil sieve will give a polynomi
al-time algorithm for finding the sets of rational points over number fiel
ds. Whether this is true for arbitrary varieties is unclear. Over finite f
ields the situation is different. This is the MQ problem\, which is NP-com
plete. This problem is the essence of multivariate cryptography and forms
the basis of most post-quantum signature schemes. The aim of this talk is
to give an overview of the interpolation of rational subvarieties and disc
uss where this fits in with modern cryptography.\n
LOCATION:https://researchseminars.org/talk/LNTS/164/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sam Chow (University of Warwick)
DTSTART:20250604T150000Z
DTEND:20250604T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/165
DESCRIPTION:Title: S
mooth discrepancy and Littlewood’s conjecture\nby Sam Chow (Universi
ty of Warwick) as part of London number theory seminar\n\nLecture held in
K2.40\, King's Building\, King's College London\, WC2R 2LS.\n\nAbstract\nW
e establish a deterministic analogue of Beck’s local-to-global principle
for Kronecker sequences. This gives rise to a novel reformulation of Litt
lewood’s conjecture in Diophantine approximation.\n
LOCATION:https://researchseminars.org/talk/LNTS/165/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thomas Bloom (University of Manchester)
DTSTART:20250611T150000Z
DTEND:20250611T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/166
DESCRIPTION:Title: N
umbers with small digits in multiple bases\nby Thomas Bloom (Universit
y of Manchester) as part of London number theory seminar\n\nLecture held i
n K2.40\, King's Building\, King's College London\, WC2R 2LS.\n\nAbstract\
nAn old conjecture of Graham asks whether there are infinitely many intege
rs $n$ such that $\\binom{2n}{n}$ is coprime to 105. This is equivalent to
asking whether there are infinitely many integers which only have the dig
its 0\,1 in base 3\, 0\,1\,2 in base 5\, and 0\,1\,2\,3 in base 7. In gene
ral\, one can ask whether there are infinitely many integers which only ha
ve 'small' digits in multiple bases simultaneously. For two bases this was
established in 1975 by Erdos\, Graham\, Ruzsa\, and Straus\, but the case
of three or more bases is much more mysterious. I will discuss recent joi
nt work with Ernie Croot\, in which we prove that (assuming the bases are
sufficiently large) there are infinitely many integers such that almost a
ll of the digits are small in all bases simultaneously.\n
LOCATION:https://researchseminars.org/talk/LNTS/166/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pär Kurlberg (KTH)
DTSTART:20250618T150000Z
DTEND:20250618T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/167
DESCRIPTION:Title: A
Poincare section for horocycle flows: escape of mass\nby Pär Kurlber
g (KTH) as part of London number theory seminar\n\nLecture held in K2.40\,
King's Building\, King's College London\, WC2R 2LS.\n\nAbstract\nMotivate
d by a hyperbolic analog of the Lester-Wigman\n"vanishing area correlation
s"-conjecture for euclidean lattice points we\ninvestigate the dynamical p
roperties of a natural choice of a Poincare\nsection\, associated with H/S
L(2\,Z)\, and the horocycle flow on the upper\nhalf plane H. Since the hor
ocycle *flow* is mixing\, one might hope for\nan easy proof of vanishing a
rea correlations by showing that the\nPoincare map is mixing. However\, no
t only is the Poincare map\nnon-mixing\; even equidistribution/ergodicity
breaks down badly due to\nescape of mass. Amusingly\, we can still show va
nishing of area\ncorrelations (but "for the wrong reason".)\n
LOCATION:https://researchseminars.org/talk/LNTS/167/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ned Carmichael (King's College London)
DTSTART:20250625T150000Z
DTEND:20250625T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/168
DESCRIPTION:Title: S
ums of Hecke Eigenvalues\nby Ned Carmichael (King's College London) as
part of London number theory seminar\n\nLecture held in K2.40\, King's Bu
ilding\, King's College London\, WC2R 2LS.\n\nAbstract\nMotivated by the D
irichlet divisor problem\, which asks for the best possible error term in
the classical asymptotic formula for sums of the divisor function\, we con
sider sums of Hecke eigenvalues attached to holomorphic cusp forms. We dis
cuss some recent results\, which reveal interesting transitions in the ave
rage size of these sums as the length of the sums varies relative to the w
eight of the forms.\n
LOCATION:https://researchseminars.org/talk/LNTS/168/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Happy Uppal (University of Bristol)
DTSTART:20250528T150000Z
DTEND:20250528T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/169
DESCRIPTION:Title: L
ines on del Pezzo surfaces\nby Happy Uppal (University of Bristol) as
part of London number theory seminar\n\nLecture held in K2.40\, King's Bui
lding\, King's College London\, WC2R 2LS.\n\nAbstract\nOne of the crowning
achievements of classical algebraic geometry is the Cayley--Salmon theore
m\, which states that any smooth cubic surface over an algebraically close
d field contains exactly 27 lines. Over more general fields\, however\, th
