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BEGIN:VEVENT
SUMMARY:Allison Moore (Virginia Commonwealth University)
DTSTART:20200908T180000Z
DTEND:20200908T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/1
DESCRIPTION:Title: Triple linking and Heegaard Floer homology.\nby Allison Moore
(Virginia Commonwealth University) as part of Brandeis Topology Seminar\n
\n\nAbstract\nWe will describe several appearances of Milnor’s invariant
s in the link Floer complex. This will include a formula that expresses th
e Milnor triple linking number in terms of the h-function. We will also sh
ow that the triple linking number is involved in a structural property of
the d-invariants of surgery on certain algebraically split links. We will
apply the above properties toward new detection results for the Borromean
and Whitehead links. This is joint work with Gorsky\, Lidman and Liu.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Abdul Zalloum (Queen's University)
DTSTART:20200915T180000Z
DTEND:20200915T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/2
DESCRIPTION:Title: Regularity of Morse geodesics and growth of stable subgroups\
nby Abdul Zalloum (Queen's University) as part of Brandeis Topology Semina
r\n\n\nAbstract\nThe study of groups with "hyperbolic-like directions" has
been a central theme in geometric group theory. Two notions are usually u
sed to quantify what is meant by "hyperbolic-like directions''\, the notio
n of a contracting geodesic and that of a Morse geodesic. Since the proper
ty that every geodesic ray in metric space X is contracting or Morse chara
cterizes hyperbolic spaces\, being a contracting/Morse geodesic is conside
red a hyperbolic-like property. In more general spaces\, the Morse propert
y is strictly weaker than the contracting property. However\, if one adds
an additional “local-to-global” condition on X\, then Morse geodesics
behave much like geodesics in hyperbolic spaces. Generalizing work of Ca
nnon\, I will first discuss a joint result with Eike proving that for any
finitely generated group\, the language of contracting geodesics with a fi
xed parameter is a regular language. I will then talk about recent work wi
th Cordes\, Russell and Spriano where we show that in local-to-global spac
es\, Morse geodesics also form a regular language\, and we give a characte
rization of stable subgroups in terms of regular languages.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ivan Levcovitz (Technion)
DTSTART:20200922T180000Z
DTEND:20200922T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/3
DESCRIPTION:Title: Characterizing divergence in right-angled Coxeter groups\nby
Ivan Levcovitz (Technion) as part of Brandeis Topology Seminar\n\n\nAbstra
ct\nA main goal in geometric group theory is to understand finitely genera
ted groups up to quasi-isometry (a coarse geometric equivalence relation o
n Cayley graphs). Right-angled Coxeter groups (RACGs) are a well-studied\,
wide class of groups whose coarse geometry is not well understood. One of
the few available quasi-isometry invariants known to distinguish non-rela
tively hyperbolic RACGs is the divergence function\, which roughly measure
s the maximum rate that a pair of geodesic rays in a Cayley graph can dive
rge from one another. In this talk I will discuss a recent result that com
pletely classifies divergence functions in RACGs\, gives a simple method o
f computing them and links divergence to other known quasi-isometry invari
ants.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ahmad Issa (University of British Columbia)
DTSTART:20200929T180000Z
DTEND:20200929T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/4
DESCRIPTION:by Ahmad Issa (University of British Columbia) as part of Bran
deis Topology Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Elia Fioravante (Max Planck Institute\, Bonn)
DTSTART:20201006T180000Z
DTEND:20201006T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/5
DESCRIPTION:Title: Cubulations determined by their length function\nby Elia Fior
avante (Max Planck Institute\, Bonn) as part of Brandeis Topology Seminar\
n\n\nAbstract\nThe theory of group actions on CAT(0) cube complexes has ex
erted a strong influence on geometric group theory and low-dimensional top
ology in the last two decades. Indeed\, knowing that a group G acts proper
ly and cocompactly on a CAT(0) cube complex reveals a lot of its algebraic
structure. However\, in general\, "cubulations" are non-canonical and the
group G can act on cube complexes in many different ways. It is thus natu
ral to attempt to classify all such actions for a fixed group G\, ideally
obtaining a good notion of "space of all cubulations of G". As a first ste
p\, we show that G-actions on CAT(0) cube complexes are often completely d
etermined by their length function. This yields a simple topology on this
space and a natural compactification resembling Thurston's compactificatio
n of Teichmüller space. Based on joint works with J. Beyrer and M. Hagen.
