BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Jim Belk (University of St Andrews) DTSTART:20200616T190000Z DTEND:20200616T200000Z DTSTAMP:20260422T212607Z UID:OSUGGT/1 DESCRIPTION:Title: O n Finitely Presented Groups that Contain Q\nby Jim Belk (University of St Andrews) as part of Ohio State Topology and Geometric Group Theory Sem inar\n\n\nAbstract\nIt is a consequence of Higman's embedding theorem that the additive group Q of rational numbers can be embedded into a finitely presented group. Though Higman's proof is constructive\, the resulting gro up presentation would be very large and ungainly. In 1999\, Martin Bridson and Pierre de la Harpe asked for an explicit and "natural" example of a f initely presented group that contains an embedded copy of Q. In this talk\ , we describe some solutions to this problem related to Thompson's groups F\, T\, and V\, including a new simple group of type F infinity that conta ins Q. This is joint work with James Hyde and Francesco Matucci.\n LOCATION:https://researchseminars.org/talk/OSUGGT/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Johnny Nicholson (University College London) DTSTART:20200714T180000Z DTEND:20200714T190000Z DTSTAMP:20260422T212607Z UID:OSUGGT/2 DESCRIPTION:Title: P rojective modules and the homotopy classification of CW-complexes\nby Johnny Nicholson (University College London) as part of Ohio State Topolog y and Geometric Group Theory Seminar\n\n\nAbstract\nA basic question in th e homotopy classification of CW-complexes is to ask for which finitely pre sented groups $G$ does $X \\vee S^2 \\simeq Y \\vee S^2$ imply $X \\simeq Y$\, where $X$ and $Y$ are finite 2-complexes with fundamental group $G$. Despite early interest by Cockroft-Swan and Dyer-Sieradski\, it wasn’t u ntil 1976 that examples of non-cancellation were found by Dunwoody and Met zler. This led Browning to complete the classification in the finite abeli an case. In recent years\, applications to Wall’s D2 problem and the cla ssification of manifolds have sparked renewed interest in this problem. In this talk\, we will show how the case where $G$ has periodic cohomology c an largely be reduced to a question about projective $\\mathbb{Z} G$ modul es. We then resolve this by generalising results of Swan from the 1980s.\n LOCATION:https://researchseminars.org/talk/OSUGGT/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Mauricio Bustamante (University of Cambridge) DTSTART:20201027T150000Z DTEND:20201027T160000Z DTSTAMP:20260422T212607Z UID:OSUGGT/3 DESCRIPTION:Title: D iffeomorphisms of solid tori\nby Mauricio Bustamante (University of Ca mbridge) as part of Ohio State Topology and Geometric Group Theory Seminar \n\n\nAbstract\nThe homotopy groups of the diffeomorphism group of a high dimensional manifold with infinite fundamental group can be infinitely gen erated. The simplest example of this sort is the solid torus T=S^1\\times D^{d-1}. In fact\, using surgery and pseudoisotopy theory\, it is possible to show that in the range of degrees up to (roughly) d/3\, the homotopy g roups of Diff(T) contain infinitely generated torsion subgroups.\n\nIn thi s talk\, I will discuss an alternative point of view to study Diff(T) whic h does not invoke pseudoisotopy theory: when d=2n\, we interpret Diff(T) a s the "difference" between diffeomorphisms and certain self-embeddings of the manifold X_g obtained as the connected sum of T with the g-fold connec ted sum of S^n \\times S^n.\n\nWe will see how infinitely generated torsio n subgroups appear from this perspective\, and that they can be found even up to degrees d/2. This is ongoing joint work with O. Randal-Williams.\n LOCATION:https://researchseminars.org/talk/OSUGGT/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Waltraud Lederle (Université Catholique de Louvain) DTSTART:20200827T150000Z DTEND:20200827T160000Z DTSTAMP:20260422T212607Z UID:OSUGGT/4 DESCRIPTION:Title: C onjugacy in Neretin's group\nby Waltraud Lederle (Université Catholiq ue de Louvain) as part of Ohio State Topology and Geometric Group Theory S eminar\n\n\nAbstract\nWe explain when two almost automorphisms of a regula r tree are conjugate. Our main focus will be on non-elliptic elements\, wh ere we can use strand diagrams introduced by Belk and Matucci to describe conjugacy in Thompson's V. This is joint work with Gil Goffer.