BEGIN:VCALENDAR
VERSION:2.0
PRODID:researchseminars.org
CALSCALE:GREGORIAN
X-WR-CALNAME:researchseminars.org
BEGIN:VEVENT
SUMMARY:Adam Logan (Carleton University and Tutte Institute)
DTSTART:20200622T140000Z
DTEND:20200622T150000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/1
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/1/">E
 xplicit coverings of K3 surfaces by squares of curves</a>\nby Adam Logan (
 Carleton University and Tutte Institute) as part of Leiden Algebra\, Geome
 try\, and Number Theory Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rachel Newton (University of Reading)
DTSTART:20200629T140000Z
DTEND:20200629T150000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/2
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/2/">E
 xplicit uniform bounds for Brauer groups of singular K3 surfaces</a>\nby R
 achel Newton (University of Reading) as part of Leiden Algebra\, Geometry\
 , and Number Theory Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matteo Verzobio (Università di Pisa)
DTSTART:20201204T150000Z
DTEND:20201204T160000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/3
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/3/">S
 equences associated to elliptic curves</a>\nby Matteo Verzobio (Universit
 à di Pisa) as part of Leiden Algebra\, Geometry\, and Number Theory Semin
 ar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Raymond van Bommel (MIT)
DTSTART:20201211T150000Z
DTEND:20201211T160000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/4
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/4/">C
 omputation of BSD invariants in higher genus</a>\nby Raymond van Bommel (M
 IT) as part of Leiden Algebra\, Geometry\, and Number Theory Seminar\n\nAb
 stract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lawrence Barrott (Boston College)
DTSTART:20210222T150000Z
DTEND:20210222T160000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/5
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/5/">C
 ounting tangent curves via degenerations</a>\nby Lawrence Barrott (Boston 
 College) as part of Leiden Algebra\, Geometry\, and Number Theory Seminar\
 n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jan Vonk (Universiteit Leiden)
DTSTART:20210301T150000Z
DTEND:20210301T160000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/6
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/6/">Q
 uadratic Chabauty and modular curves</a>\nby Jan Vonk (Universiteit Leiden
 ) as part of Leiden Algebra\, Geometry\, and Number Theory Seminar\n\nAbst
 ract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jana Sotáková (UvA/QuSoft)
DTSTART:20210315T150000Z
DTEND:20210315T160000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/7
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/7/">B
 ruhat-Tits trees and supersingular elliptic curves</a>\nby Jana Sotáková
  (UvA/QuSoft) as part of Leiden Algebra\, Geometry\, and Number Theory Sem
 inar\n\n\nAbstract\nCryptographic schemes based on computing isogenies of 
 supersingular elliptic curves are a fairly young topic in post-quantum cry
 ptography. Their main benefits are their size: public keys are just a few 
 field elements. Their main drawbacks are their speed - and underlying alge
 braic structure\, which has not been explored fully. We will focus on the 
 SIDH family of proposals and propose studying them from the view of Bruhat
 -Tits trees. These trees are simple combinatorial objects\, we can describ
 e them using 2x2 matrices\, and use them to capture the information on tor
 sion points coming from SIDH. This is joint work with Laia Amorós\, Annam
 aria Iezzi\, Kristin Lauter\, and Chloe Martindale.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carlo Pagano (University of Glasgow/MPIM Bonn)
DTSTART:20210322T150000Z
DTEND:20210322T160000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/8
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/8/">O
 n the negative Pell equation</a>\nby Carlo Pagano (University of Glasgow/M
 PIM Bonn) as part of Leiden Algebra\, Geometry\, and Number Theory Seminar
 \n\n\nAbstract\nHow often does the ring of integers of a real quadratic fi
 eld have a unit with norm -1? In 1995 Peter Stevenhagen proposed a precise
  conjectural asymptotic formula describing how many such real quadratic fi
 elds should be out there when counted by discriminant. I will discuss a jo