\n\nhttps://brandeis.zoom.us/j/99772088777\n\nPassword hint: negatively cu
rved (in algebra and geometry)\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Duncan (James Madison University)
DTSTART:20201013T180000Z
DTEND:20201013T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/6
DESCRIPTION:Title: Bundle splittings on boundary-punctured disks\nby David Dunca
n (James Madison University) as part of Brandeis Topology Seminar\n\n\nAbs
tract\nOver a Riemann surface\, a bundle pair is a holomorphic bundle toge
ther with a totally real subbundle on the boundary. A result of Oh states
that\, over a disk\, a bundle pair splits as a sum of line bundle pairs. W
e discuss work-in-progress that seeks to extend Oh's result to boundary-pu
nctured disks. The strategy is to use the Yang--Mills gradient flow for si
ngular connections to identify the relevant bundle isomorphism.\nhttps://b
randeis.zoom.us/j/99772088777\n\nPassword hint: negatively curved (in alge
bra and geometry)\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jonathan Simone (UMass Amherst)
DTSTART:20201020T180000Z
DTEND:20201020T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/7
DESCRIPTION:Title: Using rational homology circles to construct rational homology ba
lls\nby Jonathan Simone (UMass Amherst) as part of Brandeis Topology S
eminar\n\n\nAbstract\nMotivated by Akbulut-Larson's construction of Briesk
orn spheres bounding rational homology 4-balls\, we explore plumbed 3-mani
folds that bound rational homology circles and use them to construct infin
ite families of rational homology 3-spheres that bound rational homology 4
-balls. In particular\, we will classify torus bundles over the circle tha
t bound rational homology circles and provide a simple method for construc
ting more general plumbed 3-manifolds that bound rational homology circles
. We then use these rational homology circles to show that\, for example\,
-1-surgery along any twisted positively-clasped Whitehead double of any k
not bounds a rational homology 4-ball.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Amitesh Datta (Princeton University)
DTSTART:20201027T180000Z
DTEND:20201027T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/8
DESCRIPTION:Title: Is the braid group $B_4$ a group of $3\\times 3$-matrices?\nb
y Amitesh Datta (Princeton University) as part of Brandeis Topology Semina
r\n\n\nAbstract\nThe Burau representation is a classical linear representa
tion of the braid group that can be used to define the Alexander polynomia
l invariant for knots and links. \n\nThe question of whether or not the Bu
rau representation of the braid group $B_4$ is faithful is an open problem
since the 1930s. The faithfulness of this representation is necessary for
the Jones polynomial of a knot to detect the unknot.\n\nIn this talk\, I
will present my work on this problem\, which includes strong constraints o
n the kernel of this representation. The key techniques include a new inte
rpretation of the Burau matrix of a positive braid and a new decomposition
of positive braids into subproducts.\n\nI will discuss all of the relevan
t background for the problem from scratch and illustrate my techniques thr
ough simple examples. I will also highlight the beautiful and elegant conn
ections to bowling balls and quantum intersection numbers of simple closed
curves on punctured disks.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chris Scaduto (University of Miami)
DTSTART:20201103T190000Z
DTEND:20201103T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/9
DESCRIPTION:Title: Equivariant singular instanton homology\nby Chris Scaduto (Un
iversity of Miami) as part of Brandeis Topology Seminar\n\n\nAbstract\nEve
ry knot is the boundary of a normally immersed disk in the 4-ball. The 4D
clasp number of a knot is the minimal number of double points over all suc
h immersed disks. In this talk I will explain how certain equivariant coho
mological constructions in singular instanton Floer theory lead to new res
ults for 4D clasp numbers and unknotting numbers of knots. This is joint w
ork with Ali Daemi.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ceren Kose (UT Austin)
DTSTART:20201110T190000Z
DTEND:20201110T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/10
DESCRIPTION:Title: Composite Knots with Symmetric Union Presentations\nby Ceren
Kose (UT Austin) as part of Brandeis Topology Seminar\n\n\nAbstract\nAbst
ract: A symmetric union of\n a knot is an aesthetically appealing construc
tion which generalizes the connected sum of a knot and its mirror. As the
connected sum of a knot and its mirror is always ribbon\, hence smoothly s
lice\, symmetric unions too are ribbon. Like the slice-ribbon question\,\n
one may ask whether every ribbon knot is a symmetric union. This is the c
ase for a high number of prime ribbon knots with up to 12 crossings as wel
l as some infinite families such as 2-bridge ribbon knots. However\, for s
ome composite ribbon knots no such presentation\n has yet been found. Moti
vated by this\, I showed that these composite knots do not admit a symmetr
ic union presentation with a single twisting region. In my talk\, I will f
irst introduce the problem and outline a few results. Then I will give my
proof\, which\n is a short argument that relies on a Dehn filling descript
ion of double branched cover and a result of Gordon and Luecke on reducibl
e fillings.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bülent Tosun (University of Alabama)
DTSTART:20201117T190000Z
DTEND:20201117T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/11
DESCRIPTION:Title: Symplectic and complex geometric aspects of the 3-manifold embed
ding problem in 4-space.\nby Bülent Tosun (University of Alabama) as
part of Brandeis Topology Seminar\n\n\nAbstract\nThe problem of embedding
one manifold into another has a long\, rich history\, and proved to be tre
mendously important for development of geometric topology since the 1950s.
In this talk I will focus on the 3-manifold embedding problem in 4-space.
