BEGIN:VCALENDAR
VERSION:2.0
PRODID:researchseminars.org
CALSCALE:GREGORIAN
X-WR-CALNAME:researchseminars.org
BEGIN:VEVENT
SUMMARY:Alessandro Sisto (Heriot-Watt U.)
DTSTART:20200930T190000Z
DTEND:20200930T200000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/1
DESCRIPTION:Title: (Hierarchically) hyperbolic quotients of mapping class groups\nby Alessandro Sisto (Heriot-Watt U.) as part of Heriot-Watt algebra\,
geometry and topology seminar (MAXIMALS)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jean Pierre Mutanguha (Max Planck Institute\, Bonn)
DTSTART:20201007T140000Z
DTEND:20201007T150000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/6
DESCRIPTION:Title: Finding relative immersions of free groups\nby Jean Pierre
Mutanguha (Max Planck Institute\, Bonn) as part of Heriot-Watt algebra\, g
eometry and topology seminar (MAXIMALS)\n\n\nAbstract\nThe overarching goa
l of train track theory of free group automorphism is finding the "best" w
ays to represent an automorphism so as to read off its dynamical propertie
s. In this talk I will describe the progress I made in developing the theo
ry for injective endomorphisms. To some degree\, it turns out nonsurjectiv
e endomorphisms have simpler dynamics -- a result that I found surprising.
\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Naomi Andrew (Southampton)
DTSTART:20201028T150000Z
DTEND:20201028T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/7
DESCRIPTION:Title: Free-by-cyclic groups and their automorphisms\nby Naomi And
rew (Southampton) as part of Heriot-Watt algebra\, geometry and topology s
eminar (MAXIMALS)\n\n\nAbstract\nFree-by-cyclic groups are\, on the face o
f it\, a fairly nice kind of semidirect product. They are determined by an
automorphism of a free group\, though\, so perhaps it shouldn't be a surp
rise that they can be hard to understand. We'll see how properties of the
defining automorphism (for example\, how lengths of words grow as it is it
erated) determine properties of these groups\, and in particular we'll loo
k at their outer automorphism groups\, by investigating their actions on t
rees. (This is joint work with Armando Martino.)\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicolaus Heuer (Oxford)
DTSTART:20201104T150000Z
DTEND:20201104T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/8
DESCRIPTION:Title: Stable commutator length on RAAGs\nby Nicolaus Heuer (Oxfor
d) as part of Heriot-Watt algebra\, geometry and topology seminar (MAXIMAL
S)\n\n\nAbstract\nThe stable commutator length scl(g) of an element g in a
group G measures the least complexity of a surface to “fill” g. Stabl
e commutator length on non-abelian free groups is now fairly well understo
od but some questions remain open: Which rational numbers arise as scls? W
hat is the distribution of scl for random elements? What is the gap for ch
ains of scl?\n\nI will give a partial answer to all of these questions for
right-angled Artin groups (RAAGs). If time permits\, I will also show tha
t computing scl in RAAGs is (unlike in free groups) NP-hard.\n\nThis is jo
int work with Lvzhou Chen.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Davide Spriano (Oxford)
DTSTART:20201118T150000Z
DTEND:20201118T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/9
DESCRIPTION:Title: Generalizing hyperbolicity via local-to-global behaviour
\nby Davide Spriano (Oxford) as part of Heriot-Watt algebra\, geometry and
topology seminar (MAXIMALS)\n\n\nAbstract\nAn important property of a Gro
mov hyperbolic space is that every path that is locally a quasi-geodesi
c is globally a quasi-geodesic. A theorem of Gromov states that this is
a characterization of hyperbolicity\, which means that all the properties
of hyperbolic spaces and groups can be traced back to this simple fact. I
n this talk we generalize this property by considering only Morse quasi-
geodesic. We show that not only this allows to consider a much larger
class of examples\, such as CAT(0) spaces\, hierarchically hyperbolic spac
es and fundamental groups of 3-manifolds\, but also to effortlessly gen
eralize several results from the theory of hyperbolic groups that were pre
viously unknown in this generality.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jean Fromentin (Université du Littoral Côte d'Opale)
DTSTART:20201209T150000Z
DTEND:20201209T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/10
DESCRIPTION:Title: Experimentation on growth series of braids groups\nby Jean
Fromentin (Université du Littoral Côte d'Opale) as part of Heriot-Watt
algebra\, geometry and topology seminar (MAXIMALS)\n\n\nAbstract\nWe intro
duce a new algorithmic framework to investigate spherical and geodesic gro
wth series of braid groups relatively to the Artin's or Birman--Ko--Lee's
generators. Our experimentations in the case of three and four strands all
ow us to conjecture rational expressions for the spherical growth series w
ith respect to the Birman--Ko--Lee's generators.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Laurent Bartholdi (Göttingen)
DTSTART:20201125T150000Z
DTEND:20201125T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/12
DESCRIPTION:Title: Dimension series and homotopy groups of spheres\nby Lauren
t Bartholdi (Göttingen) as part of Heriot-Watt algebra\, geometry and top
ology seminar (MAXIMALS)\n\n\nAbstract\nThe lower central series of a grou
p $G$ is defined by $\\gamma_1=G$ and $\\gamma_n = [G\,\\gamma_{n-1}]$. Th
e "dimension series"\, introduced by Magnus\, is defined using the group a
lgebra over the integers: $\\delta_n = \\{g: g-1\\text{ belongs to the $n$
-th power of the augmentation ideal}\\}$.\n\nIt has been\, for the last 80
years\, a fundamental problem of group theory to relate these two series.
