BEGIN:VCALENDAR
VERSION:2.0
PRODID:researchseminars.org
CALSCALE:GREGORIAN
X-WR-CALNAME:researchseminars.org
BEGIN:VEVENT
SUMMARY:Thomas Schick (Georg-August Universität Göttingen)
DTSTART:20200430T140000Z
DTEND:20200430T150000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/1
DESCRIPTION:Title: The codimension 2 index obstruction to positive scalar curvature\nb
y Thomas Schick (Georg-August Universität Göttingen) as part of Online G
APT Seminar\n\n\nAbstract\nWe address the following general question: Give
n a (compact without boundary) manifold M\, does M admit a metric of posit
ive scalar curvature. Very classically\, the Gauss-Bonnet theorem implies
that among the (connected orientable compact) surfaces only the 2-sphere h
as this property.\n\nIn higher dimensions\, the most powerful information
uses the Dirac operator and its index\, and an old observation of Schrödi
nger ("Über das Diracsche Elektron im Schwerefeld") coupling scalar curva
ture to the latter.\n\nWe will quickly introduce classical and more modern
("higher") index theory approaches to this problem\, and then discuss a s
pecial implementation:\n\nHow and why certain submanifolds of codimension
2 act as a vaccine (or poison\, depending on your point of view) and preve
nt the occurrence of positive scalar curvature metrics. Realistically\, th
ere won't be too much time to talk about that.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Ridout (University of Melbourne)
DTSTART:20200625T090000Z
DTEND:20200625T100000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/2
DESCRIPTION:Title: A new approach to W-algebras\nby David Ridout (University of Melbou
rne) as part of Online GAPT Seminar\n\n\nAbstract\nW-algebras are a class
of vertex algebras that find many applications in both mathematics and mat
hematical physics. While some classes of examples are fairly well-underst
ood\, they are still quite mysterious. Here\, I want to review some of wh
at's known and then sketch (in a not-too-technical fashion) a promising ne
w approach to W-algebras and their representations based on old work of Se
mikhatov and recent work of Adamović.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:César Galindo (Universidad de los Andes / Universität Hamburg)
DTSTART:20201008T130000Z
DTEND:20201008T140000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/3
DESCRIPTION:Title: Braided Zesting and its applications\nby César Galindo (Universida
d de los Andes / Universität Hamburg) as part of Online GAPT Seminar\n\n\
nAbstract\nIn this talk\, I will introduce a construction of new braided f
usion categories from a given category known as zesting. This method has b
een used in the past to provide categorifications of new fusion rule algeb
ras\, modular data\, and minimal modular extensions of super-modular categ
ories. We will present a complete obstruction theory and parametrisation
approach to the construction and illustrate its utility with several examp
les.\n\nThe talk is based on the manuscript https://arxiv.org/abs/2005.055
44 a joint work with Colleen Delaney\, Julia Plavnik\, Eric C. Rowell\, an
d Qing Zhang.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:James Walton (University of Nottingham)
DTSTART:20201022T141000Z
DTEND:20201022T151000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/4
DESCRIPTION:Title: Aperiodic Order: The Mathematics of Systems of Approximate Symmetry
\nby James Walton (University of Nottingham) as part of Online GAPT Semina
r\n\n\nAbstract\nSymmetry is frequently exploited in Mathematics\, but the
re are many situations in which systems exhibit long-range recurrence with
out precise periodic repetition. A simple example is given by a coding of
an irrational circle rotation. With Shechtman's discovery of quasicrystals
- physical materials with long-range order but also rotational symmetry p
recluding the standard periodicity of usual crystals - it seems that "aper
iodically ordered" patterns can appear in nature too. In this talk I will
introduce the field of Aperiodic Order\, which investigates intriguing inf
inite idealisations of such patterns. A prototypical family of examples is
given by Penrose's famous rhomb\, or kite and dart tilings. I will then e
xplain what sorts of mathematical structures can be introduced to systemis
e their study. I will focus on the construction of the tiling space of an
aperiodic pattern\, through which one may construct fundamental invariants
using standard tools from Algebraic Topology.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Irakli Patchkoria (University of Aberdeen)