Given a closed\, orientable 3-manifold Y\, it is of great interest but of
ten a difficult problem to determine whether Y may be smoothly embedded in
R^4. This is the case even for integer homology spheres\, and restricting
to special classes such as Seifert manifolds\, the problem is open in gen
eral\, with positive answers for some such manifolds and negative answers
in other cases. On the other hand\, under additional geometric considerati
ons coming from symplectic geometry (such as hypersurfaces of contact type
) and complex geometry (such as the boundaries of holomorphically and/or r
ationally convex Stein domains)\, the problems become tractable and in cer
tain cases a uniform answer is possible. For example\, recent work shows f
or Brieskorn homology spheres: no such 3-manifold admits an embedding as a
hypersurface of contact type in R^4\, which is to say as the boundary of
a region that is convex from the point of view of symplectic geometry. In
this talk I will provide further context and motivations for this result\,
and give some details of the proof. \n\nThis is joint work with Tom Mark.
\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carolyn Abbott (Columbia University)
DTSTART:20201201T190000Z
DTEND:20201201T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/12
DESCRIPTION:Title: Free products and random walks in acylindrically hyperbolic grou
ps\nby Carolyn Abbott (Columbia University) as part of Brandeis Topolo
gy Seminar\n\n\nAbstract\nAbstract: The properties of a random walk on a g
roup which acts on a hyperbolic metric space have been well-studied in rec
ent years. In this talk\, I will focus on random walks on acylindrically
hyperbolic groups\, a class of groups which includes mapping class groups\
, Out(F_n)\, and right-angled Artin and Coxeter groups\, among many others
. I will discuss how a random element of such a group interacts with fixe
d subgroups\, especially so-called hyperbolically embedded subgroups. In
particular\, I will discuss when the subgroup generated by a random elemen
t and a fixed subgroup is a free product\, and I will also describe some o
f the geometric properties of that free product. This is joint work with M
ichael Hull.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yulan Qing (Fudan University)
DTSTART:20201208T190000Z
DTEND:20201208T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/13
DESCRIPTION:Title: The Large Scale Geometry of Big Mapping Class Groups\nby Yul
an Qing (Fudan University) as part of Brandeis Topology Seminar\n\n\nAbstr
act\nAbstract: In this talk\, we introduce the framework of the coarse geo
metry of non-locally compact groups in the setting of big mapping class gr
oups\, as studied by Rosendal. We will discuss the characterization result
s of Mann-Rafi and Horbez-Qing-Rafi that illustrate big mapping groups' ri
ch geometric and algebraic structures. We will outline the proofs in these
results and their implications. If time permits\, we will discuss some op
en problems in this area.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chris Leininger (Rice University)
DTSTART:20210202T190000Z
DTEND:20210202T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/14
DESCRIPTION:Title: Billiards\, symbolic coding\, and cone metrics\nby Chris Lei
ninger (Rice University) as part of Brandeis Topology Seminar\n\n\nAbstrac
t\nGiven a polygon in the Euclidean or hyperbolic plane a billiard traject
ory in the polygon is the geodesic path of a particle in the polygon bounc
ing off the sides so that the angle of reflection is equal to the angle in
cidence. A billiard trajectory determines a symbolic coding via the sides
of the polygon encountered. In this talk I will describe joint work with
Erlandsson and Sadanand showing the extent to which the set of all coding
sequences\, the bounce spectrum\, determines the shape of a hyperbolic po
lygon. We completely characterize those polygons which are billiard rigid
(the generic case)\, meaning that they are determined up to isometry by t
heir bounce spectrum. When rigidity fails for a polygon P\, we parameteri
ze the space of polygons having the same bounce spectrum at P. These resu
lts for billiards are a consequence of a rigidity/flexibility theorem for
negatively curved hyperbolic cone metrics. In the talk I will explain the
theorem about hyperbolic billiards\, comparing/contrasting it with the Eu
clidean case (earlier work with Duchin\, Erlandsson\, and Sadanand). Then
I will explain the relationship with hyperbolic cone metrics\, state our
rigidity/flexibility theorem for such metrics\, and as time allows describ
e some of the ideas involved in the proofs.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kasia Jankiewicz (University of Chicago)
DTSTART:20210406T180000Z
DTEND:20210406T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/15
DESCRIPTION:Title: Splittings of Artin groups\nby Kasia Jankiewicz (University
of Chicago) as part of Brandeis Topology Seminar\n\n\nAbstract\nWe show th
at many 2-dimensional Artin groups split as graphs of finite rank free gro
ups. In particular\, this is true for all triangle Artin groups A(m\,n\,p)
where m\,n\,p>2\, or m=2 and n\,p>3. For many of those groups\, we use th
e splitting to prove that the Artin group is residually finite. In particu
lar\, all triangle Artin groups with even labels are residually finite.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Golla (Université de Nantes)
DTSTART:20210209T190000Z
DTEND:20210209T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/16
DESCRIPTION:Title: 3-manifolds that bound no definite 4-manifold\nby Marco Goll
a (Université de Nantes) as part of Brandeis Topology Seminar\n\n\nAbstra
ct\nAll 3-manifolds bound 4-manifolds\, and many construction of 3-manifol
ds automatically come with a 4-manifold bounding it. Often times these 4-m
anifolds have definite intersection form. Using Heegaard Floer correction
terms and an analysis of short characteristic covectors in bimodular latti
ces\, we give an obstruction for a 3-manifold to bound a definite 4-manifo
ld\, and produce some concrete examples. This is joint work with Kyle Lars
on.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hans Boden (McMaster University)
DTSTART:20210216T190000Z
DTEND:20210216T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/17
DESCRIPTION:Title: The Gordon-Litherland pairing for knots in thickened surfaces\nby Hans Boden (McMaster University) as part of Brandeis Topology Semina
r\n\n\nAbstract\nWe introduce the Gordon-Litherland pairing for knots and
links in thickened surfaces that bound unoriented spanning surfaces. Using
the GL pairing\, we define signature and determinant invariants. We rela
te the invariants to those derived from the Tait graph and Goeritz matrice
s. These invariants depend only on the $S^*$ equivalence class of the span
ning surface\, and the determinants give a simple criterion to check if th
e knot or link is minimal genus. The GL pairing is isometric to the relati
ve intersection pairing on a 4-manifold obtained as the 2-fold cover along
the surface. These results are joint work with M. Chrisman and H. Karimi.
