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:20260404T094701Z
UID:OnlineGAPT/1
DESCRIPTION:Title: The codimension 2 index obstruction to positive scalar curvature
\nby Thomas Schick (Georg-August Universität Göttingen) as part of O
nline GAPT Seminar\n\n\nAbstract\nWe address the following general questio
n: Given a (compact without boundary) manifold M\, does M admit a metric o
f positive scalar curvature. Very classically\, the Gauss-Bonnet theorem i
mplies that among the (connected orientable compact) surfaces only the 2-s
phere has this property.\n\nIn higher dimensions\, the most powerful infor
mation uses the Dirac operator and its index\, and an old observation of S
chrödinger ("Über das Diracsche Elektron im Schwerefeld") coupling scala
r curvature to the latter.\n\nWe will quickly introduce classical and more
modern ("higher") index theory approaches to this problem\, and then disc
uss a special implementation:\n\nHow and why certain submanifolds of codim
ension 2 act as a vaccine (or poison\, depending on your point of view) an
d prevent the occurrence of positive scalar curvature metrics. Realistical
ly\, there won't be too much time to talk about that.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Ridout (University of Melbourne)
DTSTART:20200625T090000Z
DTEND:20200625T100000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/2
DESCRIPTION:Title: A new approach to W-algebras\nby David Ridout (University of
Melbourne) 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 mathematical physics. While some classes of examples are fairly well-
understood\, they are still quite mysterious. Here\, I want to review som
e of what's known and then sketch (in a not-too-technical fashion) a promi
sing new approach to W-algebras and their representations based on old wor
k of Semikhatov and recent work of Adamović.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:César Galindo (Universidad de los Andes / Universität Hamburg)
DTSTART:20201008T130000Z
DTEND:20201008T140000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/3
DESCRIPTION:Title: Braided Zesting and its applications\nby César Galindo (Uni
versidad de los Andes / Universität Hamburg) as part of Online GAPT Semin
ar\n\n\nAbstract\nIn this talk\, I will introduce a construction of new br
aided fusion categories from a given category known as zesting. This metho
d has been used in the past to provide categorifications of new fusion rul
e algebras\, modular data\, and minimal modular extensions of super-modula
r categories. We will present a complete obstruction theory and parametri
sation approach to the construction and illustrate its utility with severa
l examples.\n\nThe talk is based on the manuscript https://arxiv.org/abs/2
005.05544 a joint work with Colleen Delaney\, Julia Plavnik\, Eric C. Rowe
ll\, and Qing Zhang.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:James Walton (University of Nottingham)
DTSTART:20201022T141000Z
DTEND:20201022T151000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/4
DESCRIPTION:Title: Aperiodic Order: The Mathematics of Systems of Approximate Symme
try\nby James Walton (University of Nottingham) as part of Online GAPT
Seminar\n\n\nAbstract\nSymmetry is frequently exploited in Mathematics\,
but there are many situations in which systems exhibit long-range recurren
ce without precise periodic repetition. A simple example is given by a cod
ing of an irrational circle rotation. With Shechtman's discovery of quasic
rystals - physical materials with long-range order but also rotational sym
metry precluding the standard periodicity of usual crystals - it seems tha
t "aperiodically ordered" patterns can appear in nature too. In this talk
I will introduce the field of Aperiodic Order\, which investigates intrigu
ing infinite idealisations of such patterns. A prototypical family of exam
ples is given by Penrose's famous rhomb\, or kite and dart tilings. I will
then explain what sorts of mathematical structures can be introduced to s
ystemise their study. I will focus on the construction of the tiling space
of an aperiodic pattern\, through which one may construct fundamental inv
ariants using standard tools from Algebraic Topology.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Irakli Patchkoria (University of Aberdeen)
DTSTART:20201029T151000Z
DTEND:20201029T161000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/5