\n LOCATION:https://researchseminars.org/talk/OSUGGT/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Sam Shepherd (University of Oxford) DTSTART:20200825T150000Z DTEND:20200825T160000Z DTSTAMP:20260422T212607Z UID:OSUGGT/5 DESCRIPTION:Title: Q uasi-isometric rigidity of generic cyclic HNN extensions of free groups\nby Sam Shepherd (University of Oxford) as part of Ohio State Topology a nd Geometric Group Theory Seminar\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/OSUGGT/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Mark Pengitore (OSU) DTSTART:20200610T150000Z DTEND:20200610T160000Z DTSTAMP:20260422T212607Z UID:OSUGGT/7 DESCRIPTION:Title: C oarse embeddings and homological filling functions\nby Mark Pengitore (OSU) as part of Ohio State Topology and Geometric Group Theory Seminar\n\ nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/OSUGGT/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Benjamin Steinberg (CCNY) DTSTART:20200929T150000Z DTEND:20200929T160000Z DTSTAMP:20260422T212607Z UID:OSUGGT/8 DESCRIPTION:Title: S implicity of Nekrashevych algebras of contracting self-similar groups\ nby Benjamin Steinberg (CCNY) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nA self-similar group is a group $G$ a cting on the Cayley graph of a finitely generated free monoid $X^*$ (i.e.\ , regular rooted tree) by automorphisms in such a way that the self-simila riy of the tree is reflected in the group. The most common examples are ge nerated by the states of a finite automaton. Many famous groups like Grigo rchuk's 2-group of intermediate growth are of this form.\n\nNekrashevych a ssociated $C^*$-algebras and algebras with coefficients in a field to self -similar groups. In the case $G$ is trivial\, the algebra is the classical Leavitt algebra\, a famous finitely presented simple algebra. \n\nNekrash evych showed the algebra associated to the Grigorchuk group is not simple in characteristic 2\, but Clark\, Exel\, Pardo\, Sims and Starling showed its Nekrashevych algebra is simple over all other fields. Nekrashevych the n showed that the algebra associated to the Grigorchuk-Erschler group is n ot simple over any field (the first such example). \n\nThe Grigorchuk and Grigorchuk-Erschler groups are contracting self-similar groups. This impor tant class of self-similar groups includes Gupta-Sidki p-groups and many i terated monodromy groups like the Basilica group. Nekrashevych proved alge bras associated to contacting groups are finitely presented. \n\nIn this t alk we discuss a recent result of the speaker and N. Szakacs (York/Szeged) characterizing simplicity of Nekrashevych algebras of contracting groups. In particular\, we give an algorithm for deciding simplicity given an aut omaton generating the group. We apply our results to several families of c ontracting groups like Gupta-Sidki groups and Sunic's generalizations of G rigorchuk's group associated to polynomials over finite fields.\n LOCATION:https://researchseminars.org/talk/OSUGGT/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Lvzhou Chen (University of Texas-Austin) DTSTART:20200922T150000Z DTEND:20200922T160000Z DTSTAMP:20260422T212607Z UID:OSUGGT/9 DESCRIPTION:Title: S table commutator lengths of integral chains in right-angled Artin groups\nby Lvzhou Chen (University of Texas-Austin) as part of Ohio State Topo logy and Geometric Group Theory Seminar\n\n\nAbstract\nIt follows from the orems of Agol and Kahn-Markovic that the fundamental group of any closed h yperbolic 3-manifold contains a special subgroup of finite index. Very lit tle is known about how large the index needs to be. Motivated by this\, in this joint work with Nicolaus Heuer\, we study stable commutator lengths (scl) of integral chains in right-angled Artin groups (RAAGs). Topological ly\, an integral 1-chain in a group G is a collection of loops in the K(G\ ,1) space with integral weights\, and its scl is the least complexity of s urfaces bounding the weighted loops. We show that the infimal positive scl of integral chains in any RAAG is positive\, and its size explicitly depe nds on the defining graph of the RAAG up to a multiplicative constant 12. In particular\, the size is non-uniform among RAAGs\, which is unexpected. \n LOCATION:https://researchseminars.org/talk/OSUGGT/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Laurent Bartholdi (Goettingen) DTSTART:20201015T150000Z DTEND:20201015T160000Z DTSTAMP:20260422T212607Z UID:OSUGGT/10 DESCRIPTION:Title: Domino problems on graphs and groups\nby Laurent Bartholdi (Goettingen ) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nA bstract\nFor a fixed edge-labelled graph\, the "domino problem" asks: "giv en a collection of labelled dominoes (with numbers on their ends)\, can on e put a domino on each edge of the graph in such a manner that edge labels and vertex numbers match?''