One always has $\\delta_n\\ge\\gamma_n$\, and a conjecture by Magnus\, wi
th false proofs by Cohn\, Losey\, etc.\, claims that they coincide\; but R
ips constructed an example with $\\delta_4/\\gamma_4$ cyclic of order 2. O
n the positive side\, Sjogren showed that $\\delta_n/\\gamma_n$ is always
a torsion group\, of exponent bounded by a function of $n$. Furthermore\,
it was believed (and falsely proven by Gupta) that only $2$-torsion may oc
cur.\n\nIn joint work with Roman Mikhailov\, we prove however that for eve
ry prime $p$ there is a group with $p$-torsion in some quotient $\\delta_n
/\\gamma_n$.\n\nEven more interestingly\, I will show that the dimension q
uotient $\\delta_n/gamma_n$ is related to the difference between homotopy
and homology: our construction is fundamentally based on the order-$p$ ele
ment in the homotopy group $\\pi_{2p}(S^2)$ due to Serre.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicolas Vaskou (Heriot-Watt)
DTSTART:20201202T150000Z
DTEND:20201202T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/13
DESCRIPTION:Title: Acylindrical hyperbolicity for Artin groups of dimension 2
\nby Nicolas Vaskou (Heriot-Watt) as part of Heriot-Watt algebra\, geometr
y and topology seminar (MAXIMALS)\n\n\nAbstract\nIn this talk we will star
t by introducing the notion of Artin groups\, as well as the notion of acy
lindrical hyperbolicity. We will see how a large class of Artin groups\, n
amely the two-dimensional Artin groups\, satisfy the latter property\, in
the following sense :\n\nTheorem : Irreducible two-dimensional Artin grou
ps on at least three generators are acylindrically hyperbolic.\n\nIn order
to prove this Theorem\, we will look at the action of such Artin groups o
n their modified Deligne complex\, a two-dimensional simplicial complex th
at is naturally associated with them. The proof relies on using a variant
of the WPD condition introduced by [Martin]\, for which we will need to st
udy various algebraic and geometric properties of two-dimensional Artin gr
oups.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matthieu Calvez (Heriot-Watt U.)
DTSTART:20210120T150000Z
DTEND:20210120T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/14
DESCRIPTION:Title: Garside structures in Artin-Tits groups and acylindrical hyper
bolicity\nby Matthieu Calvez (Heriot-Watt U.) as part of Heriot-Watt a
lgebra\, geometry and topology seminar (MAXIMALS)\n\n\nAbstract\nI intend
to present succinctly the construction of the additional length graph asso
ciated to a Garside group. This is a hyperbolic graph on which the group a
cts by isometries. Under some mild conditions\, one can show that a Garsid
e group possesses some elements whose action on the additional length grap
h is Weakly Partially Discontinuous. This applies in particular to prove t
hat spherical and euclidean Artin-Tits groups are acylindrically hyperboli
c.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pallavi Dani (Louisiana State U.)
DTSTART:20210127T150000Z
DTEND:20210127T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/15
DESCRIPTION:Title: Subgroups of right-angled Coxeter groups via Stallings-like te
chniques\nby Pallavi Dani (Louisiana State U.) as part of Heriot-Watt
algebra\, geometry and topology seminar (MAXIMALS)\n\n\nAbstract\nStalling
s folds have been extremely influential in the study of subgroups of free
groups. I will describe joint work with Ivan Levcovitz\, in which we deve
lop an analogue for the setting of right-angled Coxeter groups\, and use i
t to prove structural and algorithmic results about their subgroups.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Agata Smoktunowicz (Edinburgh U.)