One can also use the GL pairing to give a topological characterization of
alternating links in thickened surfaces\, extending the results of J. Gre
ene and J. Howie.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kevin Schreve (University of Chicago)
DTSTART:20210223T190000Z
DTEND:20210223T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/18
DESCRIPTION:Title: Generalized Tits Conjecture for Artin groups\nby Kevin Schre
ve (University of Chicago) as part of Brandeis Topology Seminar\n\n\nAbstr
act\nIn 2001\, Crisp and Paris showed the squares of the standard generato
rs of an Artin group generate an "obvious" right-angled Artin subgroup. Th
is resolved an earlier conjecture of Tits. I will introduce a generalizati
on of this conjecture\, where we ask that a larger set of elements generat
es another "obvious" right-angled Artin subgroup.\nI will give evidence th
at this is a good generalization\, explain what classes of Artin groups we
can prove it for\, and give some applications. All of it is joint work wi
th Kasia Jankiewicz.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Maria Cumplido (Universidad de Sevilla)
DTSTART:20210316T180000Z
DTEND:20210316T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/19
DESCRIPTION:Title: Parabolic subgroups of large-type Artin groups\nby Maria Cum
plido (Universidad de Sevilla) as part of Brandeis Topology Seminar\n\n\nA
bstract\nArtin groups are a natural generalisation of braid groups from an
algebraic point of view: in the same way that braids are obtained from th
e presentation of the symmetric group\, other Coxeter groups give rise to
more general Artin groups. There are very few results proven for every Art
in group. To study them\, specialists have focused on some special kind of
subgroup\, called "parabolic subgroups". These groups are used to build
important simplicial complexes\, as the Deligne complex or the recent comp
lex of irreducible parabolic subgroups. The question "Is the intersection
of parabolic subgroups a parabolic subgroup?" is a very basic question who
se answer is only known for spherical Artin groups and RAAGs. In this talk
\, we will see how we can answer this question in Artin groups of large ty
pe\, by using the geometric realisation of the poset of parabolic subgroup
s\, that we have named "Artin complex". In particular\, we will show that
this complex in the large case has a property called sistolicity (a sort o
f weak CAT(0) property) that allows us to apply techniques from geometric
group theory. This is a joint work with Alexandre Martin and Nicolas Vasko
u.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Delphine Moussard (Université de Aix-Marseille)
DTSTART:20210323T180000Z
DTEND:20210323T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/20
DESCRIPTION:Title: A triple point invariant and the slice and ribbon genera\nby
Delphine Moussard (Université de Aix-Marseille) as part of Brandeis Topo
logy Seminar\n\n\nAbstract\nThe T-genus of a knot is the minimal number of
borromean-type triple points on a normal singular disk with no clasp boun
ded by the knot\; it is an upper bound for the slice genus. Kawauchi\, Shi
buya and Suzuki characterized the slice knots by the vanishing of their T-
genus. I will explain how this generalizes to provide a 3-dimensional char
acterization of the slice genus. Further\, I will show that the difference
between the T-genus and the slice genus can be arbitrarily large. Finally
\, I will introduce the ribbon counterpart of the T-genus\, which is an up
per bound for the ribbon genus\, and we will see that the T-genus and the
ribbon T-genus coincide for all knots if and only if all slice knots are r
ibbon.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Piotr Przytycki (McGill University)
DTSTART:20210413T180000Z
DTEND:20210413T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/21
DESCRIPTION:Title: Tail equivalence of unicorn paths\nby Piotr Przytycki (McGil
l University) as part of Brandeis Topology Seminar\n\n\nAbstract\nLet S be
an orientable surface of finite type. Using Pho-On's infinite unicorn pat
hs\, we prove the hyperfiniteness of the orbit equivalence relation coming
from the action of the mapping class group of S on the Gromov boundary of
the arc graph of S. This is joint work with Marcin Sabok.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:William Ballinger (Princeton University)
DTSTART:20210309T190000Z
DTEND:20210309T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/22
DESCRIPTION:Title: Concordance invariants from Khovanov homology\nby William Ba
llinger (Princeton University) as part of Brandeis Topology Seminar\n\n\nA
bstract\nThe Lee differential and Rasmussen's E(-1) differential acting on
\nKhovanov homology combine to give a pair of cancelling differentials\,\n
an algebraic structure that has been studied in the context of knot\nFloer
homology. I will describe some concordance invariants that come\nfrom thi
s structure\, with applications to nonorientable genus bounds\nand linear
independence in the concordance group.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ryan Budney (University of Victoria)
DTSTART:20210330T180000Z
DTEND:20210330T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/23
DESCRIPTION:Title: Isotopy in dimension 4\nby Ryan Budney (University of Victor
ia) as part of Brandeis Topology Seminar\n\n\nAbstract\nThis talk will des
cribe a diffeomorphism of "the barbell manifold" and what it tells us abou
t smooth isotopy of 3-manifolds in some small 4-manifolds. Specifically\,
the "barbell" is the (4\,2)-handlebody of genus 2\, i.e. the boundary conn
ect-sum of two copies of $S^2 \\times D^2$. We show that the mapping class
