BEGIN:VCALENDAR
VERSION:2.0
PRODID:researchseminars.org
CALSCALE:GREGORIAN
X-WR-CALNAME:researchseminars.org
BEGIN:VEVENT
SUMMARY:Elia Fioravanti (MPIM-Bonn)
DTSTART;VALUE=DATE-TIME:20211019T130000Z
DTEND;VALUE=DATE-TIME:20211019T150000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/1
DESCRIPTION:Title: Automorphisms and splittings of special groups\nby Elia Fioravanti (M
PIM-Bonn) as part of Vienna Geometry and Analysis on Groups Seminar\n\n\nA
bstract\nThe automorphism group of a discrete group \\(G\\) can often be d
escribed quite explicitly in terms of the amalgamated-product and HNN spli
ttings of \\(G\\) over a family of subgroups. In the introductory talk\, I
will discuss the classical case when \\(G\\) is a Gromov-hyperbolic group
(originally due to Rips and Sela)\, highlighting some of the techniques i
nvolved. The research talk will then focus on automorphisms of 'special gr
oups'\, a broad family of subgroups of right-angled Artin groups introduce
d by Haglund and Wise. The main result is that\, when \\(G\\) is special\,
the outer automorphism group \\(\\mathrm{Out}(G)\\) is infinite if and on
ly if \\(G\\) splits over a centraliser or closely related subgroups. A si
milar result holds for automorphisms that preserve a coarse median structu
re on \\(G\\).\n
LOCATION:https://researchseminars.org/talk/WienGAGT/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Greg Bell (UNC Greensboro)
DTSTART;VALUE=DATE-TIME:20211109T140000Z
DTEND;VALUE=DATE-TIME:20211109T160000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/2
DESCRIPTION:Title: Property A and duality in linear programming\nby Greg Bell (UNC Green
sboro) as part of Vienna Geometry and Analysis on Groups Seminar\n\n\nAbst
ract\nYu introduced property A in 2000 in his work on the Novikov conjectu
re as a means to guarantee a uniform embedding into Hilbert space. The cla
ss of groups and metric spaces with property A is vast and includes spaces
with finite asymptotic dimension or finite decomposition complexity\, amo
ng others. We reduce property A to a sequence of linear programming optimi
zation problems on finite graphs. We explore the dual problem\, which prov
ides a means to show that a graph fails to have property A. As consequence
s\, we examine the difference between graphs with expanders and graphs wit
hout property A\, we recover theorems of Willett and Nowak concerning grap
hs without property A\, and arrive at a natural notion of mean property A.
This is joint work with Andrzej Nagórko\, University of Warsaw.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sahana Balasubramanya (Münster)
DTSTART;VALUE=DATE-TIME:20211116T140000Z
DTEND;VALUE=DATE-TIME:20211116T160000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/3
DESCRIPTION:Title: Actions of solvable groups on hyperbolic spaces\nby Sahana Balasubram
anya (Münster) as part of Vienna Geometry and Analysis on Groups Seminar\
n\n\nAbstract\nRecent papers of Balasubramanya and Abbott-Rasmussen have c
lassified the hyperbolic actions of several families of classically studie
d solvable groups. A key tool for these investigations is the machinery of
confining subsets of Caprace-Cornulier-Monod-Tessera. This machinery appl
ies in particular to solvable groups with virtually cyclic abelianizations
.\n\nIn this talk\, my goal is to explain how to extend this machinery to
classify the hyperbolic actions of certain solvable groups with higher ran
k abelianizations. We apply this extension to classify the hyperbolic acti
ons of a family of groups related to Baumslag-Solitar groups.\n\nThe first
half of the talk will cover the required preliminary information and some
of the known results concerning the hyperbolic actions of certain solvabl
e groups. In the second half\, I shall explain the techniques used to pro
ve the aforementioned results. Lastly\, I shall talk about the new results
that we prove in our paper that generalize these techniques. \n\n (joint
work with A.Rasmussen and C.Abbott)\n
LOCATION:https://researchseminars.org/talk/WienGAGT/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jean Pierre Mutanguha (IAS)
DTSTART;VALUE=DATE-TIME:20211123T140000Z
DTEND;VALUE=DATE-TIME:20211123T160000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/4
DESCRIPTION:Title: Limit pretrees for free group automorphisms\nby Jean Pierre Mutanguha
(IAS) as part of Vienna Geometry and Analysis on Groups Seminar\n\n\nAbst
ract\nFree group automorphisms seem to share a lot with surface homeomorph
isms. While tools for studying mapping class groups do not always have cou
nterparts in the free group setting\, it has nevertheless been extremely f