e situation becomes more subtle: the number of lines depends on the arithm
etic of the field. Segre classified the possible numbers of lines that can
appear on a cubic surface over arbitrary fields and showed that all such
line counts can be realised over the rational numbers.\n\nIn this talk\, I
will discuss joint work with Enis Kaya\, Stephen McKean\, and Sam Streete
r\, in which we extend this perspective to del Pezzo surfaces---a class of
surfaces that includes cubic surfaces. We investigate which line counts c
an occur on del Pezzo surfaces over general fields and how these counts ar
e influenced by the arithmetic of the field. We also explore the analogous
question for conic bundles.\n
LOCATION:https://researchseminars.org/talk/LNTS/169/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adam Morgan (Cambridge University)
DTSTART:20251008T150000Z
DTEND:20251008T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/170
DESCRIPTION:Title: O
n the Hasse principle in twist families\nby Adam Morgan (Cambridge Uni
versity) as part of London number theory seminar\n\nLecture held in Imperi
al College London\, Room 139.\n\nAbstract\nI will discuss joint work with
Alex Bartel in which we study the frequency of failures of the Hasse princ
iple in quadratic twist families of torsors under an abelian variety. The
main technical ingredient is a result on the distribution of 2-Selmer grou
ps in families of twists defined by Frobenian conditions.\n
LOCATION:https://researchseminars.org/talk/LNTS/170/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chengyang Bao (Imperial College London)
DTSTART:20251015T150000Z
DTEND:20251015T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/171
DESCRIPTION:Title: A
pplications of patching the coherent cohomology of modular curves\nby
Chengyang Bao (Imperial College London) as part of London number theory se
minar\n\nLecture held in Imperial College London\, Room 139.\n\nAbstract\n
We apply the Taylor--Wiles--Kisin patching method to study certain partial
normalizations of crystalline deformation rings associated with two-dimen
sional representations \\bar{r} : G_{\\Q_p} \\to \\GL_2(\\F)\, where $\\F$
is a finite field of characteristic $p \\ge 5$. Using the $q$-expansion p
rinciple\, we obtain a multiplicity-one result\, which implies that the pa
rtial normalization of the crystalline deformation ring is Cohen--Macaulay
. As applications\, we give a simple criterion for when a crystalline defo
rmation ring coincides with its partial normalization\, thereby establishi
ng new cases where these rings are Cohen--Macaulay. We also prove a Zarisk
i-density result for crystalline points in characteristic $p$\, and we app
ly our method to deduce a multiplicity-one result for Serre's mod-$p$ quat
ernionic modular forms. \n \nMost of these results originated from attempt
s to explain computational data from my thesis on computing crystalline de
formation rings via the Taylor--Wiles--Kisin patching method. I will concl
ude with some expected properties of crystalline deformation rings suggest
ed by the data that remain open.\n
LOCATION:https://researchseminars.org/talk/LNTS/171/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Federico Scavia (Université Sorbonne Paris Nord)
DTSTART:20251022T150000Z
DTEND:20251022T160000Z
DTSTAMP:20260315T025337Z
UID:LNTS/172
DESCRIPTION:Title: T
he lifting problem for Galois representations\nby Federico Scavia (Uni
versité Sorbonne Paris Nord) as part of London number theory seminar\n\nL
ecture held in Imperial College London\, Room 139.\n\nAbstract\nFor every
finite group H and every finite H-module A\, we determine the subgroup of
negligible classes in H^2(H\, A)\, in the sense of Serre\, over fields wit
h enough roots of unity. As a consequence\, we show that for every odd pri
me p and every field F containing a primitive p-th root of unity\, there e
xists a continuous 3-dimensional mod p representation of the absolute Galo
is group of F(x_1\, ...\, x_p) which does not lift modulo p^2. We also con
struct continuous 5-dimensional Galois representations mod 2 which do not
lift modulo 4. This answers a question of Khare and Serre\, and disproves
a conjecture of Florence. This is joint work with Alexander Merkurjev.\n
LOCATION:https://researchseminars.org/talk/LNTS/172/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Valentijn Karemaker (UvA University of Amsterdam)
DTSTART:20251029T160000Z
DTEND:20251029T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/173
DESCRIPTION:Title: A
rithmetic invariants of supersingular abelian varieties\nby Valentijn
Karemaker (UvA University of Amsterdam) as part of London number theory se
minar\n\nLecture held in Imperial College London\, Room 139.\n\nAbstract\n
We will study the moduli space of abelian varieties in characteristic p an
d in particular its supersingular locus S_g. We will discuss when this loc
us is geometrically irreducible\, thereby solving a “class number one p
roblem” or “Gauss problem” for the number of irreducible component
s\; and when a polarised abelian variety is determined by its p-divisible
group\, solving a Gauss problem for central leaves\, which are the loci
consisting of points whose associated p-divisible groups are isomorphic.