DTSTART:20201029T151000Z
DTEND:20201029T161000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/5
DESCRIPTION:Title: Equivariant Stallings-Swan theorem and cohomology of orbit categories\nby Irakli Patchkoria (University of Aberdeen) as part of Online GAPT S
eminar\n\n\nAbstract\nGiven a discrete group G and a family of subgroups F
\, a conjecture in geometric group theory asserts that the geometric dimen
sion of G with respect to F is equal to 1 if and only if the cohomological
dimension of the orbit category O_F(G) associated to F is equal to 1. The
conjecture is known to be true for certain families: the trivial family (
Stallings-Swan)\, the family of all finite subgroups (Dunwoody)\, and the
family of virtually cyclic subgroups (Degrijse) among others. We prove the
conjecture for any family F which does not contain the family of all fini
te subgroups. As a consequence one obtains a cohomological characterisatio
n of free groups with an action of finite group and invariant basis. This
is an equivariant version of the classical Stallings-Swan theorem. We will
also discuss applications to the equivariant LS category. The talk will i
ntroduce basic concepts at the beginning and should be accessible to a gen
eral audience. This is all joint work with Mark Grant and Ehud Meir.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eric Rowell (Texas A&M University)
DTSTART:20201105T151000Z
DTEND:20201105T161000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/6
DESCRIPTION:Title: Representations of Braid Groups and Motion Groups\nby Eric Rowell (
Texas A&M University) as part of Online GAPT Seminar\n\n\nAbstract\nRepres
entations of braid groups appear in many (related) guises\, as sources of
knot and link invariants\, transfer matrices in statistical mechanics\, qu
antum gates in topological quantum computers and commutativity morphisms i
n braided fusion categories. Regarded as trajectories of points in the pl
ane\, the natural generalization of braid groups are groups of motions of
links in 3 manifolds. While much of the representation theory of braid gro
ups and motions groups remains mysterious\, we are starting to see hints t
hat suggest a few conjectures. I will describe a few of these conjectures
and some of the progress towards verification.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eleonore Faber (University of Leeds)
DTSTART:20201112T150000Z
DTEND:20201112T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/7
DESCRIPTION:Title: Infinite constructions: Grassmannian categories of infinite rank and tr
iangulations of an infinity-gon\nby Eleonore Faber (University of Leed
s) as part of Online GAPT Seminar\n\n\nAbstract\nThe homogeneous coordinat
e ring of the Grassmannian of $k$-dimensional subspaces in $n$-space carri
es a natural structure of a cluster algebra. There is an additive categori
fication of this coordinate ring into a so-called Grassmannian cluster cat
egory $C(k\,n)$\, as shown by Jensen\, King\, and Su in 2016. In particula
r\, the cluster category $C(2\,n)$ models triangulations of a regular $n$-
gon. A natural question is\, if there is some kind of limit construction\,
i.e.\, the category ``$C(2\,\\infty)$'' and how to model triangulations o
f a regular ``$\\infty$-gon''.\nThis talk is about a categorification of t
he homogeneous coordinate rings of Grassmannians of infinite rank in terms
of graded maximal Cohen-Macaulay modules/matrix factorizations over a hyp
ersurface singularity. This gives an infinite rank analogue of the categor
ies of Jensen\, King\, and Su. We show that there is a structure preservin
g bijection between the generically free rank one modules in a Grassmannia
n category of infinite rank and the Plücker coordinates in a Grassmannian
cluster algebra of infinite rank. \nIn a special case\, when the hypersur
face singularity is a curve of countable Cohen-Macaulay type\, our categor
y has a combinatorial model by an ``infinity-gon'' and we can determine tr
iangulations of this infinity-gon.\nThis is joint work with Jenny August\,
Man-Wai Cheung\, Sira Gratz\, and Sibylle Schroll.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marius Dadarlat (Purdue University)
DTSTART:20201119T151000Z
DTEND:20201119T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/8
DESCRIPTION:Title: Obstructions to matrix stability of discrete groups\nby Marius Dada
rlat (Purdue University) as part of Online GAPT Seminar\n\n\nAbstract\nA d
iscrete countable group is matricially stable if its finite dimensional ap