ruitful to mimic these tools as much as we can. This talk will describe ou
r attempt to develop one important missing analogue. Nielsen--Thurston the
ory gives a canonical representation of a surface homeomorphism's isotopy
class. Currently\, no such canonical representation of free group outer au
tomorphisms exists. \n\nIn the introductory talk\, I will describe the Nie
lsen--Thurston theory in some detail and outline the proof of this canonic
al representation. For the research talk\, I will discuss the main obstacl
es to carrying out the same argument with free group automorphisms. Fortun
ately\, it appears these obstacles are surmountable and I will discuss som
e partial results in this direction.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matt Zaremsky (SUNY Albany)
DTSTART;VALUE=DATE-TIME:20211130T140000Z
DTEND;VALUE=DATE-TIME:20211130T160000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/5
DESCRIPTION:Title: Higher virtual algebraic fibering of certain right-angled Coxeter groups<
/a>\nby Matt Zaremsky (SUNY Albany) as part of Vienna Geometry and Analysi
s on Groups Seminar\n\n\nAbstract\nA group is said to "virtually algebraic
ally fiber" if it has a finite index subgroup admitting a map onto Z with
finitely generated kernel. Stronger than finite generation\, if the kernel
is even of type F_n for some n then we say the group "virtually algebraic
ally F_n-fibers". Right-angled Coxeter groups (RACGs) are a class of group
s for which the question of virtual algebraic F_n-fibering is of great int
erest. In joint work with Eduard Schesler\, we introduce a new probabilist
ic criterion for the defining flag complex that ensures a RACG virtually a
lgebraically F_n-fibers. This expands on work of Jankiewicz--Norin--Wise\,
who developed a way of applying Bestvina--Brady Morse theory to the Davis
complex of a RACG to deduce virtual algebraic fibering. We apply our crit
erion to the special case where the defining flag complex comes from a cer
tain family of finite buildings\, and establish virtual algebraic F_n-fibe
ring for such RACGs. The bulk of the work involves proving that a "random"
(in some sense) subcomplex of such a building is highly connected\, which
is interesting in its own right.\n\nIn the first half of the talk I will
focus just on what Jankiewicz--Norin--Wise did\, so in particular always n
=1\, and then in the second half I will get into the n>1 case and the spec
ific examples.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matt Cordes (ETH Zürich)
DTSTART;VALUE=DATE-TIME:20211207T140000Z
DTEND;VALUE=DATE-TIME:20211207T160000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/6
DESCRIPTION:Title: Coxeter groups with connected Morse boundary\nby Matt Cordes (ETH Zü
rich) as part of Vienna Geometry and Analysis on Groups Seminar\n\n\nAbstr
act\nThe Morse boundary is a quasi-isometry invariant that encodes the pos
sible "hyperbolic" directions of a group. The topology of the Morse bounda
ry can be challenging to understand\, even for simple examples. In this ta
lk\, I will focus on a basic topological property: connectivity and on a w
ell-studied class of CAT(0) groups: Coxeter groups. I will discuss a crite
ria that guarantees that the Morse boundary of a Coxeter group is connecte
d. In particular\, when we restrict to the right-angled case\, we get a fu
ll characterization of right-angled Coxeter groups with connected Morse bo
undary. This is joint work with Ivan Levcovitz.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Kerr (Münster)
DTSTART;VALUE=DATE-TIME:20220111T140000Z
DTEND;VALUE=DATE-TIME:20220111T160000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/7
DESCRIPTION:Title: Entropy\, orbit equivalence\, and sparse connectivity\nby David Kerr
(Münster) as part of Vienna Geometry and Analysis on Groups Seminar\n\n\n
Abstract\nIt was shown a few years ago by Tim Austin that if an orbit equi
valence between probability-measure-preserving actions of finitely generat
ed amenable groups is integrable then it preserves entropy. I will discuss
some joint work with Hanfeng Li in which we show that the same conclusion
holds for the maximal sofic entropy when the acting groups are countable
and sofic and contain an amenable w-normal subgroup which is not locally v
irtually cyclic\, and that it is moreover enough to assume that the Shanno
n entropy of the cocycle partitions is finite (what we call Shannon orbit
equivalence). One consequence is that two Bernoulli actions of a group in
the above class are Shannon orbit equivalent if and only if they are conju
gate.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Benjamin Steinberg (CUNY)