group of the barbell manifold\, i.e. $\\pi_0 Diff(Barbell)$\, where the d
iffeomorphisms fix the boundary pointwise\, is infinite cyclic -- after pe
rhaps modding out by the mapping class group of $D^4$. We then consider em
bedding the barbell into various 4-manifolds\, and the question of whether
or not the natural extension of the barbell diffeomorphism is isotopicall
y trivial in these 4-manifolds. From this we can conclude that the mapping
class groups of both $S^1 \\times D^3$ and $S^1 \\times S^3$ are not fini
tely generated. For $S^1 \\times D^3$ the idea of the proof is to show the
se diffeomorphisms act non-trivially on the isotopy classes of reducing 3-
balls\, i.e. show $f(\\{1\\}\\times D^3)$ is not isotopic to $\\{1\\}\\tim
es D^3$. To do this\, we imagine $D^3$ as a 2-parameter family of interval
s\, thus $f(\\{1\\}\\times D^3)$ can be viewed as producing an element of
the 2nd homotopy group of the space of smooth embeddings of an interval in
$S^1 \\times D^3$. The core of the proof involves developing an invariant
that can detect the low-dimensional homotopy groups of embedding spaces.
These invariants can be thought of as Vassiliev invariants.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:No seminar
DTSTART:20210420T180000Z
DTEND:20210420T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/24
DESCRIPTION:by No seminar as part of Brandeis Topology Seminar\n\nAbstract
: TBA\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hannah Schwartz (Princeton University)
DTSTART:20210427T180000Z
DTEND:20210427T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/25
DESCRIPTION:Title: The failure of the 4D light bulb theorem with dual spheres of no
n-zero square\nby Hannah Schwartz (Princeton University) as part of Br
andeis Topology Seminar\n\n\nAbstract\nExamples of surfaces embedded in a
4-manifold that are homotopic but not isotopic are neither rare nor surpri
sing. It is then quite amazing that\, in settings such as the recent 4D li
ght bulb theorems of both Gabai and Schneiderman-Teichner\, the existence
of an embedded sphere of square zero intersecting a surface transversally
in a single point has the power to "upgrade" a homotopy of that surface in
to a smooth isotopy. We will discuss the limitations of this phenonemon\,
using contractible 4-manifolds called corks to produce homotopic spheres i
n a 4-manifold with a common dual of non-zero square that are not smoothly
isotopic.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dan Margalit (Georgia Tech)
DTSTART:20210504T180000Z
DTEND:20210504T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/26
DESCRIPTION:Title: Homomorphisms of braid groups and totally symmetric sets\nby
Dan Margalit (Georgia Tech) as part of Brandeis Topology Seminar\n\n\nAbs
tract\nIn joint work with Kevin Kordek and Lei Chen\, we completely classi
fy homomorphisms from the braid group on n strands to the braid group on 2
n strands. One of the main new tools is the theory of totally symmetric s
ets\, which has found many other applications. We will begin with a surve
y of known classifications of homomorphisms of braid groups\, and then exp
lain how to classify endomorphisms of the braid group using totally symmet
ric sets.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michael Sullivan (UMass Amherst)
DTSTART:20211005T180000Z
DTEND:20211005T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/27
DESCRIPTION:Title: Displacing Legendrian submanifolds in contact geometry\nby M
ichael Sullivan (UMass Amherst) as part of Brandeis Topology Seminar\n\n\n
Abstract\nLagrangian and Legendrian submanifolds of symplectic and contact
manifolds are sometimes ``flexible" like smooth topology\, and sometimes
``rigid" like differential geometry. Pseudo-holomorphic curves\, algebraic
ally packaged into various Floer-theory or Gromov-Witten-theory invariants
\, have played a (maybe even ``the") main role in proving rigidity result
s. But if the invariants vanish\, does this mean the objects of study are
flexible? I will discuss\, using the barcodes of a persistence Floer-type
homology\, how to extract (sometimes optimal) quantitative rigidity result
s for Legendrian submanifolds\, even when the traditional Floer-theory inv
ariants vanish. I plan to give the talk remotely\, but in real-time\, to
keep the pace more accessible. This is joint work with Georgios Dimitroglo
u Rizell.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yajit Jain (Brown University)
DTSTART:20211012T180000Z
DTEND:20211012T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/28
DESCRIPTION:Title: Topologically Trivial Families of Smooth h-Cobordisms\nby Ya
jit Jain (Brown University) as part of Brandeis Topology Seminar\n\n\nAbst
ract\nIn this talk we will discuss topologically trivial families of smoot
h h-cobordisms. Using work of Dwyer\, Weiss\, and Williams\, we can assign
a K-theoretic invariant to these bundles\, the smooth structure character
istic\, which is closely related to the higher Franz–Reidemeister torsio
n invariants studied by Igusa. After describing constructions of these bun
dles due to Goette and Igusa\, we will indicate how one can compute the sm
ooth structure characteristic using Morse theory\, and outline a proof of
their Rigidity Conjecture. Time permitting\, we will also briefly discuss
a relationship between these invariants and symplectic topology.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniel Alvarez-Gavela (MIT)
DTSTART:20211019T180000Z
DTEND:20211019T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/29
DESCRIPTION:Title: The nearby Lagrangian conjecture from the K-theoretic viewpoint.