proximate unitary representations are perturbable to genuine representatio
ns in the point-norm topology. We aim to explain in accessible terms why
matricial stability for a group G implies the vanishing of the rational ev
en cohomology of G for large classes of groups\, including the linear grou
ps.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Madeleine Jotz-Lean (Georg-August Universität Göttingen)
DTSTART:20201203T151000Z
DTEND:20201203T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/9
DESCRIPTION:Title: Lie groupoids\, Lie algebroids\, representations and ideals\nby Mad
eleine Jotz-Lean (Georg-August Universität Göttingen) as part of Online
GAPT Seminar\n\n\nAbstract\nSymmetries are usually understood as the actio
n of a group. However\, many mathematical objects have a structure that we
recognise as a symmetry\, but which is in fact expressed by a groupoid.\n
\nThis talk motivates the notions of Lie groupoids and Lie algebroids\, an
d explains why the classical notions of representations and ideals are not
sufficient in this context.\n\nRepresentations up to homotopy of Lie alge
broids on graded vector bundles are explained\, in particular the adjoint
representation up to homotopy of a Lie algebroid is described. The graded
trace of the powers of the curvature of a connection up to homotopy induce
s characteristic classes of graded vector bundles. Using these\, one can p
rove obstructions to the existence of a representation up to homotopy on a
graded vector bundle. This gives a further interpretation for the classic
al Pontryagin characters of vector bundles.\n\nAs a consequence\, an obstr
uction to the existence of an infinitesimal ideal system in a Lie algebroi
d is given -- these objects are considered the right notion of ideal in th
e context of Lie algebroids.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andreas Thom (TU Dresden)
DTSTART:20210204T151000Z
DTEND:20210204T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/10
DESCRIPTION:Title: Sofic approximations — what’s the problem?\nby Andreas Thom (T
U Dresden) as part of Online GAPT Seminar\n\n\nAbstract\nI am planning to
give a general introduction to sofic groups\, mention a few applications
to fundamental conjectures about groups and group rings\, and explain Mish
a Gromov’s conjecture that all groups are sofic. Finally I want to disc
uss the notion of stability and present recent progress in the field.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dominic Verdon (University of Bristol)
DTSTART:20210211T151000Z
DTEND:20210211T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/11
DESCRIPTION:Title: Frobenius algebras\, fibre functors and entanglement-assisted transfor
mations of covariant channels\nby Dominic Verdon (University of Bristo
l) as part of Online GAPT Seminar\n\n\nAbstract\nI will first recall that
finite-dimensional C*-algebras and completely positive trace preserving ma
ps precisely correspond to special symmetric Frobenius algebras and counit
-preserving CP morphisms in the category of finite-dimensional Hilbert spa
ces and linear maps. I will extend this result to a Frobenius-algebraic
characterisation of G-C*-algebras and covariant channels for a compact qua
ntum group G\, using Tannaka-Krein-Woronowicz duality for fibre functors o
n the rigid C*-tensor category Rep(G). I will then introduce unitary pseud
onatural transformations (UPTs) between fibre functors\, a higher-dimensio
nal generalisation of unitary monoidal natural transformations\, and show
how these UPTs give rise to reversible entanglement-assisted transformatio
ns of covariant classical and quantum channels generalising quantum telepo
rtation and dense coding.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Karl-Hermann Neeb (FAU Erlangen-Nürnberg)
DTSTART:20210225T151000Z
DTEND:20210225T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/12
DESCRIPTION:Title: A representation theoretic perspective on modular theory\nby Karl-
Hermann Neeb (FAU Erlangen-Nürnberg) as part of Online GAPT Seminar\n\n\n
Abstract\nModular theory is an important aspect of the theory of operator
algebras and in the theory of local observables in Algebraic Quantum Field
Theory (AQFT). It creates a one-parameter group of modular automorphisms
from a single state and\, sometimes\, this group represents the flow of ti
me (the dynamics) in a space-time domain. We study this question from a re
presentation theoretic perspective by asking questions like: Which one-par
ameter groups of Lie groups can arise in this context as modular groups? T