Furthermore\, Oort conjectured that all generic points of S_g have automor
phism group {+/- 1}. We will present our results that settle Oort’s conj
ecture for g=2\,3\,4\, and for all higher even dimensions when p >= 5. Thi
s is based on joint works with Ibukiyama and Yu.\n
LOCATION:https://researchseminars.org/talk/LNTS/173/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Robin Bartlett (Queen Mary University of London)
DTSTART:20251126T160000Z
DTEND:20251126T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/174
DESCRIPTION:Title: I
solating the Hodge type in moduli spaces of crystalline Galois representat
ions\nby Robin Bartlett (Queen Mary University of London) as part of L
ondon number theory seminar\n\nLecture held in Imperial College London\, R
oom 139.\n\nAbstract\nModuli spaces of representations of the absolute Gal
ois group of a p-adic field play an important role in various aspects of t
he Langlands correspondence. In this talk I will focus on cases in which t
he coefficients of these representations also have characteristic p\, and
discuss joint work with Bao Le-Hung and Brandon Levin in which we control
the singularities of these moduli spaces in several new cases. One new ing
redient is a description of integral conditions\, derived from Plücker co
ordinates on the affine Grassmannian\, which cut out the locus with a spec
ific Hodge type. This works for any ramification degree\, and as an applic
ation we can extend modularity lifting theorems proved by Kisin for two di
mensional Galois representations of a totally real number field\, to three
dimensional representations.\n
LOCATION:https://researchseminars.org/talk/LNTS/174/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Steven Groen (UvA University of Amsterdam)
DTSTART:20251203T160000Z
DTEND:20251203T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/175
DESCRIPTION:Title: E
kedahl-Oort strata of double covers in characteristic 2.\nby Steven Gr
oen (UvA University of Amsterdam) as part of London number theory seminar\
n\nLecture held in Imperial College London\, Room 139.\n\nAbstract\nThis t
alk concerns a variant of the Schottky problem\, which asks to classify Ja
cobians among all abelian varieties. In characteristic p\, there is a rich
extra structure to consider. Namely\, in characteristic p\, abelian varie
ties can be partitioned into so-called Ekedahl-Oort strata\, within which
all abelian varieties have isomorphic p-torsion group schemes. From this p
oint of view\, it is fruitful to investigate which p-torsion group schemes
can occur as the p-torsion of the Jacobian of a (specified type of) curve
. In this talk\, we treat the 2-torsion of curves in characteristic 2 that
admit a separable double cover to another curve. Through an analysis of t
he first De Rham cohomology\, we prove that the p-torsion of a double cove
r of an ordinary curve is determined by the ramification breaks of the cov
er. This generalizes a result by Elkin and Pries\, where the base curve is
the projective line and the covers are hyperelliptic curves. When the bas
e curve is not ordinary\, we establish bounds on the Ekedahl-Oort type of
the cover.\n
LOCATION:https://researchseminars.org/talk/LNTS/175/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Domenico Valloni (EPFL Lausanne)
DTSTART:20251210T160000Z
DTEND:20251210T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/176
DESCRIPTION:Title: p
-torsion Brauer classes in positive characteristic\nby Domenico Vallon
i (EPFL Lausanne) as part of London number theory seminar\n\nLecture held
in Imperial College London\, Room 139.\n\nAbstract\nIn this talk\, we will
study p-torsion Brauer classes arising from differential forms in charact
eristic p. We will then explain how such classes contribute to the Brauer
–Manin obstruction. As an application\, we determine the Brauer–Manin
set of varieties that possess “many differential forms\,” and we obtai
n new results on the Brauer–Manin set of supersingular K3 surfaces.\n
LOCATION:https://researchseminars.org/talk/LNTS/176/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Livia Grammatica (Strasbourg University)