DTSTART:20210203T150000Z
DTEND:20210203T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/16
DESCRIPTION:Title: A review of research utilizing Rump’s notion of a brace\
nby Agata Smoktunowicz (Edinburgh U.) as part of Heriot-Watt algebra\, geo
metry and topology seminar (MAXIMALS)\n\n\nAbstract\nIn around 2005\, in a
(successful!) attempt to describe all involutive\, non-degenerate set t
heoretic solutions of the Yang-Baxter equation\, the notion of a brace was
introduced by Wolfgang Rump. This formulation then rapidly found applicat
ion in other research areas. This talk will review these applications. \n
\nDefinition. A set $A$ with binary operations of addition $+$\, and multi
plication $\\circ $ is a brace if $(A\; +)$ is an abelian group\, $(A\; \\
circ)$ is a group and $a\\circ (b+c)+a=a\\circ b+a\\circ c $ for every $
a\, b\, c\\in A$. It follows from this definition that every nilpotent rin
g with the usual addition and with multiplication $a\\circ b=ab+a+b$ is a
brace.\n\n Braces have been shown to be equivalent to several concepts in
group theory such as groups with bijective 1-cocycles\, regular subgroups
of the holomorph of abelian groups\, matched pairs of groups and Garside
Groups. There is a connection between braces and grupoids. In 2015\, Gatev
a-Ivanova showed that there is a correspondence between braces and braided
groups with an involutive braiding operator. \n\nThere is also a connecti
on between braces and pre-Lie algebras. One generator braces have been sho
w to describe indecomposable\, involutive solutions of the Yang-Baxter equ
ation.\n\nOn the other hand\, Anastasia Doikou and Robert Weston have rece
ntly found fascinating connections between braces and quantum integrable
systems. Solutions of the pentagon equation related to braces have recentl
y been investigated by several authors.\n\nWe will look at some of the abo
ve connections along with some results about braces.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Suraj Krishna M S (Tata Institute of Fundamental Research)
DTSTART:20210210T150000Z
DTEND:20210210T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/17
DESCRIPTION:Title: The mapping torus of a torsion-free hyperbolic group is relati
vely hyperbolic\nby Suraj Krishna M S (Tata Institute of Fundamental R
esearch) as part of Heriot-Watt algebra\, geometry and topology seminar (M
AXIMALS)\n\n\nAbstract\nAn important method of studying an automorphism $\
\alpha$ of a group $G$ is the mapping torus $G \\rtimes_{\\alpha} \\mathbb
{Z}$. In a celebrated result\, Thurston showed that if $G$ is the fundamen
tal group of a closed orientable surface of genus at least 2\, then its ma
pping torus is hyperbolic if and only if no power of $\\alpha$ preserves a
non-trivial conjugacy class. In this talk\, I will describe joint work wi
th François Dahmani\, where we show that if $G$ is torsion-free hyperboli
c\, then $G\\rtimes_{\\alpha} \\mathbb{Z}$ is relatively hyperbolic with "
optimal" parabolic subgroups.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marissa Miller (Illinois Urbana-Champaign)
DTSTART:20210224T150000Z
DTEND:20210224T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/19
DESCRIPTION:Title: Geometry of the genus two handlebody group\nby Marissa Mil
ler (Illinois Urbana-Champaign) as part of Heriot-Watt algebra\, geometry
and topology seminar (MAXIMALS)\n\n\nAbstract\nIn this talk\, we explore t
he geometry of the handlebody group\, i.e. the mapping class group of a ha
ndlebody. This talk will include a heuristic description of hierarchically
hyperbolic spaces\, and using this description\, we will see that the han
dlebody group of genus two is a hierarchically hyperbolic group (HHG). The
n\, by analyzing the structure of the maximal hyperbolic space associated
to the handlebody group and utilizing the characterization of stable subgr
oups of HHGs\, I will show that the stable subgroups of the genus two hand
lebody group are precisely those subgroups whose orbit maps are quasi-isom
etric embeddings into the disk graph. Lastly\, we will see that various pr
operties of the genus two handlebody group do not hold for higher genus ha
ndlebody groups.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:André Carvalho (U. Porto)
DTSTART:20210310T150000Z
DTEND:20210310T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/20
DESCRIPTION:Title: Endomorphisms of the direct product of two free groups\nby
André Carvalho (U. Porto) as part of Heriot-Watt algebra\, geometry and
topology seminar (MAXIMALS)\n\n\nAbstract\nIn this talk\, we will describe
the endomorphisms of the direct product of two free groups of finite rank