DTSTART;VALUE=DATE-TIME:20220118T140000Z
DTEND;VALUE=DATE-TIME:20220118T160000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/8
DESCRIPTION:Title: Simplicity of Nekrashevych algebras of contracting self-similar groups\nby Benjamin Steinberg (CUNY) as part of Vienna Geometry and Analysis on
Groups Seminar\n\n\nAbstract\nA self-similar group is a group $G$ acting
on the Cayley graph of a finitely generated free monoid $X^*$ (i.e.\, regu
lar rooted tree) by automorphisms in such a way that the self-similarity o
f the tree is reflected in the group. The most common examples are generat
ed by the states of a finite automaton. Many famous groups\, like Grigorch
uk's 2-group of intermediate growth are of this form. Nekrashevych associa
ted $C^*$-algebras and algebras with coefficients in a field to self-simil
ar groups. In the case $G$ is trivial\, the algebra is the classical Leavi
tt algebra\, a famous finitely presented simple algebra. Nekrashevych show
ed that the algebra associated to the Grigorchuk group is not simple in ch
aracteristic 2\, but Clark\, Exel\, Pardo\, Sims and Starling showed its N
ekrashevych algebra is simple over all other fields. Nekrashevych then sho
wed that the algebra associated to the Grigorchuk-Erschler group is not si
mple over any field (the first such example). The Grigorchuk and Grigorchu
k-Erschler groups are contracting self-similar groups. This important clas
s of self-similar groups includes Gupta-Sidki p-groups and many iterated m
onodromy groups like the Basilica group. Nekrashevych proved algebras asso
ciated to contacting groups are finitely presented.\n\nIn this talk we dis
cuss a recent result of the speaker and N. Szakacs (Manchester) characteri
zing simplicity of Nekrashevych algebras of contracting groups. In particu
lar\, we give an algorithm for deciding simplicity given an automaton gene
rating the group. We apply our results to several families of contracting
groups like Gupta-Sidki groups\, GGS groups and Sunic's generalizations of
Grigorchuk's group associated to polynomials over finite fields.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michele Triestino (Dijon)
DTSTART;VALUE=DATE-TIME:20220308T140000Z
DTEND;VALUE=DATE-TIME:20220308T160000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/9
DESCRIPTION:Title: Describing spaces of harmonic actions on the line\nby Michele Triesti
no (Dijon) as part of Vienna Geometry and Analysis on Groups Seminar\n\n\n
Abstract\nConsidering actions of a given group on a manifold can be seen a
s a nonlinear version of classical representation theory. In this context\
, there is a well-developed theory for actions on one-manifolds\, in contr
ast to the situation for higher-dimensional manifolds\, where the situatio
n is still at the level of exploration. This is mainly due to the tight re
lation to the theory of orderable groups\, which has no analogue in higher
dimension.\n\nHow to describe all possible actions on the line of a given
group? For finitely generated groups\, one can consider the space of harm
onic actions\, whose existence is based on a result of Deroin-Kleptsyn-Nav
as-Parwani. This turns out to be a compact space endowed with a translatio
n flow\, whose space of orbits gives exactly the space of all semi-conjuga
cy classes of actions on the line without global fixed points.\n\nWe are a
ble to understand the space of harmonic actions for solvable groups and ma
ny locally moving groups (including Thompson's F and generalizations): the
actions of these groups which are not the obvious ones\, are all obtained
from actions on planar real trees fixing a point at infinity. This talk i
s based on a joint project with J Brum\, N Matte Bon and C Rivas.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adrian Ioana (UCSD)
DTSTART;VALUE=DATE-TIME:20220315T140000Z
DTEND;VALUE=DATE-TIME:20220315T160000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/10
DESCRIPTION:Title: Almost commuting matrices and stability for product groups\nby Adria
n Ioana (UCSD) as part of Vienna Geometry and Analysis on Groups Seminar\n
\n\nAbstract\nI will present a result showing that the direct product grou
p \\(G=\\mathbb F_2\\times\\mathbb F_2\\)\, where \\(\\mathbb F_2\\) is th
e free group on two generators\, is not Hilbert-Schmidt stable. This means
that \\(G\\) admits a sequence of asymptotic homomorphisms (with respect
to the normalized Hilbert-Schmidt norm) which are not perturbations of gen
uine homomorphisms. While this result concerns unitary matrices\, its pro
of relies on techniques and ideas from the theory of von Neumann algebras.