DTSTART:20251105T160000Z
DTEND:20251105T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/177
DESCRIPTION:Title: S
moothness of the formal Brauer group\nby Livia Grammatica (Strasbourg
University) as part of London number theory seminar\n\nLecture held in Imp
erial College London\, Room 139.\n\nAbstract\nLet X be a smooth and proper
variety over an algebraically closed field of characteristic p. The forma
l Brauer group of X is the functor which parametrizes deformations of the
trivial Brauer class of X. Under mild assumptions\, it is representable by
a formal group\, closely related to the p-torsion of Br(X). We will give
criteria for this formal group to be smooth in terms of the crystalline co
homology of X\, thus providing a partial answer to a question of Artin-Maz
ur. The strategy is to relate the formal Brauer group to crystalline cohom
ology using the relationship between fppf cohomology\, crystalline cohomol
ogy and the Nygaard filtration. These criteria can be used in practice to
produce varieties with non-smooth formal Brauer group\, which are construc
ted as higher-dimensional analogues of Igusa's surface with non-smooth Pic
ard group.\n
LOCATION:https://researchseminars.org/talk/LNTS/177/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bianca Gouthier (MPIM Bonn)
DTSTART:20251112T160000Z
DTEND:20251112T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/178
DESCRIPTION:Title: I
nfinitesimal rational actions on curves\nby Bianca Gouthier (MPIM Bonn
) as part of London number theory seminar\n\nLecture held in Imperial Coll
ege London\, Room 139.\n\nAbstract\nFor any finite $k$-group scheme $G$ ac
ting rationally on a $k$-variety $X$\, if the action is generically free t
hen the dimension of $Lie (G)$ is upper bounded by the dimension of the va
riety.\nThis inequality turns out to be also a sufficient condition for th
e existence of such actions\, when $k$ is a perfect field of positive char
acteristic and $G$ is infinitesimal commutative trigonalizable.\nIn this t
alk\, we will specialize to the case in which $X$ is a curve. First\, we w
ill give an explicit description of all the infinitesimal commutative unip
otent group schemes $G$ with a generically free rational action on $X$ whe
n $k$ is algebraically closed. We will then see how these actions can be c
onstructed\, focusing on the case in which $G$ is the $p$-torsion of a sup
ersingular elliptic curve.\n
LOCATION:https://researchseminars.org/talk/LNTS/178/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sudip Pandit (Kings College London)
DTSTART:20251119T160000Z
DTEND:20251119T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/179
DESCRIPTION:Title: D
elta isocrystal and crystalline cohomology of abelian schemes\nby Sudi
p Pandit (Kings College London) as part of London number theory seminar\n\
nLecture held in Imperial College London\, Room 139.\n\nAbstract\nGiven an
abelian scheme A over a p-adic ring\, using the theory of arithmetic jets
of A\, one can associate a filtered F-isocrystal\, which is referred to a
s the delta isocrystal associated with A. The delta isocrystal admits a na
tural map to the Hodge sequence of the first de Rham cohomology of A. Rece
ntly\, we have shown that the Frobenius operator on the delta isocrystal i
s compatible with the crystalline Frobenius operator on the de Rham cohomo
logy (under the de Rham-crystalline comparison isomorphism). This allows u
s to derive a comparison result between the delta isocrystal and the cryst
alline cohomology of abelian schemes in the category of filtered F-isocrys
tals. This talk is partly based on joint work with Lance Gurney and Arnab
Saha.\n
LOCATION:https://researchseminars.org/talk/LNTS/179/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Stephanie Chan (University College London)
DTSTART:20260121T160000Z
DTEND:20260121T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/180
DESCRIPTION:Title: P
ointwise bounds for 3-torsion\nby Stephanie Chan (University College L
ondon) as part of London number theory seminar\n\nLecture held in Room 505
\, UCL Maths building\, 25 Gordon Street.\n\nAbstract\nFor $\\ell$ an odd