and show how this description can be used to solve the Whitehead problems
for endomorphisms\, monomorphisms and automorphisms. The structure of the
group of automorphisms for groups in this class will also be discussed an
d finiteness conditions on the fixed and periodic points subgroups will be
given. Finally\, we will briefly present some results on the dynamics of
a continuous extension of an endomorphism to the completion of the group w
hen a suitable metric is considered.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thomas Haettel (U. Montpellier)
DTSTART:20210317T150000Z
DTEND:20210317T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/21
DESCRIPTION:Title: Group actions on injective metric spaces\nby Thomas Haette
l (U. Montpellier) as part of Heriot-Watt algebra\, geometry and topology
seminar (MAXIMALS)\n\n\nAbstract\nWe will review isometric actions of grou
ps on injective metric spaces and Helly graphs\, which display nonpositive
curvature features. We will then present two recent applications. The fir
st one concerns hierarchically hyperbolic groups and mapping class groups\
, and this is joint work with Nima Hoda and Harry Petyt. The second one co
ncerns higher rank uniform lattices in semisimple Lie groups and some Arti
n groups.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rylee Lyman (Rutgers)
DTSTART:20210303T133000Z
DTEND:20210303T143000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/22
DESCRIPTION:Title: Folding-like Techniques for CAT(0) Cube Complexes\nby Ryle
e Lyman (Rutgers) as part of Heriot-Watt algebra\, geometry and topology s
eminar (MAXIMALS)\n\n\nAbstract\nIn a seminal paper\, Stallings introduced
folding of morphisms of graphs\, giving effective\, algorithmic answers a
nd proofs to classical questions about subgroups of free groups. Recently
Dani and Levcovitz used Stallings-like methods to study right-angled Coxet
er groups\, which act geometrically on CAT(0) cube complexes. With Michael
Ben-Zvi and Robert Kropholler\, I extend their techniques to fundamental
groups of non-positively curved cube complexes. In this talk I will recall
Stallings's folds\, describe how to extend them to non-positively curved
cube complexes and discuss some applications.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vaibhav Gadre (U. Glasgow)
DTSTART:20210421T140000Z
DTEND:20210421T150000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/23
DESCRIPTION:Title: Statistical hyperbolicity of Teichmuller spaces\nby Vaibha
v Gadre (U. Glasgow) as part of Heriot-Watt algebra\, geometry and topolog
y seminar (MAXIMALS)\n\n\nAbstract\nThe notion of statistical hyperbolicit
y\, introduced by Duchin-Lelievre- Mooney\, encapsulates whether a space i
s hyperbolic "on average". More precisely\, a metric space is said to be s
tatistically hyperbolic if the average distance between a pair of points o
n a large sphere of radius R approaches 2R as the radius R approaches infi
nity. While Teichmuller spaces are not hyperbolic in the traditional sense
of Gromov\, we show that they are statistically hyperbolic for a large cl
ass of natural measures\, including the Lebesgue class measures for which
statistical hyperbolicity is known by the work of Dowdall-Duchin-Masur. T
his is joint work with Luke Jeffreys and Aitor Azemar.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Charles Cox (U. Bristol)
DTSTART:20210428T140000Z
DTEND:20210428T150000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/24
DESCRIPTION:Title: Spread and infinite groups\nby Charles Cox (U. Bristol) as
part of Heriot-Watt algebra\, geometry and topology seminar (MAXIMALS)\n\
n\nAbstract\nMy recent work has involved taking questions asked for finite
groups and considering them for infinite groups. There are various natura
l directions with this. In finite group theory\, there exist many beautifu
l results regarding generation properties. One such notion is that of spre
ad\, and Scott Harper and Casey Donoven have raised several intriguing que
stions for spread for infinite groups (in https://arxiv.org/abs/1907.05498
). A group $G$ has spread $k$ if for every $g_1\, \\dots\, g_k \\in G$ we
can find an $h \\in G$ such that $\\langle g_i\, h \\rangle = G$. For any
group we can say that if it has a proper quotient that is non-cyclic\, the
n it has spread 0. In the finite world there is then the astounding result
- which is the work of many authors - that this condition on proper quoti
ents is not just a necessary condition for positive spread\, but is also a
sufficient one. Harper-Donoven’s first question is therefore: is this t