his leads us to real standard subspaces of a complex Hilbert space\, to an
tiunitary representations and to nets of standard subspaces and operator a
lgebras on causal symmetric spaces.\n\nThis is joint work with Gestur Olaf
sson (Baton Rouge) and Vincenzo Morinelli (Rome)\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jose Perea (Michigan State University)
DTSTART:20210311T151000Z
DTEND:20210311T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/13
DESCRIPTION:Title: Quasiperiodicy in data - an applied topology view\nby Jose Perea (
Michigan State University) as part of Online GAPT Seminar\n\n\nAbstract\nT
he analysis of time-varying systems using topological methods has gained c
onsiderable attention over the last few years. This talk will be about qua
siperiodic recurrence in time series data\; i.e.\, the superposition of pe
riodic oscillators with non-commensurate frequencies. The sliding window (
or time delay) embeddings of such functions can be shown to be dense in hi
gh-dimensional tori\, and we will discuss techniques to study the persiste
nt homology of such sets. Along the way\, we will present a recent Künnet
h theorem for persistent homology\, as well as several applications to dat
a science and engineering.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sara Azzali (Universität Hamburg)
DTSTART:20210304T151000Z
DTEND:20210304T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/14
DESCRIPTION:Title: Talk cancelled/postponed\nby Sara Azzali (Universität Hamburg) as
part of Online GAPT Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Florencia Orosz Hunziker (University of Colorado)
DTSTART:20210318T151000Z
DTEND:20210318T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/15
DESCRIPTION:Title: Tensor categories for non-rational Virasoro vertex algebras\nby Fl
orencia Orosz Hunziker (University of Colorado) as part of Online GAPT Sem
inar\n\n\nAbstract\nThe minimal models are representations of the Virasoro
algebra for particular central charges $c_{p\,q}$. For these central char
ges the category of representations has finitely many irreducibles which g
ive rise to a rational conformal field theory. In this talk\, we focus on
the non rational central charges where the number of irreducible represent
ations is infinite. In particular\, we prove that there is a braided tenso
r category structure on a natural subcategory of representations of the Vi
rasoro algebra for arbitrary central charge. \n\nThis talk is based on jo
int work with Thomas Creutzig\, Cuibo Jiang\, David Ridout and Jinwei Yang
.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Roberto Conti (Sapienza Università di Roma)
DTSTART:20210325T151000Z
DTEND:20210325T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/16
DESCRIPTION:Title: Old and news about Cuntz algebras\nby Roberto Conti (Sapienza Univ
ersità di Roma) as part of Online GAPT Seminar\n\n\nAbstract\nThe Cuntz a
lgebras form a prominent family of C*-algebras which\, for one reason or a
nother\, have contributed to shape many aspects of recent research activit
y\, both in the general area of classification of C*-algebras and group ac
tions as well as in Quantum Field Theory\, where they played a central rol
e in the development of abstract forms of Tannaka-Krein dualities.\nIn the
talk I’ll focus on some specific topics taken from a long-term research
project aimed at understanding as much as possible about their automorphi
sms (which might be considered as a very dangerous but fascinating trip in
to a microcosm where algebra\, analysis\, combinatorics\, dynamics\, geome
try etc are all tied up together in various ways).\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thomas Creutzig (University of Alberta)
DTSTART:20210429T141000Z
DTEND:20210429T150000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/17
DESCRIPTION:Title: Vertex Tensor Categories\nby Thomas Creutzig (University of Albert
a) as part of Online GAPT Seminar\n\n\nAbstract\nCategories of modules of
a vertex operator algebra satisfying certain conditions are vertex tensor
categories\, in particular they are braided tensor categories. If these ca
tegories are neither semisimple nor finite\, then it is particularly chall
enging to understand them. I would like to give an overview of this topic\
, explain its relevance and recent progress.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simon Lentner (Universität Hamburg)
DTSTART:20210513T141000Z
DTEND:20210513T150000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/18