\n\nIn spite of its naive appearence\, this pr oblem is deeply connected to (monadic\, second-order) logic\; remarkably\, it is undecidable for graphs such as the infinite square grid – the "Wa ng tiling problem".\n\nI will consider it on graphs produced from a group action: Cayley graphs\, Schreier graphs. I will exhibit a class of graphs for which the problem is decidable\, as well as interesting examples not c ontaining grids yet also having undecidable domino problem.\n\nPart of thi s is joint work with Ville Salo.\n LOCATION:https://researchseminars.org/talk/OSUGGT/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Ilir Snopce (Rio de Janeiro) DTSTART:20201203T160000Z DTEND:20201203T170000Z DTSTAMP:20260422T212607Z UID:OSUGGT/13 DESCRIPTION:Title: Retracts in free groups\nby Ilir Snopce (Rio de Janeiro) as part of Oh io State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nA subg roup R of a group G is said to be a retract of G if there is a homomorphis m r : G → R that restricts to the identity on R. I will talk about retra cts in free groups. In particular\, I will discuss the following question raised by Bergman: Let F be a free group of finite rank and let R be a ret ract of F. Is it H ∩ R is a retract of H for every finitely generated s ubgroup H of F? \n\nThis talk is based on a joint work with Slobodan Tanus hevski and Pavel Zalesskii.\n LOCATION:https://researchseminars.org/talk/OSUGGT/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Marcin Sabok (McGill University) DTSTART:20191105T160000Z DTEND:20191105T170000Z DTSTAMP:20260422T212607Z UID:OSUGGT/15 DESCRIPTION:Title: Hyperfiniteness at Gromov boundaries\nby Marcin Sabok (McGill Universi ty) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\ nAbstract\nI will discuss recent results establishing hyperfiniteness of e quivalence relations induced by actions on Gromov boundaries of various hy perbolic spaces. This includes boundary actions of hyperbolic groups (join t work with T. Marquis) and actions of the mapping class group on boundari es of the arc graph and the curve graph (joint work with P. Przytycki)\n LOCATION:https://researchseminars.org/talk/OSUGGT/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Alex Margolis (Vanderbilt University) DTSTART:20201110T160000Z DTEND:20201110T170000Z DTSTAMP:20260422T212607Z UID:OSUGGT/16 DESCRIPTION:Title: Topological completions of quasi-actions and discretisable spaces\nby Alex Margolis (Vanderbilt University) as part of Ohio State Topology and G eometric Group Theory Seminar\n\n\nAbstract\nA fundamental problem in geom etric group theory is the\nstudy of quasi-actions. We introduce and inves tigate discretisable\nspaces: spaces for which every cobounded quasi-actio n can be\nquasi-conjugated to an isometric action on a locally finite grap h. Work\nof Mosher-Sageev-Whyte shows that non-abelian free groups are\ndi scretisable\, but the property holds much more generally. For instance\,\n every non-elementary hyperbolic group that is not virtually isomorphic\nto a cocompact lattice in rank one Lie group is discretisable.\n\nAlong the way\, we study the coarse geometry of groups containing almost\nnormal/com mensurated subgroups\, and we introduce the concept of the\ntopological co mpletion of a quasi-action. The topological completion is\na locally compa ct group\, well-defined up to a compact normal subgroup\,\nreflecting the geometry of the quasi-action. We give several\napplications of the tools w e develop. For instance we show that any\nfinitely generated group quasi-i sometric to a ‬Z‭-by-hyperbolic group is\nalso Z-by-hyperbolic\, and p rove quasi-isometric rigidity for a large\nclass of right-angled Artin gro ups.