DESCRIPTION:Title: Equivariant Stallings-Swan theorem and cohomology of orbit categ
ories\nby Irakli Patchkoria (University of Aberdeen) as part of Online
GAPT Seminar\n\n\nAbstract\nGiven a discrete group G and a family of subg
roups F\, a conjecture in geometric group theory asserts that the geometri
c dimension of G with respect to F is equal to 1 if and only if the cohomo
logical 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 f
amily (Stallings-Swan)\, the family of all finite subgroups (Dunwoody)\, a
nd the family of virtually cyclic subgroups (Degrijse) among others. We pr
ove the conjecture for any family F which does not contain the family of a
ll finite subgroups. As a consequence one obtains a cohomological characte
risation 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 introduce basic concepts at the beginning and should be accessible t
o a general audience. This is all joint work with Mark Grant and Ehud Meir
.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eric Rowell (Texas A&M University)
DTSTART:20201105T151000Z
DTEND:20201105T161000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/6
DESCRIPTION:Title: Representations of Braid Groups and Motion Groups\nby Eric R
owell (Texas A&M University) as part of Online GAPT Seminar\n\n\nAbstract\
nRepresentations of braid groups appear in many (related) guises\, as sour
ces of knot and link invariants\, transfer matrices in statistical mechani
cs\, quantum gates in topological quantum computers and commutativity morp
hisms in braided fusion categories. Regarded as trajectories of points in
the plane\, the natural generalization of braid groups are groups of moti
ons of links in 3 manifolds. While much of the representation theory of br
aid groups and motions groups remains mysterious\, we are starting to see
hints that suggest a few conjectures. I will describe a few of these conj
ectures and some of the progress towards verification.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eleonore Faber (University of Leeds)
DTSTART:20201112T150000Z
DTEND:20201112T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/7
DESCRIPTION:Title: Infinite constructions: Grassmannian categories of infinite rank
and triangulations of an infinity-gon\nby Eleonore Faber (University
of Leeds) as part of Online GAPT Seminar\n\n\nAbstract\nThe homogeneous co
ordinate ring of the Grassmannian of $k$-dimensional subspaces in $n$-spac
e carries a natural structure of a cluster algebra. There is an additive c
ategorification of this coordinate ring into a so-called Grassmannian clus
ter category $C(k\,n)$\, as shown by Jensen\, King\, and Su in 2016. In pa
rticular\, the cluster category $C(2\,n)$ models triangulations of a regul
ar $n$-gon. A natural question is\, if there is some kind of limit constru
ction\, i.e.\, the category ``$C(2\,\\infty)$'' and how to model triangula
tions of a regular ``$\\infty$-gon''.\nThis talk is about a categorificati
on of the homogeneous coordinate rings of Grassmannians of infinite rank i
n terms of graded maximal Cohen-Macaulay modules/matrix factorizations ove
r a hypersurface singularity. This gives an infinite rank analogue of the
categories of Jensen\, King\, and Su. We show that there is a structure pr
eserving bijection between the generically free rank one modules in a Gras
smannian category of infinite rank and the Plücker coordinates in a Grass
mannian cluster algebra of infinite rank. \nIn a special case\, when the h
ypersurface singularity is a curve of countable Cohen-Macaulay type\, our
category has a combinatorial model by an ``infinity-gon'' and we can deter
mine triangulations of this infinity-gon.\nThis is joint work with Jenny A
ugust\, Man-Wai Cheung\, Sira Gratz\, and Sibylle Schroll.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marius Dadarlat (Purdue University)
DTSTART:20201119T151000Z
DTEND:20201119T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/8
DESCRIPTION:Title: Obstructions to matrix stability of discrete groups\nby Mari
us Dadarlat (Purdue University) as part of Online GAPT Seminar\n\n\nAbstra
ct\nA discrete countable group is matricially stable if its finite dimensi
onal approximate unitary representations are perturbable to genuine repres
entations in the point-norm topology. We aim to explain in accessible ter
ms why matricial stability for a group G implies the vanishing of the rati
onal even cohomology of G for large classes of groups\, including the line