DESCRIPTION:Title: Nichols Algebras\, Selberg Integrals and Screening Operators\nby S
imon Lentner (Universität Hamburg) as part of Online GAPT Seminar\n\n\nAb
stract\nNichols Algebras are certain universal algebras associated to brai
dings. They appear as Borel part of quantum groups\, and more generally of
pointed Hopf algebras. Local resp. nonlocal screening operators appear in
conformal field theory\, and their composition is governed by contour int
egrals over singlevalued resp. multivalued analytic functions\, which gene
ralize Selberg integrals\n\nIn my talk I give an introduction to Nichols a
lgebras\, and then I explain my recent result that the relations in a Nich
ols algebra predict zeroes in the Selberg integral. As main application\,
this implies that nonlocal screening operators are described by Nichols al
gebras\, just as local screening operators are usually described by Lie al
gebras. I will not go deep into this\, but I will try to motivate conforma
l field theory and its connection to quantum groups in an illustrative exa
mple.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sara Azzali (Universität Greifswald)
DTSTART:20211021T141000Z
DTEND:20211021T150000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/19
DESCRIPTION:Title: The Baum-Connes correspondence for the pure braid group\nby Sara A
zzali (Universität Greifswald) as part of Online GAPT Seminar\n\n\nAbstra
ct\nThe Baum-Connes conjecture can be seen as a far reaching generalisatio
n of the Atiyah--Singer index theorem. Given a locally compact group $G$\,
the conjecture predicts an isomorphisms between a topological and an anal
ytic object constructed from $G$. One of the main motivations of the Baum-
Connes conjecture comes from the case of discrete groups\, where it implie
s the Novikov conjecture on the homotopy invariance of higher signatures.
We first give an introduction to the topic\, then we look at examples of
explicit computations of the left and right hand side of the Baum-Connes c
orrespondence. In particular we discuss certain braid groups. For this cla
ss of groups the conjecture is known to be true in by results of Oyono-Oyo
no\, Chabert-Echterhoff\, Schick.\n\nThe talk is based on joint work with
Sarah Browne\, Maria Paula Gomez\, Lauren Ruth and Hang Wang.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Magdalena Musat (University of Copenhagen)
DTSTART:20211028T141000Z
DTEND:20211028T150000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/20
DESCRIPTION:Title: talk cancelled\nby Magdalena Musat (University of Copenhagen) as p
art of Online GAPT Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mihály Weiner (Budapest University of Technology and Economics)
DTSTART:20211104T151000Z
DTEND:20211104T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/21
DESCRIPTION:Title: From quantum fields to local algebras: strong locality WITHOUT linear
energy bounds\nby Mihály Weiner (Budapest University of Technology an
d Economics) as part of Online GAPT Seminar\n\n\nAbstract\nA family of qua
ntum fields is said to be strongly local if it generates a\nlocal net of v
on Neumann algebras. Unfortunately\, there have been very\nfew direct meth
ods proposed for showing strong locality of a quantum\nfield. Among them\,
linear energy bounds are the most widely used.\n\nThe problem is especial
ly interesting in the conformal chiral setting\,\nwhere there are plenty o
f existing unitary VOA models\; i.e. quantum fields\ngiven in a rather con
crete manner. However\, a chiral conformal field of\nconformal weight d >
2 cannot admit linear energy bounds. Nevertheless\,\nwe prove that if a ch
iral conformal field satisfies an energy bound of\ndegree d−1\, then i a
lso satisfies a certain local version of the energy\nbound\, and this in t
urn implies strong locality. A central role in our\nproof is played by dif
feomorphism symmetry.\n\nAs a concrete application\, we show that the vert
ex operator algebra given\nby a unitary vacuum representation of the W_3-a
lgebra is strongly local.\nFor central charge c>2\, this yields a new conf
ormal net. We further prove\nthat these nets do not satisfy strong additiv
ity\, and hence are not\ncompletely rational.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nils Carqueville (Universität Wien)
DTSTART:20211111T151000Z
DTEND:20211111T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/22
DESCRIPTION:Title: Fully extended spin TQFTs\nby Nils Carqueville (Universität Wien)
as part of Online GAPT Seminar\n\nLecture held in BigBlueButton.\n\nAbstr