\n LOCATION:https://researchseminars.org/talk/OSUGGT/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Xiaolei Wu (Bielefeld University) DTSTART:20201117T160000Z DTEND:20201117T170000Z DTSTAMP:20260422T212607Z UID:OSUGGT/17 DESCRIPTION:Title: On the poly-freeness of Artin groups\nby Xiaolei Wu (Bielefeld Univers ity) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n \nAbstract\nArtin group is an important class of groups under intensive st udy in recent years. It is a generalization of the braid groups. Bestvina asks whether all Artin groups are virtually poly-free. In this talk\, we f irst give an introduction to poly-free groups and Artin groups. We explain some connections with the Farrell-Jones Conjecture. Then we explain some recent progress of Bestvina's question. In particular\, we will give a sho rt proof of the fact that Even Artin groups of FC-type are polyfree. Part of this is joint work with Benjamin Brück and Dawid Kielak.\n LOCATION:https://researchseminars.org/talk/OSUGGT/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Woodhouse (University of Oxford) DTSTART:20201119T160000Z DTEND:20201119T170000Z DTSTAMP:20260422T212607Z UID:OSUGGT/18 DESCRIPTION:Title: Action rigidity of free products of hyperbolic manifold groups\nby Dan iel Woodhouse (University of Oxford) as part of Ohio State Topology and Ge ometric Group Theory Seminar\n\n\nAbstract\nGromov's program for understan ding finitely generated groups up to their large scale geometry considers three possible relations: quasi-isometry\, abstract commensurability\, and acting geometrically on the same proper geodesic metric space. A *common model geometry* for groups G and G' is a proper geodesic metric space on w hich G and G' act geometrically. A group G is *action rigid* if any group G' that has a common model geometry with G is abstractly commensurable to G. We show that free products of closed hyperbolic surface or 3-manifold g roups are action rigid. As a corollary\, we obtain torsion-free\, Gromov h yperbolic groups that are quasi-isometric\, but do not even virtually act on the same proper geodesic metric space.\n LOCATION:https://researchseminars.org/talk/OSUGGT/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Christoforos Neofytidis (Ohio State University) DTSTART:20210112T180000Z DTEND:20210112T190000Z DTSTAMP:20260422T212607Z UID:OSUGGT/19 DESCRIPTION:Title: Endomorphisms of mapping tori\nby Christoforos Neofytidis (Ohio State University) as part of Ohio State Topology and Geometric Group Theory Semi nar\n\n\nAbstract\nOne of the most fundamental results in 3-dimensional to pology\, proved in works of Gromov\, Mostow\, Wang and Waldhausen\, is tha t any self-map of non-zero degree of a mapping torus of a closed hyperboli c surface is homotopic to a homeomorphism if and only if the monodromy is not periodic. Key properties for the proof were the existence of hyperboli c structures or of non-vanishing semi-norms (such as the simplicial volume ). Using Algebra\, we give a new\, unified proof and generalise the above result in every dimension\, by replacing the hyperbolic surface with a cor responding higher dimensional aspherical manifold. More generally\, we wil l classify in terms of Hopf-type properties mapping tori of residually fin ite Poincaré Duality groups with non-zero Euler characteristic. It turns out that the rigidity behavior of these mapping tori with trivial center i s similar to that of non-elementary torsion-free hyperbolic groups.\n LOCATION:https://researchseminars.org/talk/OSUGGT/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Mike Davis (Ohio State University) DTSTART:20210119T180000Z DTEND:20210119T190000Z DTSTAMP:20260422T212607Z UID:OSUGGT/20 DESCRIPTION:Title: Bordifications of hyperplane arrangement complements and curve complexes o f spherical Artin groups\nby Mike Davis (Ohio State University) as par t of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\ nThe complement of an arrangement of hyperplanes in a complex vector space has a natural bordification to a manifold with corners formed by removing tubular neighborhoods of the hyperplanes and certain of their intersectio ns. When the arrangement is the complexification of a real simplicial arr angement\, the bordification closely resembles Harvey's bordification of t he braid group. The faces of the universal cover of the bordification ar e parameterized by the simplices of a simplicial complex\, the vertices of which are the irreducible ``parabolic subgroups'' of the fundamental grou p of the arrangement complement. When the arrangement is associated to a f inite reflection group\, we get the "curve complex" of the associated pure Artin group. In analogy with curve complexes for mapping class groups and with spherical buildings\, our curve complex has the homotopy type of a w edge of spheres. This is joint work with Jingyin Huang.