ar groups.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Madeleine Jotz-Lean (Georg-August Universität Göttingen)
DTSTART:20201203T151000Z
DTEND:20201203T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/9
DESCRIPTION:Title: Lie groupoids\, Lie algebroids\, representations and ideals\
nby Madeleine Jotz-Lean (Georg-August Universität Göttingen) as part of
Online GAPT Seminar\n\n\nAbstract\nSymmetries are usually understood as th
e action of a group. However\, many mathematical objects have a structure
that we recognise as a symmetry\, but which is in fact expressed by a grou
poid.\n\nThis talk motivates the notions of Lie groupoids and Lie algebroi
ds\, and explains why the classical notions of representations and ideals
are not sufficient in this context.\n\nRepresentations up to homotopy of L
ie algebroids on graded vector bundles are explained\, in particular the a
djoint 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
induces characteristic classes of graded vector bundles. Using these\, on
e can prove obstructions to the existence of a representation up to homoto
py on a graded vector bundle. This gives a further interpretation for the
classical Pontryagin characters of vector bundles.\n\nAs a consequence\, a
n obstruction to the existence of an infinitesimal ideal system in a Lie a
lgebroid is given -- these objects are considered the right notion of idea
l in the context of Lie algebroids.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andreas Thom (TU Dresden)
DTSTART:20210204T151000Z
DTEND:20210204T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/10
DESCRIPTION:Title: Sofic approximations — what’s the problem?\nby Andreas
Thom (TU Dresden) as part of Online GAPT Seminar\n\n\nAbstract\nI am plann
ing to give a general introduction to sofic groups\, mention a few applic
ations to fundamental conjectures about groups and group rings\, and expla
in Misha Gromov’s conjecture that all groups are sofic. Finally I want
to discuss the notion of stability and present recent progress in the fie
ld.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dominic Verdon (University of Bristol)
DTSTART:20210211T151000Z
DTEND:20210211T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/11
DESCRIPTION:Title: Frobenius algebras\, fibre functors and entanglement-assisted t
ransformations of covariant channels\nby Dominic Verdon (University of
Bristol) as part of Online GAPT Seminar\n\n\nAbstract\nI will first recal
l that finite-dimensional C*-algebras and completely positive trace preser
ving maps precisely correspond to special symmetric Frobenius algebras and
counit-preserving CP morphisms in the category of finite-dimensional Hilb
ert spaces and linear maps. I will extend this result to a Frobenius-alg
ebraic characterisation of G-C*-algebras and covariant channels for a comp
act quantum group G\, using Tannaka-Krein-Woronowicz duality for fibre fun
ctors on the rigid C*-tensor category Rep(G). I will then introduce unitar
y pseudonatural transformations (UPTs) between fibre functors\, a higher-d
imensional generalisation of unitary monoidal natural transformations\, an
d show how these UPTs give rise to reversible entanglement-assisted transf
ormations of covariant classical and quantum channels generalising quantum
teleportation and dense coding.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Karl-Hermann Neeb (FAU Erlangen-Nürnberg)
DTSTART:20210225T151000Z
DTEND:20210225T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/12
DESCRIPTION:Title: A representation theoretic perspective on modular theory\nb
y Karl-Hermann Neeb (FAU Erlangen-Nürnberg) as part of Online GAPT Semina
r\n\n\nAbstract\nModular theory is an important aspect of the theory of op
erator algebras and in the theory of local observables in Algebraic Quantu
m Field Theory (AQFT). It creates a one-parameter group of modular automor
phisms from a single state and\, sometimes\, this group represents the flo
w of time (the dynamics) in a space-time domain. We study this question fr
om a representation theoretic perspective by asking questions like: Which
one-parameter groups of Lie groups can arise in this context as modular gr
oups? This leads us to real standard subspaces of a complex Hilbert space\
, to antiunitary representations and to nets of standard subspaces and ope
rator algebras on causal symmetric spaces.\n\nThis is joint work with Gest