act\nI shall discuss topological quantum field theories on 2-dimensional b
ordisms with spin structures. After reviewing the functorial approach by A
tiyah and Segal\, I will explain what it means for TQFTs to be "extended t
o the point". The general theory will be illustrated by and applied to sta
te sum models\, Landau-Ginzburg models\, and truncated 3-dimensional sigma
models. \n\n(Based on joint work with Lóránt Szegedy\, and with Ilka Br
unner and \nDaniel Roggenkamp.)\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Federico Barbacovi (University College London)
DTSTART:20211118T151000Z
DTEND:20211118T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/23
DESCRIPTION:Title: Categorical dynamics\nby Federico Barbacovi (University College Lo
ndon) as part of Online GAPT Seminar\n\n\nAbstract\nA topological dynamica
l system is given by a topological space $X$ and a continuous map $f : X \
\to X$. To such a couple $(X\,f)$ one can associate an invariant called th
e topological entropy of $f$\, which is a non-negative extended real numbe
r. A famous theorem of Gromov and Yomdin says that when $X$ is a smooth\,
projective variety\, and $f$ is a holomorphic automorphism\, the topologic
al entropy of $f$ can be computed by looking at the action of $f$ on the (
algebraic part of the) cohomology. For the derived-category-minded geomete
r\, it is therefore natural to ask whether such result is the shadow of so
me statement that holds at the level of derived categories.\nIn this talk
I will introduce the notion of categorical dynamical system as defined by
Dimitrov-Haiden-Katzarkov-Kontsevich and I will report on joint work with
Jongmyeong Kim in which we tackle Kikuta-Takahashi’s conjecture (which w
ill be introduced during the talk) both in the negative direction (produci
ng new counterexamples) and positive direction (giving condition that ensu
re that it holds - at least in a weak sense).\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Penneys (The Ohio State University)
DTSTART:20211202T151000Z
DTEND:20211202T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/25
DESCRIPTION:Title: Fusion categories in mathematics and physics\nby David Penneys (Th
e Ohio State University) as part of Online GAPT Seminar\n\n\nAbstract\nCla
ssically\, the notion of symmetry is described by a group. In recent decad
es\, we have seen the emergence of quantum mathematical objects whose symm
etries are best described by tensor categories. Fusion categories simultan
eously generalize the notion of a finite group and its category of finite
dimensional complex representations\, and we think of these objects as enc
oding quantum symmetries. We will give a basic introduction to the theory
of fusion categories and describe applications to some areas of mathematic
s and physics\, namely operator algebras and theoretical condensed matter.
\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Corey Jones (North Carolina State University)
DTSTART:20211209T151000Z
DTEND:20211209T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/26
DESCRIPTION:Title: Braided tensor categories from von Neumann algebras\nby Corey Jone
s (North Carolina State University) as part of Online GAPT Seminar\n\n\nAb
stract\nIn the setting of algebraic quantum field theory\, the superselect
ion sectors of a net of von Neumann algebras naturally form a braided tens
or category. In this talk we will explain an analogous construction whic
h assigns a braided tensor category to a single von Neumann algebra\, desp
ite the absence of spatial degrees of freedom. Our construction builds on
the work of Connes\, Jones and Popa\, and extends Connes' $\\chi(M)$ invar
iant. We will highlight several parallels to the theory of conformal nets\
, and show that for any finite depth inclusion $N\\subseteq M$ of non-Gamm
a $II_1$ factors\, the braided tensor category associated to the envelopin
g algebra $M_{\\infty}$ is the Drinfeld center of the original standard in
variant.\n\nBased on joint work with Quan Chen and David Penneys.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christian Hagendorf (Université catholique de Louvain)
DTSTART:20211216T151000Z
DTEND:20211216T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/27
DESCRIPTION:Title: talk postponed\nby Christian Hagendorf (Université catholique de
Louvain) as part of Online GAPT Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Magdalena Musat (Københavns Universitet)
DTSTART:20220217T151000Z
DTEND:20220217T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/28