\n LOCATION:https://researchseminars.org/talk/OSUGGT/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Berlyne (City University of New York) DTSTART:20210121T180000Z DTEND:20210121T190000Z DTSTAMP:20260422T212607Z UID:OSUGGT/21 DESCRIPTION:Title: Graph products as hierarchically hyperbolic groups\nby Daniel Berlyne (City University of New York) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nGiven a finite simplicial graph with a finitely generated group associated to each vertex\, the graph product i s defined by taking the free product of the vertex groups and adding commu tation relations between elements belonging to vertex groups that are conn ected by a edge in the graph. Common examples of graph products include ri ght-angled Artin groups (where all vertex groups are Z) and right-angled C oxeter groups (where all vertex groups are Z/2Z). Behrstock\, Hagen\, and Sisto showed that right-angled Artin groups exhibit a notion of non-positi ve curvature called hierarchical hyperbolicity\, with deep geometric conse quences such as a Masur-Minsky style distance formula\, finite asymptotic dimension\, and acylindrical hyperbolicity. By developing analogues of the cubical techniques employed by Behrstock-Hagen-Sisto\, we are able to gen eralise their result\, showing that any graph product with hierarchically hyperbolic vertex groups is itself a hierarchically hyperbolic group. In d oing so\, we answer two questions of Behrstock-Hagen-Sisto and two questio ns of Genevois. This is joint work with Jacob Russell.\n LOCATION:https://researchseminars.org/talk/OSUGGT/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Francis Wagner (Vanderbilt) DTSTART:20210126T180000Z DTEND:20210126T190000Z DTSTAMP:20260422T212607Z UID:OSUGGT/22 DESCRIPTION:Title: Torsion Subgroups of Groups with Quadratic Dehn Function\nby Francis W agner (Vanderbilt) as part of Ohio State Topology and Geometric Group Theo ry Seminar\n\n\nAbstract\nThe Dehn function of a finitely presented group\ , first introduced by Gromov\, is a useful invariant that is closely relat ed to the solvability of the group’s word problem. It is well-known that a finitely presented group is word hyperbolic if and only if it has sub-q uadratic (and thus linear) Dehn function. A result of Ghys and de la Harpe states that no word hyperbolic group can have a (finitely generated) infi nite torsion subgroup. We show that this property does not carry over to a ny class of groups of larger Dehn function. In particular\, for every m>1 and n sufficiently large (and either odd or divisible by 2^9)\, there exis ts a quasi-isometric embedding of the infinite free Burnside group B(m\,n) into a finitely presented group with quadratic Dehn function.\n LOCATION:https://researchseminars.org/talk/OSUGGT/22/ END:VEVENT BEGIN:VEVENT SUMMARY:Panagiots Konstantis (Marburg) (Marburg) DTSTART:20210128T180000Z DTEND:20210128T190000Z DTSTAMP:20260422T212607Z UID:OSUGGT/23 DESCRIPTION:Title: GKM manifolds - Interactions between combinatorics and topology\nby Pa nagiots Konstantis (Marburg) (Marburg) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nA GKM manifold is a smooth m anifold endowed with a certain type of Torus action. To every GKM manifold s one assigns a combinatorial object\, the GKM graph\, which encodes impor tant properties of the torus action. We discuss how far this object determ ines the topology and the smooth structure of a GKM manifold. This is join t work with Oliver Goertsches and Leopold Zoller.\n LOCATION:https://researchseminars.org/talk/OSUGGT/23/ END:VEVENT BEGIN:VEVENT SUMMARY:David Hume (Bristol) DTSTART:20210202T180000Z DTEND:20210202T190000Z DTSTAMP:20260422T212607Z UID:OSUGGT/24 DESCRIPTION:Title: Coarse Geometry of Groups and Spaces\nby David Hume (Bristol) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nG iven two metric spaces X and Y it is natural to ask how faithfully\, from the point of view of the metric\, one can embed X into Y.\nOne way of maki ng this precise is asking whether there exists a coarse embedding of X int o Y.