ur Olafsson (Baton Rouge) and Vincenzo Morinelli (Rome)\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jose Perea (Michigan State University)
DTSTART:20210311T151000Z
DTEND:20210311T160000Z
DTSTAMP:20260404T094701Z
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\nAbst
ract\nThe analysis of time-varying systems using topological methods has g
ained considerable attention over the last few years. This talk will be ab
out quasiperiodic recurrence in time series data\; i.e.\, the superpositio
n of periodic oscillators with non-commensurate frequencies. The sliding w
indow (or time delay) embeddings of such functions can be shown to be dens
e in high-dimensional tori\, and we will discuss techniques to study the p
ersistent homology of such sets. Along the way\, we will present a recent
Künneth theorem for persistent homology\, as well as several applications
to data science and engineering.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sara Azzali (Universität Hamburg)
DTSTART:20210304T151000Z
DTEND:20210304T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/14
DESCRIPTION:Title: Talk cancelled/postponed\nby Sara Azzali (Universität Hamb
urg) as part of Online GAPT Seminar\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Florencia Orosz Hunziker (University of Colorado)
DTSTART:20210318T151000Z
DTEND:20210318T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/15
DESCRIPTION:Title: Tensor categories for non-rational Virasoro vertex algebras
\nby Florencia Orosz Hunziker (University of Colorado) as part of Online G
APT Seminar\n\n\nAbstract\nThe minimal models are representations of the V
irasoro algebra for particular central charges $c_{p\,q}$. For these centr
al charges the category of representations has finitely many irreducibles
which give rise to a rational conformal field theory. In this talk\, we fo
cus on the non rational central charges where the number of irreducible re
presentations is infinite. In particular\, we prove that there is a braide
d tensor category structure on a natural subcategory of representations of
the Virasoro algebra for arbitrary central charge. \n\nThis talk is base
d on joint work with Thomas Creutzig\, Cuibo Jiang\, David Ridout and Jinw
ei Yang.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Roberto Conti (Sapienza Università di Roma)
DTSTART:20210325T151000Z
DTEND:20210325T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/16
DESCRIPTION:Title: Old and news about Cuntz algebras\nby Roberto Conti (Sapien
za Università di Roma) as part of Online GAPT Seminar\n\n\nAbstract\nThe
Cuntz algebras form a prominent family of C*-algebras which\, for one reas
on or another\, have contributed to shape many aspects of recent research
activity\, both in the general area of classification of C*-algebras and g
roup actions as well as in Quantum Field Theory\, where they played a cent
ral role 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 r
esearch project aimed at understanding as much as possible about their aut
omorphisms (which might be considered as a very dangerous but fascinating
trip into a microcosm where algebra\, analysis\, combinatorics\, dynamics\
, geometry etc are all tied up together in various ways).\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thomas Creutzig (University of Alberta)
DTSTART:20210429T141000Z
DTEND:20210429T150000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/17
DESCRIPTION:Title: Vertex Tensor Categories\nby Thomas Creutzig (University of
Alberta) as part of Online GAPT Seminar\n\n\nAbstract\nCategories of modu
les of a vertex operator algebra satisfying certain conditions are vertex
tensor categories\, in particular they are braided tensor categories. If t
hese categories are neither semisimple nor finite\, then it is particularl
y challenging to understand them. I would like to give an overview of this
topic\, explain its relevance and recent progress.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simon Lentner (Universität Hamburg)
DTSTART:20210513T141000Z
DTEND:20210513T150000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/18
DESCRIPTION:Title: Nichols Algebras\, Selberg Integrals and Screening Operators\nby Simon Lentner (Universität Hamburg) as part of Online GAPT Seminar\
n\n\nAbstract\nNichols Algebras are certain universal algebras associated
to braidings. They appear as Borel part of quantum groups\, and more gener