DESCRIPTION:Title: On the convex structure of unital quantum channels\, factorizability a
nd the Connes Embedding Problem\nby Magdalena Musat (Københavns Unive
rsitet) as part of Online GAPT Seminar\n\n\nAbstract\nFactorizable quantum
channels\, introduced by C. Anantharaman-Delaroche within the framework
of operator algebras\, have recently found important applications in the a
nalysis of quantum information theory\, revealing new infinite dimensional
phenomena\, and leading also to reformulations of the celebrated Connes E
mbedding Problem. In recent work with M. Rørdam\, we show that (infinite
dimensional) von Neumann algebras are\, indeed\, needed to describe such
channels. Along the way\, I will explain some of the several facets of the
Connes Embedding Problem\, with particular emphasis on the related interp
lay between operator algebras and quantum information theory.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christian Hagendorf (Université catholique de Louvain)
DTSTART:20220224T151000Z
DTEND:20220224T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/29
DESCRIPTION:Title: The supersymmetric eight-vertex model\nby Christian Hagendorf (Uni
versité catholique de Louvain) as part of Online GAPT Seminar\n\n\nAbstra
ct\nThe topic of this talk is the eight-vertex model on the square lattice
. We consider this model at its so-called "supersymmetric" or "combinatori
al point"\, where it presents surprising links to supersymmetry\, enumerat
ive combinatorics and special functions. To illustrate these links\, we di
scuss the model's transfer matrix. Its largest eigenvalue has a particular
ly simple form in the case of an odd number of vertical lines and periodic
boundary conditions along the horizontal direction. We show that several
properties of the corresponding eigenvectors can be expressed in terms of
special polynomials introduced by Rosengren\, Zinn-Justin\, and recently r
elated to the enumeration of three-colourings of the square lattice by Hie
tala.\n\nThis talk is based on joint work with Jean Liénardy and Sandrine
Brasseur and ongoing work with Hjalmar Rosengren.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anne-Laure Thiel (University of Caen)
DTSTART:20220310T151000Z
DTEND:20220310T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/30
DESCRIPTION:Title: A Soergel category for cyclic groups\nby Anne-Laure Thiel (Univers
ity of Caen) as part of Online GAPT Seminar\n\n\nAbstract\nThe category of
Soergel bimodules plays an essential role in (higher) representation theo
ry\, to construct categorical braid group actions and homological invarian
ts of knots. After having briefly recalled the definition and some facts a
bout this category\, the aim of this talk will be to present some of its g
eneralizations. I will focus on a Soergel-like category attached to a cycl
ic group. I will give a complete description of this category through a cl
assification of its indecomposable objects and study its split Grothendiec
k ring. This gives rise to an algebra which is an extension of the Hecke a
lgebra of the cyclic group\, that can be presented by generators and relat
ions. If time permits\, I will mention some partial results about a diagra
mmatic description of this category: how Catalan numbers appear in this co
ntext and how the Temperley-Lieb algebra can describe certain morphism spa
ces in this category. This is joint work with Thomas Gobet.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luca Pol (Universität Regensburg)
DTSTART:20220317T151000Z
DTEND:20220317T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/31
DESCRIPTION:Title: Torsion model for tensor-triangulated categories\nby Luca Pol (Uni
versität Regensburg) as part of Online GAPT Seminar\n\n\nAbstract\nIn thi
s talk I will discuss how one can construct a model for (sufficiently well
-behaved) tensor triangulated categories built from the data of local and
torsion objects. The idea is to mirror constructions in commutative algebr
a such as torsion and localization at prime ideals. I will then discuss tw
o interesting examples arising from algebra and equivariant stable homotop
y theory. This is joint work with S. Balchin\, J.P.C. Greenlees and J. Wil
liamson.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emily Norton (University of Kent)
DTSTART:20220324T151000Z
DTEND:20220324T160000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/32
DESCRIPTION:Title: Calibrated representations of cyclotomic Hecke algebras at roots of un
ity\nby Emily Norton (University of Kent) as part of Online GAPT Semin