I will also explain how this result can be used to settle in the negative
a natural version of an old question of Rosenthal concerning almost commu
ting matrices. More precisely\, we derive the existence of contraction mat
rices \\(A\,B\\) such that \\(A\\) almost commutes with \\(B\\) and \\(B^*
\\) (in the normalized Hilbert-Schmidt norm)\, but there are no matrices \
\(A’\,B’\\) close to \\(A\,B\\) such that \\(A’\\) commutes with \\(
B’\\) and \\(B’*\\).\n
LOCATION:https://researchseminars.org/talk/WienGAGT/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cameron Cinel (UCSD)
DTSTART;VALUE=DATE-TIME:20220322T140000Z
DTEND;VALUE=DATE-TIME:20220322T160000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/11
DESCRIPTION:Title: Sofic Lie Algebras\nby Cameron Cinel (UCSD) as part of Vienna Geomet
ry and Analysis on Groups Seminar\n\n\nAbstract\nWe introduce a notion of
soficity for Lie algebras\, similar to linear soficity for groups and asso
ciative algebras. Sofic Lie algebras can be thought of as Lie algebras tha
t locally are almost embeddable in \\(\\mathfrak{gl}_n(F)\\) for some \\(n
\\). We provide equivalent characterizations for soficity via metric ultra
products and local \\(\\varepsilon\\)-almost representations. We show that
Lie algebras of subexponential growth are sofic and give explicit familie
s of almost representations for specific Lie algebras. Finally we show tha
t\, over fields of characteristic 0\, a Lie algebra is sofic if and only i
f its universal enveloping algebra is linearly sofic.\n\n \n\n \n\nJoin Zo
om meeting ID 641 2123 2568 or via the link below. Passcode: A group is ca
lled an ________ group if it admits an invariant mean. (8 letters\, lowerc
ase)\n
LOCATION:https://researchseminars.org/talk/WienGAGT/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexandra Edletzberger (Vienna)
DTSTART;VALUE=DATE-TIME:20220329T130000Z
DTEND;VALUE=DATE-TIME:20220329T150000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/12
DESCRIPTION:Title: Quasi-Isometries for certain Right-Angled Coxeter Groups\nby Alexand
ra Edletzberger (Vienna) as part of Vienna Geometry and Analysis on Groups
Seminar\n\n\nAbstract\nWe will introduce a construction of a specific gra
ph of groups\, the so-called JSJ tree of cylinders\, for certain right-ang
led Coxeter groups (RACGs) in terms of the defining graph.\nWe will use th
is as a tool in the hunt for a solution to the Quasi-Isometry Problem of c
ertain RACGs\, because if there is a quasi-isometry between two RACGs\, th
ere is an induced tree isomorphism between the respective JSJ trees of cyl
inders. In particular\, this tree isomorphism preserves some additional st
ructure of the JSJ tree of cylinders. With this fact at hand we can distin
guish RACGs up to quasi-isometry.\nAdditionally\, we explain that in certa
in cases this structure preserving tree isomorphism even provides a comple
te quasi-isometry invariant.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Linton (Warwick)
DTSTART;VALUE=DATE-TIME:20220405T130000Z
DTEND;VALUE=DATE-TIME:20220405T150000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/13
DESCRIPTION:Title: Primitivity rank\, one-relator groups and hyperbolicity\nby Marco Li
nton (Warwick) as part of Vienna Geometry and Analysis on Groups Seminar\n
\n\nAbstract\nThe primitivity rank of an element \\(w\\) of a free group \
\(F\\) is defined as the minimal rank of a subgroup containing \\(w\\) as
an imprimitive element. Recent work of Louder and Wilton has shown that th
ere is a striking connection between this quantity and the subgroup struct
ure of the one-relator group \\(F/\\langle\\langle w\\rangle\\rangle\\). I
n this talk\, I will start by motivating the study of one-relator groups a
nd survey some recent advancements. Then\, I will show that one-relator gr
oups whose defining relation has primitivity rank at least 3 are hyperboli
c\, confirming a conjecture of Louder and Wilton. Finally\, I will discuss
the ingredients that go into proving this result.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emmanuel Breuillard (Oxford)
DTSTART;VALUE=DATE-TIME:20220426T130000Z
DTEND;VALUE=DATE-TIME:20220426T150000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/14
DESCRIPTION:Title: Random character varieties\nby Emmanuel Breuillard (Oxford) as part