ally of pointed Hopf algebras. Local resp. nonlocal screening operators ap
pear in conformal field theory\, and their composition is governed by cont
our integrals over singlevalued resp. multivalued analytic functions\, whi
ch generalize Selberg integrals\n\nIn my talk I give an introduction to Ni
chols algebras\, and then I explain my recent result that the relations in
a Nichols algebra predict zeroes in the Selberg integral. As main applica
tion\, this implies that nonlocal screening operators are described by Nic
hols algebras\, just as local screening operators are usually described by
Lie algebras. I will not go deep into this\, but I will try to motivate c
onformal field theory and its connection to quantum groups in an illustrat
ive example.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sara Azzali (Universität Greifswald)
DTSTART:20211021T141000Z
DTEND:20211021T150000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/19
DESCRIPTION:Title: The Baum-Connes correspondence for the pure braid group\nby
Sara Azzali (Universität Greifswald) as part of Online GAPT Seminar\n\n\
nAbstract\nThe Baum-Connes conjecture can be seen as a far reaching genera
lisation of the Atiyah--Singer index theorem. Given a locally compact grou
p $G$\, the conjecture predicts an isomorphisms between a topological and
an analytic object constructed from $G$. One of the main motivations of th
e Baum-Connes conjecture comes from the case of discrete groups\, where it
implies the Novikov conjecture on the homotopy invariance of higher signa
tures. We first give an introduction to the topic\, then we look at examp
les of explicit computations of the left and right hand side of the Baum-C
onnes correspondence. In particular we discuss certain braid groups. For t
his class of groups the conjecture is known to be true in by results of Oy
ono-Oyono\, Chabert-Echterhoff\, Schick.\n\nThe talk is based on joint wor
k with Sarah Browne\, Maria Paula Gomez\, Lauren Ruth and Hang Wang.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Magdalena Musat (University of Copenhagen)
DTSTART:20211028T141000Z
DTEND:20211028T150000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/20
DESCRIPTION:Title: talk cancelled\nby Magdalena Musat (University of Copenhage
n) as part of Online GAPT Seminar\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mihály Weiner (Budapest University of Technology and Economics)
DTSTART:20211104T151000Z
DTEND:20211104T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/21
DESCRIPTION:Title: From quantum fields to local algebras: strong locality WITHOUT
linear energy bounds\nby Mihály Weiner (Budapest University of Techno
logy and Economics) as part of Online GAPT Seminar\n\n\nAbstract\nA family
of quantum fields is said to be strongly local if it generates a\nlocal n
et of von Neumann algebras. Unfortunately\, there have been very\nfew dire
ct methods proposed for showing strong locality of a quantum\nfield. Among
them\, linear energy bounds are the most widely used.\n\nThe problem is e
specially interesting in the conformal chiral setting\,\nwhere there are p
lenty of existing unitary VOA models\; i.e. quantum fields\ngiven in a rat
her concrete manner. However\, a chiral conformal field of\nconformal weig
ht d > 2 cannot admit linear energy bounds. Nevertheless\,\nwe prove that
if a chiral conformal field satisfies an energy bound of\ndegree d−1\, t
hen i also satisfies a certain local version of the energy\nbound\, and th
is in turn implies strong locality. A central role in our\nproof is played
by diffeomorphism symmetry.\n\nAs a concrete application\, we show that t
he vertex operator algebra given\nby a unitary vacuum representation of th
e W_3-algebra is strongly local.\nFor central charge c>2\, this yields a n
ew conformal net. We further prove\nthat these nets do not satisfy strong
additivity\, and hence are not\ncompletely rational.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nils Carqueville (Universität Wien)
DTSTART:20211111T151000Z
DTEND:20211111T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/22
DESCRIPTION:Title: Fully extended spin TQFTs\nby Nils Carqueville (Universitä
t Wien) as part of Online GAPT Seminar\n\nLecture held in BigBlueButton.\n
\nAbstract\nI shall discuss topological quantum field theories on 2-dimens
ional bordisms with spin structures. After reviewing the functorial approa