ar\n\n\nAbstract\nThe cyclotomic Hecke algebra is a "higher level" version
of the Iwahori-Hecke algebra of the symmetric group. It depends on a coll
ection of parameters\, and its combinatorics involves multipartitions inst
ead of partitions. We are interested in the case when the parameters are r
oots of unity. In general\, we cannot hope for closed-form character formu
las of the irreducible representations. However\, a certain type of repres
entation called "calibrated" is more tractable: those representations on w
hich the Jucys-Murphy elements act semisimply. We classify the calibrated
representations in terms of their Young diagrams\, give a multiplicity-fre
e formula for their characters\, and homologically construct them via BGG
resolutions. This is joint work with Chris Bowman and José Simental.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ramona Wolf (ETH Zürich)
DTSTART:20220331T141000Z
DTEND:20220331T150000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/33
DESCRIPTION:Title: From subfactors to conformal field theories via lattice models\nby
Ramona Wolf (ETH Zürich) as part of Online GAPT Seminar\n\n\nAbstract\nT
here is a long-standing conjecture that to every subfactor\, there exists
a corresponding conformal field theory. Although a considerable amount of
evidence has been collected to support this conjecture\, the general state
ment has not yet been proven or disproven. In the study of this correspond
ence\, it might be helpful to lend methods from physics: Since every subfa
ctors gives rise to two (unitary) fusion categories\, one can imagine atte
mpting to construct counterpart CFTs via lattice models built directly fro
m these categories. In this talk\, I will explain how this construction wo
rks and discuss problems and challenges that occur when carrying it out fo
r relevant examples.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anne-Sophie Kaloghiros (Brunel University London)
DTSTART:20220505T141000Z
DTEND:20220505T150000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/34
DESCRIPTION:Title: 1-dimensional K-moduli spaces of Fano 3-folds\nby Anne-Sophie Kalo
ghiros (Brunel University London) as part of Online GAPT Seminar\n\n\nAbst
ract\nRecent advances in the study of K-stability have shown that there is
a projective good moduli space of K-polystable Q-Gorenstein smoothable Q-
Fano varieties of dimension n and volume V.\n\nThe classification of smoot
h Fano 3-folds is due to Iskovshikh\, Mori and Mukai and dates back to the
80s. While the classification is non-modular\, it contains rich informati
on on the geometry of\nFano 3-folds. Fano 3-folds offer a rich source of e
xamples in which we can explicitly construct and understand some K-moduli
spaces.\n\nIn this talk\, I will discuss some examples of 1-dimensional K-
moduli spaces of Fano 3-folds.\n\nThis is joint work with Abban\, Cheltsov
\, Jiao\, Martinez-Garcia\, Papazachariou and Sarikyan.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simona Paoli (University of Aberdeen)
DTSTART:20220512T141000Z
DTEND:20220512T150000Z
DTSTAMP:20260422T212728Z
UID:OnlineGAPT/35
DESCRIPTION:Title: From Homotopy Theory to Higher categories\nby Simona Paoli (Univer
sity of Aberdeen) as part of Online GAPT Seminar\n\n\nAbstract\nTopologica
l spaces can be studied by breaking them into building blocks\, called $n$
-types\, using a classical construction in homotopy theory\, the Postnikov
decomposition. The desire to model algebraically the building blocks of s
paces was one of the motivations for the development of higher groupoids\,
generalizing the fundamental groupoid of a space. In this talk I will fir
st illustrate how this naturally leads to the need to encode weakly associ
ative and weakly unital compositions of higher morphisms in a higher group
oid and I will discuss the challenges that this poses.\n\nMore generally\,
structures arising in mathematical physics\, namely topological quantum f
ield theories\, call for the need to define a notion of higher category\,
in which higher morphisms are not necessarily invertible.\n\nThe precise f
ormalization of the notions of higher groupoids and higher categories can
be achieved through several combinatorial machineries. I will introduce on
e of the approaches arising from homotopy theory\, based on the notion of
multisimplicial sets. I will finally briefly discuss why this approach is
promising in terms of proving a long-standing open conjecture in higher ca
tegory theory.\n
LOCATION:https://researchseminars.org/talk/OnlineGAPT/35/
END:VEVENT
END:VCALENDAR