 int upcoming work with Peter Koymans where we establish Stevenhagen's conj
 ecture.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Owen Biesel (Carleton College)
DTSTART:20210503T140000Z
DTEND:20210503T150000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/9
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/9/">A
  norm functor for quadratic algebras</a>\nby Owen Biesel (Carleton College
 ) as part of Leiden Algebra\, Geometry\, and Number Theory Seminar\n\n\nAb
 stract\nThe trace and norm maps from Galois theory are two members of a me
 nagerie of various norm functors for different types of algebraic data: gi
 ven a ring R with a finite locally-free algebra A (both commutative and un
 ital)\, we can take the trace or norm of an element of A to get an element
  of R\, we can take the "norm" of a line bundle over A to get a line bundl
 e over R\, and thanks to Ferrand we can even take an arbitrary A-module an
 d construct its "norm" as an R-module. In this talk we construct a norm fu
 nctor for the data of a quadratic algebra: given a locally-free rank-2 A-a
 lgebra D\, we produce a locally-free rank-2 R-algebra Nm(D) in a way that 
 is compatible with other norm functors and which extends a known construct
 ion for étale quadratic algebras. We also conjecture a relationship betwe
 en discriminant algebras and this new norm functor.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mirko Mauri (MPIM Bonn)
DTSTART:20210329T140000Z
DTEND:20210329T150000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/10
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/10/">
 Intersection cohomology of character varieties of rank two</a>\nby Mirko M
 auri (MPIM Bonn) as part of Leiden Algebra\, Geometry\, and Number Theory 
 Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giulio Orecchia (EPFL)
DTSTART:20210419T140000Z
DTEND:20210419T150000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/11
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/11/">
 Beschrijving: Title: From algebra to topology: the fundamental group via F
 robenius</a>\nby Giulio Orecchia (EPFL) as part of Leiden Algebra\, Geomet
 ry\, and Number Theory Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rosa Schwarz (Universiteit Leiden)
DTSTART:20210531T140000Z
DTEND:20210531T150000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/12
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/12/">
 The double-double ramification cycle</a>\nby Rosa Schwarz (Universiteit Le
 iden) as part of Leiden Algebra\, Geometry\, and Number Theory Seminar\n\n
 Abstract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xavier Caruso (CNRS/Université de Bordeaux)
DTSTART:20210614T140000Z
DTEND:20210614T150000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/13
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/13/">
 Fast evaluation of some p-adic special functions</a>\nby Xavier Caruso (CN
 RS/Université de Bordeaux) as part of Leiden Algebra\, Geometry\, and Num
 ber Theory Seminar\n\n\nAbstract\nIn this talk\, I will present fast algor
 ithms for computing values of p-adic functions which are solutions of a sm
 all linear differential equation. This includes in particular exponentials
 \, polylogarithms\, hypergeometric functions and many special functions ap
 pearing in the cohomology of p-adic fibrations.\nAs an application\, build
 ing upon previous works by Asakura and Kedlaya\, I will derive an algorith
 m for computing special values of the Dwork hypergeometric function with q
 uasi-linear runtime with respect to the target precision.\nJoint work with
  Marc Mezzarobba\, Nobuki Takayama and Tristan Vaccon.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Elie Eid (Université de Rennes 1)
DTSTART:20210628T140000Z
DTEND:20210628T150000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/15
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/15/">
 Computing Cantor division polynomials via differential equations</a>\nby E
 lie Eid (Université de Rennes 1) as part of Leiden Algebra\, Geometry\, a
 nd Number Theory Seminar\n\n\nAbstract\nThe computation of Cantor division
  polynomials is an essential step in Pila's algorithm for counting points 
 on hyperelliptic curves and their Jacobians over finite fields. Classical 
 algorithms for computing these polynomials are usually based on Cantor’s
  recurrence formulas and Cantor’s algorithm for adding points on Jacobia