ch by Atiyah and Segal\, I will explain what it means for TQFTs to be "ext
ended to the point". The general theory will be illustrated by and applied
to state sum models\, Landau-Ginzburg models\, and truncated 3-dimensiona
l sigma models. \n\n(Based on joint work with Lóránt Szegedy\, and with
Ilka Brunner and \nDaniel Roggenkamp.)\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Federico Barbacovi (University College London)
DTSTART:20211118T151000Z
DTEND:20211118T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/23
DESCRIPTION:Title: Categorical dynamics\nby Federico Barbacovi (University Col
lege London) as part of Online GAPT Seminar\n\n\nAbstract\nA topological d
ynamical 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 ca
lled the topological entropy of $f$\, which is a non-negative extended rea
l number. A famous theorem of Gromov and Yomdin says that when $X$ is a sm
ooth\, projective variety\, and $f$ is a holomorphic automorphism\, the to
pological entropy of $f$ can be computed by looking at the action of $f$ o
n the (algebraic part of the) cohomology. For the derived-category-minded
geometer\, it is therefore natural to ask whether such result is the shado
w of some statement that holds at the level of derived categories.\nIn thi
s talk I will introduce the notion of categorical dynamical system as defi
ned by Dimitrov-Haiden-Katzarkov-Kontsevich and I will report on joint wor
k with Jongmyeong Kim in which we tackle Kikuta-Takahashi’s conjecture (
which will be introduced during the talk) both in the negative direction (
producing new counterexamples) and positive direction (giving condition th
at ensure that it holds - at least in a weak sense).\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Penneys (The Ohio State University)
DTSTART:20211202T151000Z
DTEND:20211202T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/25
DESCRIPTION:Title: Fusion categories in mathematics and physics\nby David Penn
eys (The Ohio State University) as part of Online GAPT Seminar\n\n\nAbstra
ct\nClassically\, the notion of symmetry is described by a group. In recen
t decades\, we have seen the emergence of quantum mathematical objects who
se symmetries are best described by tensor categories. Fusion categories s
imultaneously generalize the notion of a finite group and its category of
finite dimensional complex representations\, and we think of these objects
as encoding quantum symmetries. We will give a basic introduction to the
theory of fusion categories and describe applications to some areas of mat
hematics and physics\, namely operator algebras and theoretical condensed
matter.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Corey Jones (North Carolina State University)
DTSTART:20211209T151000Z
DTEND:20211209T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/26
DESCRIPTION:Title: Braided tensor categories from von Neumann algebras\nby Cor
ey Jones (North Carolina State University) as part of Online GAPT Seminar\
n\n\nAbstract\nIn the setting of algebraic quantum field theory\, the supe
rselection sectors of a net of von Neumann algebras naturally form a braid
ed tensor category. In this talk we will explain an analogous constructi
on which assigns a braided tensor category to a single von Neumann algebra
\, despite the absence of spatial degrees of freedom. Our construction bui
lds on the work of Connes\, Jones and Popa\, and extends Connes' $\\chi(M)
$ invariant. We will highlight several parallels to the theory of conforma
l nets\, and show that for any finite depth inclusion $N\\subseteq M$ of n
on-Gamma $II_1$ factors\, the braided tensor category associated to the en
veloping algebra $M_{\\infty}$ is the Drinfeld center of the original stan
dard invariant.\n\nBased on joint work with Quan Chen and David Penneys.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christian Hagendorf (Université catholique de Louvain)
DTSTART:20211216T151000Z
DTEND:20211216T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/27
DESCRIPTION:Title: talk postponed\nby Christian Hagendorf (Université catholi
que de Louvain) as part of Online GAPT Seminar\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Magdalena Musat (Københavns Universitet)
DTSTART:20220217T151000Z
DTEND:20220217T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/28
DESCRIPTION:Title: On the convex structure of unital quantum channels\, factorizab
ility and the Connes Embedding Problem\nby Magdalena Musat (København