\nby Daniel Alvarez-Gavela (MIT) as part of Brandeis Topology Seminar\
n\n\nAbstract\nI will discuss two K-theoretic aspects of the nearby Lagran
gian conjecture. The first is joint work with M. Abouzaid\, S. Courte and
T. Kragh and uses a factoring of the Waldhausen derivative to obtain new r
estrictions on the smooth structure of nearby Lagrangians. The second is j
oint work in progress with K. Igusa and M. Sullivan and attempts to use a
higher Whitehead torsion invariant to obtain new restrictions on the stabl
e isomorphism classes of tube bundles which may be used to generate nearby
Lagrangians.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Zihao Liu (Brandeis University)
DTSTART:20211026T180000Z
DTEND:20211026T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/30
DESCRIPTION:Title: Scaled homology and topological entropy (in person)\nby Ziha
o Liu (Brandeis University) as part of Brandeis Topology Seminar\n\n\nAbst
ract\nIn this talk\, I will introduce a scaled homology theory\, lc-homolo
gy\, for metric spaces such that every metric space can be visually regard
ed as “locally contractible” with this newly-built homology. In additi
on\, after giving a brief introduction of topological entropy\, I will dis
cuss how to generalize one of the existing results of entropy conjecture\,
relaxing the smooth manifold restrictions on the compact metric spaces\,
by using lc-homology groups. This is joint work with Bingzhe Hou and Kiyos
hi Igusa.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jacob Russell (Rice University)
DTSTART:20211102T180000Z
DTEND:20211102T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/31
DESCRIPTION:Title: Searching for geometric finiteness using surface group extension
s\nby Jacob Russell (Rice University) as part of Brandeis Topology Sem
inar\n\n\nAbstract\nFarb and Mosher defined convex cocompact subgroups of
the mapping class group in analogy with convex cocompact Kleinian groups.
These subgroups have since seen immense study\, producing surprising appli
cations to the geometry of surface group extension and surface bundles. In
particular\, Hamenstadt plus Farb and Mosher proved that a subgroup of th
e mapping class groups is convex cocompact if and only if the correspondin
g surface group extension is Gromov hyperbolic.\n\nAmong Kleinian groups\,
convex cocompact groups are a special case of the geometrically finite gr
oups. Despite the progress on convex cocompactness\, no robust notion of g
eometric finiteness in the mapping class group has emerged. Durham\, Dowda
ll\, Leininger\, and Sisto recently proposed that geometric finiteness in
MCG(S) might be characterized by the corresponding surface group extension
being hierarchically hyperbolic instead of Gromov hyperbolic. We provide
evidence in favor of this hypothesis by proving that the surface group ext
ension of the stabilizer of a multicurve is hierarchically hyperbolic.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anthony Conway (MIT)
DTSTART:20211109T190000Z
DTEND:20211109T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/32
DESCRIPTION:Title: Stable diffeomorphism and homotopy equivalence (in person)\n
by Anthony Conway (MIT) as part of Brandeis Topology Seminar\n\n\nAbstract
\nIn this talk\, we consider the difference between stable diffeomorphism
and homotopy equivalence. Here\, two 2n-manifolds are called stably diffeo
morphic if they become diffeomorphic after connect summing with enough cop
ies of $S^n\\times S^n$. After providing some motivation from surgery the
ory\, we describe families of stably diffeomorphic manifolds that are not
pairwise homotopy equivalent. This is based on joint work with Crowley\, P
owell and Sixt.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lorenzo Ruffoni (Tufts University)
DTSTART:20211116T190000Z
DTEND:20211116T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/33
DESCRIPTION:Title: In person\nby Lorenzo Ruffoni (Tufts University) as part of
Brandeis Topology Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ivan Levcovitz (Tufts University)
DTSTART:20211123T190000Z
DTEND:20211123T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/34
DESCRIPTION:Title: Coxeter groups with connected Morse boundary\nby Ivan Levcov
itz (Tufts University) as part of Brandeis Topology Seminar\n\n\nAbstract\
nThe Morse boundary is a quasi-isometry invariant that encodes the possibl
e "hyperbolic" directions of a group. The topology of the Morse boundary c
an be challenging to understand\, even for simple examples. In this talk\,
I will focus on a basic topological property: connectivity and on a well-
studied class of CAT(0) groups: Coxeter groups. I will discuss a criteria
that guarantees that the Morse boundary of a Coxeter group is connected. I
n particular\, when we restrict to the right-angled case\, we get a full c
haracterization of right-angled Coxeter groups with connected Morse bounda
ry. This is joint work with Matthew Cordes.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cary Malkiewich (Binghamton University)
DTSTART:20211207T190000Z