of Vienna Geometry and Analysis on Groups Seminar\n\n\nAbstract\nConsider
a random group \\(\\Gamma\\) with \\(k\\) generators and \\(r\\) random re
lators of large length \\(N\\). We ask about the geometry of the character
variety of \\(\\Gamma\\) with values in \\(\\mathrm{SL}(2\,\\mathbb{C})\\
) or any semisimple Lie group \\(G\\). \nThis is the moduli space of group
homomorphisms from \\(\\Gamma\\) to \\(G\\) up to conjugation. \nWe show
that with an exponentially small proportion of exceptions the character va
riety is empty\, \\(k\\lt r+1\\)\, finite and large\, \\(k=r+1\\)\, or irr
educible of dimension \\((k-r-1) \\mathrm{dim}\\thinspace G\\)\, \\(k\\gt
r+1\\). The proofs use new results on expander graphs for finite simple gr
oups of Lie type and are conditional of the Riemann hypothesis.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Joseph Maher (CSI CUNY)
DTSTART;VALUE=DATE-TIME:20220503T130000Z
DTEND;VALUE=DATE-TIME:20220503T150000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/15
DESCRIPTION:Title: Random walks on WPD groups\nby Joseph Maher (CSI CUNY) as part of Vi
enna Geometry and Analysis on Groups Seminar\n\n\nAbstract\nWe'll introduc
e the WPD property for groups\, which can be thought of as a discreteness
property for the action of a group on a space which need not be locally co
mpact. More precisely\, the action of a group on a Gromov hyperbolic space
X is WPD if the action is coarsely discrete along the quasi-axis of a lox
odromic isometry. We'll give some examples of WPD groups\, which include t
he mapping class group of a surface and Out(F_n)\, and consider when the a
ction of a group on a quotient of X might still satisfy the WPD property.
We'll also show that WPD elements are generic for random walks on WPD gro
ups. This includes joint work with Hidetoshi Masai\, Saul Schleimer and Gi
ulio Tiozzo.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alessandro Sisto (Heriot-Watt)
DTSTART;VALUE=DATE-TIME:20220510T130000Z
DTEND;VALUE=DATE-TIME:20220510T150000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/16
DESCRIPTION:Title: Morse boundaries are sometimes not that wild\nby Alessandro Sisto (H
eriot-Watt) as part of Vienna Geometry and Analysis on Groups Seminar\n\n\
nAbstract\nThe Morse boundary of a metric space X is a topological space t
hat encodes the "hyperbolic directions" of X. When X is not hyperbolic\, i
ts Morse boundary is not even metrisable\, which makes it sound like it sh
ould be impossible to understand. As it turns out\, however\, there are va
rious results that describe the Morse boundaries of various interesting gr
oups\, some even giving complete descriptions of the homeomorphism type. T
he talk will be an overview of these results.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yves de Cornulier (Lyon)
DTSTART;VALUE=DATE-TIME:20220517T130000Z
DTEND;VALUE=DATE-TIME:20220517T150000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/17
DESCRIPTION:Title: Near group actions\nby Yves de Cornulier (Lyon) as part of Vienna Ge
ometry and Analysis on Groups Seminar\n\n\nAbstract\nFor a group action\,
every group element acts on a set as a permutation. We consider a similar
setting where each group element acts a permutation "modulo indeterminacy
on finite subsets". We will indicate various natural occurrences of near a
ctions. We will discuss realizability notions: is a given near action indu
ced by a genuine action?\n
LOCATION:https://researchseminars.org/talk/WienGAGT/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alex Evetts (Manchester)
DTSTART;VALUE=DATE-TIME:20220524T130000Z
DTEND;VALUE=DATE-TIME:20220524T150000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/18
DESCRIPTION:Title: Equations\, rational sets and formal languages\nby Alex Evetts (Manc
hester) as part of Vienna Geometry and Analysis on Groups Seminar\n\n\nAbs
tract\nThe set of solutions to a system of equations over a group is known
as an algebraic set. The study of such sets goes back to the 1970s and 19
80s and work of Makanin and Razborov. More recently\, there has been a sig
nificant amount of effort to describe algebraic sets in various classes of
groups using formal languages\, and in particular the class of EDT0L lang
uages. I will explain what an EDT0L language is and describe some recent r