 ns. Although\, they exhibit acceptable running time in practice\, their th
 eoretical complexity has not been well studied yet and experiments show th
 at they become much slower when the degree or the genus get higher.\nIn th
 is talk\, I will provide an efficient way to calculate them\, based on sol
 ving some non-linear differential equations.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Evis Ieronymou (University of Cyprus)
DTSTART:20211115T151500Z
DTEND:20211115T161500Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/16
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/16/">
 Brauer-Manin obstruction and zero-cycles on surfaces</a>\nby Evis Ieronymo
 u (University of Cyprus) as part of Leiden Algebra\, Geometry\, and Number
  Theory Seminar\n\n\nAbstract\nWe give an introduction on the Brauer-Manin
  obstruction to the Hasse principle and present some recent results on zer
 o-cycles on surfaces.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rachel Newton (King's College London)
DTSTART:20211117T151500Z
DTEND:20211117T161500Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/17
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/17/">
 Arithmetic of rational points and zero-cycles on Kummer varieties</a>\nby 
 Rachel Newton (King's College London) as part of Leiden Algebra\, Geometry
 \, and Number Theory Seminar\n\n\nAbstract\nIn 1970\, Manin observed that 
 the Brauer group Br(X) of a variety X over a number field K can obstruct t
 he Hasse principle on X. In other words\, the lack of a K-point on X despi
 te the existence of points over every completion of K is sometimes explain
 ed by non-trivial elements in Br(X). This so-called Brauer-Manin obstructi
 on may not always suffice to explain the failure of the Hasse principle bu
 t it is known to be sufficient for some classes of varieties (e.g. torsors
  under connected algebraic groups) and conjectured to be sufficient for ra
 tionally connected varieties and K3 surfaces.\nA zero-cycle on X is a form
 al sum of closed points of X. A rational point of X over K is a zero-cycle
  of degree 1. It is interesting to study the zero-cycles of degree 1 on X\
 , as a generalisation of the rational points. Yongqi Liang has shown that 
 for rationally connected varieties\, sufficiency of the Brauer-Manin obstr
 uction to the Hasse principle for rational points over all finite extensio
 ns of K implies sufficiency of the Brauer-Manin obstruction to the Hasse p
 rinciple for zero-cycles of degree 1 over K. In this talk\, I will discuss
  joint work with Francesca Balestrieri where we extend Liang's result to K
 ummer varieties.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Leo Herr (University of Utah)
DTSTART:20211122T151500Z
DTEND:20211122T161500Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/18
DESCRIPTION:by Leo Herr (University of Utah) as part of Leiden Algebra\, G
 eometry\, and Number Theory Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emre Sertöz (Leibniz Universität Hannover)
DTSTART:20211201T151500Z
DTEND:20211201T161500Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/19
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/19/">
 Separating periods of quartic surfaces</a>\nby Emre Sertöz (Leibniz Unive
 rsität Hannover) as part of Leiden Algebra\, Geometry\, and Number Theory
  Seminar\n\n\nAbstract\nWe give an effective lower bound on the distance b
 etween two distinct periods of a given quartic surface defined over the al
 gebraic numbers. The main ingredient is the determination of height bounds
  on components of the Noether--Lefschetz loci. This makes it possible to s
 tudy the Diophantine properties of periods of quartic surfaces and to cert
 ify a part of the numerical computation of their Picard groups. This is jo
 int work with Pierre Lairez.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sergej Monavari (Universiteit Utrecht)
DTSTART:20211208T151500Z
DTEND:20211208T161500Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/20
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/20/">
 Higher rank K-theoretic Donaldson-Thomas Theory of points</a>\nby Sergej M
 onavari (Universiteit Utrecht) as part of Leiden Algebra\, Geometry\, and 
 Number Theory Seminar\n\n\nAbstract\nA classical way to produce invariants
  is through intersection theory\, usually on a smooth projective variety. 