DTEND:20211207T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/35
DESCRIPTION:Title: Fixed point theory and the higher characteristic polynomial\
nby Cary Malkiewich (Binghamton University) as part of Brandeis Topology S
eminar\n\n\nAbstract\nI'll give a highly revisionist account of classical
Nielsen fixed-point theory\, putting it in the context of modern trace met
hods by arguing that its central invariant is most naturally a class in to
pological Hochschild homology (THH). I'll then describe how this generaliz
es to periodic points and topological restriction homology (TR)\, and how
these invariants fit together to give a far-reaching generalization of the
characteristic polynomial from linear algebra. Much of this is joint work
with Ponto\, and separately with Campbell\, Lind\, Ponto\, and Zakharevic
h.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michah Sageev (Technion Institute)
DTSTART:20211130T190000Z
DTEND:20211130T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/36
DESCRIPTION:Title: Right angled Coxeter groups acting on CAT(0) cube complexes\
nby Michah Sageev (Technion Institute) as part of Brandeis Topology Semina
r\n\n\nAbstract\nWe will discuss a type of rigidity that one can hope for
in the setting of proper\, cocompact actions of right angled Coxeter group
s acting on CAT(0) cube complexes\, and some partial results in this direc
tion. This is joint work with Ivan Levcovitz.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marissa Miller (UIUC)
DTSTART:20220215T190000Z
DTEND:20220215T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/37
DESCRIPTION:Title: Hierarchical hyperbolicity and stability in handlebody groups\nby Marissa Miller (UIUC) as part of Brandeis Topology Seminar\n\n\nAbst
ract\nIn this talk\, we explore the geometry of the handlebody group\, i.e
. the mapping class group of a handlebody. These groups can be viewed as s
ubgroups of surface mapping class groups and on the surface seem similar\,
but based on the current state of research\, the geometry of handlebody g
roups appears to be very different than the geometry of surface mapping cl
ass groups. In this talk we will explore two different geometric notions:
hierarchical hyperbolicity (of which surface mapping class groups are the
prototype)\, and stable subgroups\, which have a nice characterization in
the surface mapping class groups in terms of the orbit map to the curve gr
aph. I will discuss how the genus two handlebody group is also hierarchica
lly hyperbolic and has an analogous stable subgroup characterization\, and
I will also discuss what goes wrong in the higher genus cases that preven
ts hierarchical hyperbolicity and the existence of an analogous stable sub
group characterization.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jingyin Huang (Ohio State University)
DTSTART:20220310T203000Z
DTEND:20220310T213000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/39
DESCRIPTION:Title: The Helly geometry of some Garside and Artin groups\nby Jing
yin Huang (Ohio State University) as part of Brandeis Topology Seminar\n\n
\nAbstract\nGarside groups and Artin groups are two generalizations of bra
id groups. We show that weak Garside groups of finite type and FC-type Art
in groups acts geometrically metric spaces which are non-positively in an
appropriate sense\, i.e. they act geometrically on Helly graphs\, as well
as metric spaces with convex geodesic bicombings. We will also discuss sev
eral algorithmic and \, geometric and topological consequences of the exis
tence of such an action. This is joint work with D. Osajda.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bernard Badzioch (University of Buffalo)
DTSTART:20220301T190000Z
DTEND:20220301T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/40
DESCRIPTION:Title: Categorical algebra and mapping spaces\nby Bernard Badzioch
(University of Buffalo) as part of Brandeis Topology Seminar\n\n\nAbstract
\nMany classical results in homotopy theory show that iterated loop spaces
\, i.e. pointed mapping spaces \nfrom a sphere\, can be identified with sp
aces equipped with a certain algebraic structure described by means of an
operad\, a prop\, an algebraic theory etc. A natural questions is whether
analogous algebraic description can be used to characterize mapping spaces
with the domain given by a space different than a sphere.\n \nThe talk wi
ll describe some results in this area.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/40/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lev Tostopyat-Nelip (Michigan State University)
DTSTART:20220315T180000Z
DTEND:20220315T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/41
DESCRIPTION:Title: Floer homology and quasipositive surfaces\nby Lev Tostopyat-
Nelip (Michigan State University) as part of Brandeis Topology Seminar\n\n
\nAbstract\nOzsvath and Szabo have shown that knot Floer homology detects
the genus of a knot - the largest Alexander grading of a non-trivial homol
ogy class is equal to the genus.\nWe give a new contact geometric interpre
tation of this fact by realizing such a class via the transverse knot inva