prime number and $d$ a squarefree integer\, a notable problem in arithmeti
c statistics is to give pointwise bounds for the size of the $\\ell$-torsi
on of the class group of $\\mathbb{Q}(\\sqrt{d})$. This is in general a di
fficult problem\, and unconditional pointwise bounds are only available fo
r $\\ell = 3$ due to work of Pierce\, Helfgott–Venkatesh and Ellenberg
–Venkatesh. The current record due to Ellenberg–Venkatesh is $h_3(d) \
\ll_\\epsilon d^{1/3 + \\epsilon}$. We will discuss how to improve this to
$h_3(d) \\ll d^{0.32}$. This is joint work with Peter Koymans.\n
LOCATION:https://researchseminars.org/talk/LNTS/180/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jef Laga
DTSTART:20260128T160000Z
DTEND:20260128T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/181
DESCRIPTION:by Jef Laga as part of London number theory seminar\n\nLecture
held in Room 505\, UCL Maths building\, 25 Gordon Street.\nAbstract: TBA\
n
LOCATION:https://researchseminars.org/talk/LNTS/181/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Maleeha Khawaja
DTSTART:20260204T160000Z
DTEND:20260204T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/182
DESCRIPTION:by Maleeha Khawaja as part of London number theory seminar\n\n
Lecture held in Room 505\, UCL Maths building\, 25 Gordon Street.\nAbstrac
t: TBA\n
LOCATION:https://researchseminars.org/talk/LNTS/182/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Samuel Le Fourn
DTSTART:20260211T160000Z
DTEND:20260211T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/183
DESCRIPTION:by Samuel Le Fourn as part of London number theory seminar\n\n
Lecture held in Room 505\, UCL Maths building\, 25 Gordon Street.\nAbstrac
t: TBA\n
LOCATION:https://researchseminars.org/talk/LNTS/183/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Trajan Hammonds
DTSTART:20260218T160000Z
DTEND:20260218T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/184
DESCRIPTION:by Trajan Hammonds as part of London number theory seminar\n\n
Lecture held in Room 505\, UCL Maths building\, 25 Gordon Street.\nAbstrac
t: TBA\n
LOCATION:https://researchseminars.org/talk/LNTS/184/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alex Bartel
DTSTART:20260225T160000Z
DTEND:20260225T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/185
DESCRIPTION:by Alex Bartel as part of London number theory seminar\n\nLect
ure held in Room 505\, UCL Maths building\, 25 Gordon Street.\nAbstract: T
BA\n
LOCATION:https://researchseminars.org/talk/LNTS/185/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Izzy Rendell (KCL)
DTSTART:20260304T160000Z
DTEND:20260304T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/186
DESCRIPTION:by Izzy Rendell (KCL) as part of London number theory seminar\
n\nLecture held in Room 505\, UCL Maths building\, 25 Gordon Street.\nAbst
ract: TBA\n
LOCATION:https://researchseminars.org/talk/LNTS/186/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xinchen Miao (Mathematisches Institut Bonn)
DTSTART:20260318T143000Z
DTEND:20260318T153000Z
DTSTAMP:20260315T025337Z
UID:LNTS/187
DESCRIPTION:by Xinchen Miao (Mathematisches Institut Bonn) as part of Lond
on number theory seminar\n\nLecture held in Room 505\, UCL Maths building\
, 25 Gordon Street.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LNTS/187/
END:VEVENT
BEGIN:VEVENT
SUMMARY:James Rawson (University of Glasgow)
DTSTART:20260311T160000Z
DTEND:20260311T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/190
DESCRIPTION:by James Rawson (University of Glasgow) as part of London numb
er theory seminar\n\nLecture held in University College London\, Room 505.
\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LNTS/190/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sacha Mangerel (Durham University)
DTSTART:20260325T160000Z
DTEND:20260325T170000Z
DTSTAMP:20260315T025337Z
UID:LNTS/191
DESCRIPTION:by Sacha Mangerel (Durham University) as part of London number
theory seminar\n\nLecture held in University College London\, Room 505.\n
Abstract: TBA\n
LOCATION:https://researchseminars.org/talk/LNTS/191/
END:VEVENT
END:VCALENDAR