 We give a gentle introduction on how to use torus actions to refine invari
 ants in several directions\, for example K-theoretic and virtual invariant
 s. As a concrete example\, we explain how to extract meaningful invariants
  from the Quot schemes of quasi-projective smooth toric threefolds and how
  to refine them. We present and prove various closed formulas for differen
 t flavours of higher rank Donaldson-Thomas invariants of points\, solving 
 a series of conjectures proposed in String Theory. This is based on joint 
 work with N. Fasola and A. Ricolfi.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Priyanka Majumder (Darmstadt)
DTSTART:20220209T151500Z
DTEND:20220209T161500Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/21
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/21/">
 Bounds for canonical Green’s functions of Fuchsian subgroups of PSL2(R)<
 /a>\nby Priyanka Majumder (Darmstadt) as part of Leiden Algebra\, Geometry
 \, and Number Theory Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Shengyuan Huang (Birmingham)
DTSTART:20220221T151500Z
DTEND:20220221T161500Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/22
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/22/">
 Lie structures in derived categories</a>\nby Shengyuan Huang (Birmingham) 
 as part of Leiden Algebra\, Geometry\, and Number Theory Seminar\n\n\nAbst
 ract\nFor a closed embedding $X\\hookrightarrow S$ of smooth schemes with 
 a first order splitting\, the derived self-intersection $X\\times^R_SX$ an
 d the shifted normal bundle $N_{X/S}[-1]$ carry Lie structures. In this ta
 lk\, we discuss an analogue of the exponential map from a Lie algebra to t
 he corresponding Lie group in this setting and its application in the stud
 y of orbifold Hochschild cohomology product.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giacomo Mezzedimi (Hannover)
DTSTART:20220228T151500Z
DTEND:20220228T161500Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/23
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/23/">
 Projective models of Enriques surfaces via elliptic curves</a>\nby Giacomo
  Mezzedimi (Hannover) as part of Leiden Algebra\, Geometry\, and Number Th
 eory Seminar\n\n\nAbstract\nEnriques surfaces form one of the four classes
  of algebraic surfaces of Kodaira dimension zero in the Enriques-Kodaira c
 lassification. The first examples of Enriques surfaces were constructed by
  Enriques as minimal desingularizations of certain non-normal sextics in P
 ^3\, which are now called Enriques sextics. The goal of this talk will be 
 to show that every Enriques surface over an algebraically closed field of 
 characteristic different from 2 can be realized as the minimal desingulari
 zation of an Enriques sextic. I will introduce the main tool used in the p
 roof\, namely isotropic sequences\, and I will show how the presence of ma
 ny elliptic fibrations on the surface leads to "good" projective models. I
  will then discuss some geometric implications of the result and some rele
 vant examples. This is joint work in progress with Gebhard Martin and Davi
 de Veniani.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tommy Hofmann (Siegen)
DTSTART:20220307T151500Z
DTEND:20220307T161500Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/24
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/24/">
 Lattice isomorphism and the integral matrix similarity problem</a>\nby Tom
 my Hofmann (Siegen) as part of Leiden Algebra\, Geometry\, and Number Theo
 ry Seminar\n\n\nAbstract\nDeciding whether two lattices over orders of fin
 ite-dimensional algebras over number fields is a classical problem in algo
 rithmic number theory. We present a new algorithm for this problem\, assum
 ing that the Wedderburn decomposition of the algebra behaves nice. As an a
 pplication we discuss the connection to the similarity problem for integra
 l matrices (the conjugacy problem in GL(n\, Z)).\nThe resulting algorithm 
 for the latter problem is the first with proven complexity and performs ve
 ry well in practice. This is joint work with Werner Bley and Henri Johnsto
 n.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vova Soslino (St. Petersburg/Regensburg)
DTSTART:20220315T111500Z
DTEND:20220315T121500Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/25
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/25/">
 Weight structures and applications I: structural results</a>\nby Vova Sosl
 ino (St. Petersburg/Regensburg) as part of Leiden Algebra\, Geometry\, and
  Number Theory Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Elden Elmanto (Harvard)
DTSTART:20220316T151500Z
DTEND:20220316T161500Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/26
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/26/">
 Weight structures and applications II: affine stacks and noncommutative Ho
 dge theory</a>\nby Elden Elmanto (Harvard) as part of Leiden Algebra\, Geo
 metry\, and Number Theory Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/LAGeNT/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Libby Taylor (Stanford)
DTSTART:20220425T170000Z
DTEND:20220425T180000Z
DTSTAMP:20260422T225848Z
UID:LAGeNT/27
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/LAGeNT/27/">
 Higher Brauer groups and higher Azumaya algebras</a>\nby Libby Taylor (Sta
 nford) as part of Leiden Algebra\, Geometry\, and Number Theory Seminar\n\
 n\nAbstract\nLet X be some scheme.  We are all familiar with the fact that
  classes in H^1(X\,G_m) correspond to line bundles\, or invertible sheaves
 .  Most of us have also seen the interpretation of H^2(X\,G_m) as Azumaya 
 algebras\, which are invertible bundles up to Morita equivalence.  This ra
 ises the question: what about H^3\, or H^4\, or H^n?  Can they be interpre
 ted as some kind of invertible objects over X?  For H^3\, the answer turns
  out to be yes\, and we will describe objects we call 2-Azumaya algebras w
 hich provide such an interpretation.\n
LOCATION:https://researchseminars.org/talk/LAGeNT/27/
END:VEVENT
END:VCALENDAR