s Universitet) as part of Online GAPT Seminar\n\n\nAbstract\nFactorizable
quantum channels\, introduced by C. Anantharaman-Delaroche within the fra
mework of operator algebras\, have recently found important applications i
n the analysis of quantum information theory\, revealing new infinite dime
nsional phenomena\, and leading also to reformulations of the celebrated C
onnes Embedding Problem. In recent work with M. Rørdam\, we show that (i
nfinite dimensional) von Neumann algebras are\, indeed\, needed to describ
e such channels. Along the way\, I will explain some of the several facets
of the Connes Embedding Problem\, with particular emphasis on the related
interplay between operator algebras and quantum information theory.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christian Hagendorf (Université catholique de Louvain)
DTSTART:20220224T151000Z
DTEND:20220224T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/29
DESCRIPTION:Title: The supersymmetric eight-vertex model\nby Christian Hagendo
rf (Université catholique de Louvain) as part of Online GAPT Seminar\n\n\
nAbstract\nThe topic of this talk is the eight-vertex model on the square
lattice. We consider this model at its so-called "supersymmetric" or "comb
inatorial point"\, where it presents surprising links to supersymmetry\, e
numerative combinatorics and special functions. To illustrate these links\
, we discuss the model's transfer matrix. Its largest eigenvalue has a par
ticularly simple form in the case of an odd number of vertical lines and p
eriodic boundary conditions along the horizontal direction. We show that s
everal properties of the corresponding eigenvectors can be expressed in te
rms of special polynomials introduced by Rosengren\, Zinn-Justin\, and rec
ently related to the enumeration of three-colourings of the square lattice
by Hietala.\n\nThis talk is based on joint work with Jean Liénardy and S
andrine Brasseur and ongoing work with Hjalmar Rosengren.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anne-Laure Thiel (University of Caen)
DTSTART:20220310T151000Z
DTEND:20220310T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/30
DESCRIPTION:Title: A Soergel category for cyclic groups\nby Anne-Laure Thiel (
University of Caen) as part of Online GAPT Seminar\n\n\nAbstract\nThe cate
gory of Soergel bimodules plays an essential role in (higher) representati
on theory\, to construct categorical braid group actions and homological i
nvariants of knots. After having briefly recalled the definition and some
facts about this category\, the aim of this talk will be to present some o
f its generalizations. I will focus on a Soergel-like category attached to
a cyclic group. I will give a complete description of this category throu
gh a classification of its indecomposable objects and study its split Grot
hendieck ring. This gives rise to an algebra which is an extension of the
Hecke algebra of the cyclic group\, that can be presented by generators an
d relations. If time permits\, I will mention some partial results about a
diagrammatic description of this category: how Catalan numbers appear in
this context and how the Temperley-Lieb algebra can describe certain morph
ism spaces in this category. This is joint work with Thomas Gobet.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luca Pol (Universität Regensburg)
DTSTART:20220317T151000Z
DTEND:20220317T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/31
DESCRIPTION:Title: Torsion model for tensor-triangulated categories\nby Luca P
ol (Universität Regensburg) as part of Online GAPT Seminar\n\n\nAbstract\
nIn this talk I will discuss how one can construct a model for (sufficient
ly well-behaved) tensor triangulated categories built from the data of loc
al and torsion objects. The idea is to mirror constructions in commutative
algebra such as torsion and localization at prime ideals. I will then dis
cuss two interesting examples arising from algebra and equivariant stable
homotopy theory. This is joint work with S. Balchin\, J.P.C. Greenlees and
J. Williamson.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emily Norton (University of Kent)
DTSTART:20220324T151000Z
DTEND:20220324T160000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/32
DESCRIPTION:Title: Calibrated representations of cyclotomic Hecke algebras at root
s of unity\nby Emily Norton (University of Kent) as part of Online GAP