esults on virtually abelian groups. Namely that their algebraic sets can b
e represented by EDT0L languages (joint work with A. Levine)\, and that th
e same is true for their rational sets\, those sets described by finite st
ate automata (joint work with L. Ciobanu).\n
LOCATION:https://researchseminars.org/talk/WienGAGT/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pallavi Dani (LSU)
DTSTART;VALUE=DATE-TIME:20220531T130000Z
DTEND;VALUE=DATE-TIME:20220531T150000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/19
DESCRIPTION:Title: Divergence\, thickness\, and hypergraph index for Coxeter groups\nby
Pallavi Dani (LSU) as part of Vienna Geometry and Analysis on Groups Semi
nar\n\nInteractive livestream: https://univienna.zoom.us/j/61386912732\nPa
ssword hint: A group is called an _____ group if it admits an invariant me
an.\n\nAbstract\nDivergence and thickness are well studied quasi-isometry
invariants for finitely generated groups. In general\, they can be quite
difficult to compute. In the case of right-angled Coxeter groups\, Levcov
itz introduced the notion of hypergraph index\, which can be algorithmical
ly computed from the defining graph\, and proved that it determines the th
ickness and divergence of the group. I will talk about joint work with Yu
sra Naqvi\, Ignat Soroko\, and Anne Thomas\, in which we propose a definit
ion of hypergraph index for general Coxeter groups. We show that it deter
mines the divergence and thickness in an infinite family of non-right-angl
ed Coxeter groups.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/19/
URL:https://univienna.zoom.us/j/61386912732
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sang-hyun Kim (KIAS)
DTSTART;VALUE=DATE-TIME:20220614T130000Z
DTEND;VALUE=DATE-TIME:20220614T150000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/20
DESCRIPTION:by Sang-hyun Kim (KIAS) as part of Vienna Geometry and Analysi
s on Groups Seminar\n\nInteractive livestream: https://univienna.zoom.us/j
/61386912732\nPassword hint: A group is called an _____ group if it admits
an invariant mean.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/WienGAGT/20/
URL:https://univienna.zoom.us/j/61386912732
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrés Navas (Santiago de Chile)
DTSTART;VALUE=DATE-TIME:20220628T130000Z
DTEND;VALUE=DATE-TIME:20220628T150000Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/21
DESCRIPTION:by Andrés Navas (Santiago de Chile) as part of Vienna Geometr
y and Analysis on Groups Seminar\n\nInteractive livestream: https://univie
nna.zoom.us/j/61386912732\nPassword hint: A group is called an _____ group
if it admits an invariant mean.\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/WienGAGT/21/
URL:https://univienna.zoom.us/j/61386912732
END:VEVENT
BEGIN:VEVENT
SUMMARY:Florin Radulescu (IMAR and Rome)
DTSTART;VALUE=DATE-TIME:20220602T100000Z
DTEND;VALUE=DATE-TIME:20220602T104500Z
DTSTAMP;VALUE=DATE-TIME:20220528T194639Z
UID:WienGAGT/22
DESCRIPTION:Title: Dimension formulae of Gelfand-Graev\, Jones and their relation to automo
rphic forms and temperdness of quasiregular representations\nby Florin
Radulescu (IMAR and Rome) as part of Vienna Geometry and Analysis on Grou
ps Seminar\n\nInteractive livestream: https://univienna.zoom.us/j/61386912
732\nPassword hint: A group is called an _____ group if it admits an invar
iant mean.\n\nAbstract\nVaughan Jones introduced a formula computing the v
on Neumann dimension for the restriction to a lattice of the left regular
representation of a semisimple Lie group.\n\nIt is a variant of a formula
by Atiah Schmidt computing the formal dimension in the Haris Chandra tra
ce formula for discrete series. It is surprisingly similar (in the case of
PSL(2\,Z)) to the dimension of the space of automorphic forms and is simi
lar to a formula proved by Gelfand\, Graev. We use an extension of this f
ormula to provide a method for computing the formal trace of representatio
ns of PSL(2\,Q_p) (or more general situations)\, when analyzing the quasi
regular representation on PSL(2\,R)/PSL(2\,Z). It provides a method to obt
ain estimates for eigenvalues of Hecke operators.\n
LOCATION:https://researchseminars.org/talk/WienGAGT/22/
URL:https://univienna.zoom.us/j/61386912732
END:VEVENT
END:VCALENDAR