he case for infinite groups? Well\, no. But that’s for the trivial reaso
n that we have infinite simple groups that are not 2-generated (and they p
oint out that 3-generated examples are also known). But if we restrict our
selves to 2-generated groups\, what happens? In this talk we’ll see the
answer to this question. The arguments will be concrete (*) and accessible
to a general audience.\n\n(*) at the risk of ruining the punchline\, we w
ill find a 2-generated group that has every proper quotient cyclic but tha
t has spread zero.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Enric Ventura (U. Politècnica de Catalunya)
DTSTART:20210505T140000Z
DTEND:20210505T150000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/25
DESCRIPTION:Title: Relative order and spectrum of subgroups\nby Enric Ventura
(U. Politècnica de Catalunya) as part of Heriot-Watt algebra\, geometry
and topology seminar (MAXIMALS)\n\n\nAbstract\nWe consider a natural gener
alization of the concept of order of a (torsion) element: the order of $g\
\in G$ relative to a subgroup $H\\leq G$ is the minimal $k>0$ such that $g
^k\\in H$\; and the spectrum of $H$ is defined as the set of orders of ele
ments from $G$ relative to $H$. After analyzing the first general properti
es of these concepts\, we obtain the following results: (1) every set of n
atural numbers closed under divisors\, is realizable as the spectrum of a
finitely generated subgroup $H$ of a finitely generated torsion-free group
$G$\; (2) $F_n\\times F_n$ has undecidable spectrum membership problem: t
here is no algorithm to decide\, given a finitely generated subgroup $H$ a
nd a natural number $k$\, whether $k$ belongs to the spectrum of $H$\; and
(3): in free groups F_n (as well as in free-times-free-abelian groups $F_
n\\times Z^m$) spectrum membership is solvable\, and one can give an expli
cit algorithmic-friendly description of the set of elements of a given ord
er $k$ relative to a given finitely generated subgroup $H$. \n(joint work
with J. Delgado and A. Zakarov)\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ric Wade (U. Oxford)
DTSTART:20210512T140000Z
DTEND:20210512T150000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/26
DESCRIPTION:Title: Rigidity following Ivanov in Aut(F_n) and Out(F_n)\nby Ric
Wade (U. Oxford) as part of Heriot-Watt algebra\, geometry and topology s
eminar (MAXIMALS)\n\n\nAbstract\nFollowing Ivanov\, there is a rich histor
y of proving algebraic and geometric rigidity results for mapping class gr
oups using combinatorial rigidity of the curve graph (and variations on th
is). We will outline some of this history and some key ideas\, before talk
ing about how we have been using Ivanov’s approach to study maps between
subgroups of $\\operatorname{Out}(F_n)$ (in work with Sebastian Hensel an
d Camille Horbez) and commensurations of $\\operatorname{Aut}(F_n)$ (in fo
rthcoming work with Martin Bridson). Some motivating related questions tha
t we can talk about are: “What does rigidity even mean?”\, “What is
the curve complex for $\\operatorname{Out}(F_n)$?” and “What is the di
fference between studying $\\operatorname{Out}(G)$ and $\\operatorname{Aut
}(G)$ for a group $G$?”\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Robert Kropholler (Münster)
DTSTART:20210623T140000Z
DTEND:20210623T150000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/27
DESCRIPTION:Title: Coarse embeddings and homological filling functions\nby Ro
bert Kropholler (Münster) as part of Heriot-Watt algebra\, geometry and t
opology seminar (MAXIMALS)\n\n\nAbstract\nThe homological filling function
of a finitely presented group $G$ measures the difficulty of filling loop
s with surfaces in a classifying space. The behaviour of this function whe
n passing to finitely presented subgroups is rather wild. If one adds assu
mptions on the dimension of $G$\, then one can bound the homological filli
ng function of the subgroup by that of $G$. I will discuss recent work wit
h Mark Pengitore generalising these results from subgroups to coarse embed
dings and also to higher dimensional filling functions.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Valentina Disarlo (Heidelberg)
DTSTART:20210630T140000Z
DTEND:20210630T150000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/28
DESCRIPTION:Title: The model theory of the curve graph\nby Valentina Disarlo
(Heidelberg) as part of Heriot-Watt algebra\, geometry and topology semina
r (MAXIMALS)\n\n\nAbstract\nI will discuss joint work with Javier de la Nu
ez Gonzalez (Bilbao) and Thomas Koberda (Virginia) in which we study the c
urve graph from the point of view of model theory. I will prove that the t