T Seminar\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 collection of parameters\, and its combinatorics involves multipartitio
ns instead of partitions. We are interested in the case when the parameter
s are roots of unity. In general\, we cannot hope for closed-form characte
r formulas of the irreducible representations. However\, a certain type of
representation called "calibrated" is more tractable: those representatio
ns on which the Jucys-Murphy elements act semisimply. We classify the cali
brated representations in terms of their Young diagrams\, give a multiplic
ity-free formula for their characters\, and homologically construct them v
ia BGG resolutions. This is joint work with Chris Bowman and José Simen
tal.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ramona Wolf (ETH Zürich)
DTSTART:20220331T141000Z
DTEND:20220331T150000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/33
DESCRIPTION:Title: From subfactors to conformal field theories via lattice models<
/a>\nby Ramona Wolf (ETH Zürich) as part of Online GAPT Seminar\n\n\nAbst
ract\nThere is a long-standing conjecture that to every subfactor\, there
exists a corresponding conformal field theory. Although a considerable amo
unt of evidence has been collected to support this conjecture\, the genera
l statement has not yet been proven or disproven. In the study of this cor
respondence\, it might be helpful to lend methods from physics: Since ever
y subfactors gives rise to two (unitary) fusion categories\, one can imagi
ne attempting to construct counterpart CFTs via lattice models built direc
tly from these categories. In this talk\, I will explain how this construc
tion works and discuss problems and challenges that occur when carrying it
out for relevant examples.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anne-Sophie Kaloghiros (Brunel University London)
DTSTART:20220505T141000Z
DTEND:20220505T150000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/34
DESCRIPTION:Title: 1-dimensional K-moduli spaces of Fano 3-folds\nby Anne-Soph
ie Kaloghiros (Brunel University London) as part of Online GAPT Seminar\n\
n\nAbstract\nRecent advances in the study of K-stability have shown that t
here is a projective good moduli space of K-polystable Q-Gorenstein smooth
able Q-Fano varieties of dimension n and volume V.\n\nThe classification o
f smooth 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 in
formation on the geometry of\nFano 3-folds. Fano 3-folds offer a rich sour
ce of examples in which we can explicitly construct and understand some K-
moduli spaces.\n\nIn this talk\, I will discuss some examples of 1-dimensi
onal K-moduli spaces of Fano 3-folds.\n\nThis is joint work with Abban\, C
heltsov\, Jiao\, Martinez-Garcia\, Papazachariou and Sarikyan.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simona Paoli (University of Aberdeen)
DTSTART:20220512T141000Z
DTEND:20220512T150000Z
DTSTAMP:20260404T094701Z
UID:OnlineGAPT/35
DESCRIPTION:Title: From Homotopy Theory to Higher categories\nby Simona Paoli
(University of Aberdeen) as part of Online GAPT Seminar\n\n\nAbstract\nTop
ological spaces can be studied by breaking them into building blocks\, cal
led $n$-types\, using a classical construction in homotopy theory\, the Po
stnikov decomposition. The desire to model algebraically the building bloc
ks of spaces was one of the motivations for the development of higher grou
poids\, generalizing the fundamental groupoid of a space. In this talk I w
ill first illustrate how this naturally leads to the need to encode weakly
associative and weakly unital compositions of higher morphisms in a highe
r groupoid and I will discuss the challenges that this poses.\n\nMore gene
rally\, structures arising in mathematical physics\, namely topological qu
antum field theories\, call for the need to define a notion of higher cate
gory\, in which higher morphisms are not necessarily invertible.\n\nThe pr
ecise formalization of the notions of higher groupoids and higher categori
es can be achieved through several combinatorial machineries. I will intro
duce one of the approaches arising from homotopy theory\, based on the not
ion of multisimplicial sets. I will finally briefly discuss why this appro
ach is promising in terms of proving a long-standing open conjecture in hi
gher category theory.\n
LOCATION:https://stable.researchseminars.org/talk/OnlineGAPT/35/
END:VEVENT
END:VCALENDAR