riant introduced by Lisca\, Ozsvath\, Stipsicz and Szabo. Our approach rel
ies on the "convex decomposition theory" of Honda\, Kazez and Matic - a co
ntact geometric interpretation of Gabai's sutured hierarchies. \nWe use th
is new interpretation to study the "next-to-top" summand of knot Floer hom
ology\, and to show that Heegaard Floer homology detects quasi-positive Se
ifert surfaces. Some of this talk represents joint work with Matthew Hedde
n.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dave Auckly (Kansas State University)
DTSTART:20220322T180000Z
DTEND:20220322T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/42
DESCRIPTION:Title: Branched covers in low dimensions.\nby Dave Auckly (Kansas S
tate University) as part of Brandeis Topology Seminar\n\n\nAbstract\nThis
talk will begin with several basic examples of branched covers.\nIt will t
hen present several results about the existence and non-existence of branc
hed covers in low dimensional settings.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lei Chen (University of Maryland)
DTSTART:20220329T180000Z
DTEND:20220329T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/43
DESCRIPTION:Title: Actions of Homeo and Diffeo groups on manifolds\nby Lei Chen
(University of Maryland) as part of Brandeis Topology Seminar\n\n\nAbstra
ct\nIn this talk\, I discuss the general question of how to obstruct and c
onstruct group actions on manifolds. I will focus on large groups like Hom
eo(M) and Diff(M) about how they can act on another manifold N. The main r
esult is an orbit classification theorem\, which fully classifies possible
orbits. I will also talk about some low dimensional applications and open
questions. This is a joint work with Kathryn Mann.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Maria Cumplido (University of Seville)
DTSTART:20220405T180000Z
DTEND:20220405T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/44
DESCRIPTION:Title: Conjugacy stability in Artin groups\nby Maria Cumplido (Univ
ersity of Seville) as part of Brandeis Topology Seminar\n\n\nAbstract\nArt
in (or Artin-Tits) groups are generalizations of braid groups that are def
ined using a finite set of generators $S$ and relations $abab\\cdots=baba\
\cdots$\, where both words of the equality have the same length. Although
this definition is quite simple\, there are very few results known for Art
in groups in general. Classic problems as the word problem or the conjugac
y problem are still open. In this talk\, we study a problem concerning a f
amily of subgroups of Artin groups: parabolic subgroups. These subgroups h
ave proven to be useful when studying Artin groups (for example\, they are
used to build interesting simplicial complexes)\, but again\, we do not k
now much about them in general. \n\nOur problem will be the following: Giv
en two conjugate elements of a parabolic subgroup $P$ of an Artin group $A
$\, are they conjugate via an element of $P$? This is called the conjugacy
stability problem. In 2014\, González-Meneses proved that this is always
true for braids\, that is\, geometric embeddings of braids do not merge c
onjugacy classes. In an article with Calvez and Cisneros de la Cruz\, we g
ave a classification for spherical Artin groups and proved that the answer
to the question is not always affirmative. In this talk\, we will explain
how to give an algorithm to solve this problem for every Artin group sati
sfying three properties that are conjectured to be always true.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/44/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aleksandra Kjuchukova (Notre Dame University)
DTSTART:20220412T180000Z
DTEND:20220412T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/45
DESCRIPTION:Title: H-slice knots in $\\#^m\\mathbb{CP}^2$\nby Aleksandra Kjuchu
kova (Notre Dame University) as part of Brandeis Topology Seminar\n\n\nAbs
tract\nLet $K\\subset S^3$ be a knot and let $X$ be a closed smooth four-m
anifold. Does $K$ bound a smooth/locally flat null-homologous disk properl
y embedded in $X$ minus an open ball? (If so\, we say $K$ is smoothly/top
ologically H-slice in $X$.) The classification of H-slice knots in a 4-man
ifold $X$ can help detect exotic smooth structures on $X$. I will describe
new tools to compute the (smooth or topological) $\\mathbb{CP}^2$ slicing
number of a knot $K$\, which is the smallest $m$ such that $K$ is (smooth
ly or topologically) H-slice in $\\#^m\\mathbb{CP}^2$. This talk is based
on arXiv:2112.14596.\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:No talk
DTSTART:20220308T190000Z
DTEND:20220308T203000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/46
DESCRIPTION:by No talk as part of Brandeis Topology Seminar\n\nAbstract: T
BA\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/46/
END:VEVENT
BEGIN:VEVENT
SUMMARY:No talk
DTSTART:20220419T180000Z
DTEND:20220419T193000Z
DTSTAMP:20260422T230717Z
UID:BrandeisTopology/47
DESCRIPTION:by No talk as part of Brandeis Topology Seminar\n\nAbstract: T
BA\n
LOCATION:https://researchseminars.org/talk/BrandeisTopology/47/
END:VEVENT
END:VCALENDAR