heory of the curve graph is ω--stable\, give bounds on its Morley rank\,
and show that it has quantifier elimination with respect to the class of
∃--formulae. I will also show that many of the complexes naturally assoc
iated to a surface are interpretable in the curve graph\, which proves tha
t these complexes are all ω--stable and admit certain a priori bounds on
their Morley ranks. I will address the notion of (bi)-interpretability\, w
hich allows to compare the logic of theories in different languages\, and
potential strategies for finding obstructions to the mutual (bi)-interpret
ability of different geometric complexes. This could provide a model theor
etical frame for Ivanov's metaconjecture.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alex Bishop (U. Sydney)
DTSTART:20211020T140000Z
DTEND:20211020T150000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/29
DESCRIPTION:Title: Towards a classification of geodesic growth in groups\nby
Alex Bishop (U. Sydney) as part of Heriot-Watt algebra\, geometry and topo
logy seminar (MAXIMALS)\n\n\nAbstract\nOne of the most well-known results
in geometric group theory is Gromov theorem which completely classifies th
e groups with polynomial volume growth. Bridson\, Burillo\, Elder and Šun
ić (2012) asked if such a classification exists for geodesic growth. In t
his talk\, we take steps towards such a classification by providing a nice
characterisation of the geodesic growth for virtually abelian groups\, an
d the first example of a virtually 2-step nilpotent group with polynomial
geodesic growth where previously the only virtually abelian examples were
known.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Martín Blufstein (Buenos Aires)
DTSTART:20211027T140000Z
DTEND:20211027T150000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/30
DESCRIPTION:Title: Parabolic subgroups of two-dimensional Artin groups\nby Ma
rtín Blufstein (Buenos Aires) as part of Heriot-Watt algebra\, geometry a
nd topology seminar (MAXIMALS)\n\n\nAbstract\nParabolic subgroups are esse
ntial in the study of Artin groups. The question of whether the intersecti
on of parabolic subgroups of any Artin group is a parabolic subgroup is st
ill open\, but the answer is known in some cases. A recent article by Cump
lido\, Martin and Vaskou introduces a geometric strategy for approaching t
his question. In this talk we will show how to use this strategy to study
the question in the two-dimensional case. To do so\, we will introduce sys
tolic-by-function complexes\, which are a generalization of systolic compl
exes.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chloé Papin (Université Grenoble-Alpes)
DTSTART:20211110T150000Z
DTEND:20211110T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/31
DESCRIPTION:Title: A Whitehead algorithm for Generalized Baumslag-Solitar groups<
/a>\nby Chloé Papin (Université Grenoble-Alpes) as part of Heriot-Watt a
lgebra\, geometry and topology seminar (MAXIMALS)\n\n\nAbstract\nBaumslag-
Solitar groups $BS(p\,q) =\\langle a\, t | ta^p t^{-1} = a^q \\rangle$ wer
e first introduced as examples of non-Hopfian groups. They may be describe
d using graphs of cyclic groups. In analogy with the study of $Out(F_N)$ o
ne can study their automorphisms through their action on an "outer space".
After introducing generalized Baumslag-Solitar groups and their actions o
n trees\, I will present an analogue of a Whitehead algorithm which takes
an element of a free group and decides whether there exists a free factor
which contains that element.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jennifer Taback (Bowdoin College)
DTSTART:20211117T150000Z
DTEND:20211117T160000Z
DTSTAMP:20260404T111108Z
UID:HW_MAXIMALS/32
DESCRIPTION:Title: A new proof of the growth rate of the solvable Baumslag-Solita
r groups\nby Jennifer Taback (Bowdoin College) as part of Heriot-Watt
algebra\, geometry and topology seminar (MAXIMALS)\n\n\nAbstract\nI will d
escribe a new proof of the growth rate of the solvable Baumslag-Solitar gr
oups BS(1\,n)\, which was originally computed by Collins\, Edjvet and Gill
in 1994. In joint work with Alden Walker\, we exhibit a regular language
of geodesics for a large set of elements in BS(1\,n) and show that the gr
owth rate of this language is the same as the growth rate of the group. W
e developed these methods and ways of describing geodesic paths in $BS(1\,
n)$ in order to understand conjugation curvature\, as introduced by Bar-Na
tan\, Duchin and Kropholler\, for these groups.\n
LOCATION:https://stable.researchseminars.org/talk/HW_MAXIMALS/32/
END:VEVENT
END:VCALENDAR