\n\nPositive results are plentiful and diverse\, from Assouad's embedd ing theorem for doubling metric spaces to the elementary fact that any fin itely generated subgroup of a finitely generated group is coarsely embedde d with respect to word metrics. Moreover\, the consequences of admitting a coarse embedding into a sufficiently nice space can be very strong. By co ntrast\, there are few invariants which provide obstructions to coarse emb eddings\, leaving many elementary geometric questions open.\nI will presen t new families of invariants which resolve some of these questions. In par ticular I will show that the Baumslag-Solitar group BS(m\,n) coarsely embe ds into some hyperbolic group if and only if |m|=|n|=1.\n LOCATION:https://researchseminars.org/talk/OSUGGT/24/ END:VEVENT BEGIN:VEVENT SUMMARY:Teddy Einstein (University of Illinois at Chicago) DTSTART:20210204T180000Z DTEND:20210204T190000Z DTSTAMP:20260422T212607Z UID:OSUGGT/25 DESCRIPTION:Title: Relatively Geometric Actions on CAT(0) Cube Complexes\nby Teddy Einste in (University of Illinois at Chicago) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nThe study of hyperbolic and relatively hyperbolic groups acting on CAT(0) cube complexes has produced exciting recent results in geometric group theory. I will talk about a new kind of action of a relatively hyperbolic group on a CAT(0) cube complex called a relatively geometric action.\nIn joint work with Daniel Groves\, we develop analogues of tools used to construct and study geometric action s of hyperbolic and relatively hyperbolic groups on CAT(0) cube complexes\ , including a relatively geometric version of Agol's Theorem.\nI will also discuss some of the structural theorems we hope to prove and a potential application to the Relative Cannon Conjecture.\n LOCATION:https://researchseminars.org/talk/OSUGGT/25/ END:VEVENT BEGIN:VEVENT SUMMARY:Yash Loda (KIAS) DTSTART:20210209T230000Z DTEND:20210210T000000Z DTSTAMP:20260422T212607Z UID:OSUGGT/26 DESCRIPTION:Title: Spaces of enumerated orderable groups\nby Yash Loda (KIAS) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nAn e numerated group is a group structure on the natural numbers.\nGiven one am ong various notions of orderability of countable groups\, we endow the cla ss of orderable enumerated groups with a Polish topology.\nIn this setting \, we establish a plethora of genericity results using elementary tools fr om Baire category theory and the Grigorchuk space of marked groups.\nIn th is talk I will describe these spaces and some of their striking features.\ nThis is ongoing joint work with Srivatsav Kunnawalkam Elayavalli and Issa c Goldbring.\n LOCATION:https://researchseminars.org/talk/OSUGGT/26/ END:VEVENT BEGIN:VEVENT SUMMARY:Yulan Qing (Fudan University) DTSTART:20210211T180000Z DTEND:20210211T190000Z DTSTAMP:20260422T212607Z UID:OSUGGT/27 DESCRIPTION:Title: Sublinearly Morse Boundary of Groups\nby Yulan Qing (Fudan University) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAb stract\nGromov boundary plays a central role in many aspects of geometric group theory. In this study\, we develop a theory of boundary when the con dition on hyperbolicity is removed: For a given proper\, geodesic metric s pace X and a given sublinear function $\\kappa$\, we define the $\\kappa$- boundary\, as the space of all $\\kappa$-Morse quasi-geodesics rays. The s ublinearly Morse boundary is QI-invariant and thus can be associated with the group that acts geometrically on X. For a large class of groups\, we s how that sublinearly Morse boundaries are large: they provide topological models for the Poisson boundaries of the group. This talk is mainly based on several joint projects with Ilya Gekhtman\, Kasra Rafi and Giulio Tiozz o.\n LOCATION:https://researchseminars.org/talk/OSUGGT/27/ END:VEVENT BEGIN:VEVENT SUMMARY:Roman Sauer (KIT) DTSTART:20210216T180000Z DTEND:20210216T190000Z DTSTAMP:20260422T212607Z UID:OSUGGT/28 DESCRIPTION:Title: Action on Cantor spaces and macroscopic scalar curvature\nby Roman Sau er (KIT) as part of Ohio State Topology and Geometric Group Theory Seminar \n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/OSUGGT/28/ END:VEVENT BEGIN:VEVENT SUMMARY:Stefan Witzel (Giessan) DTSTART:20210225T180000Z DTEND:20210225T190000Z DTSTAMP:20260422T212607Z UID:OSUGGT/29 DESCRIPTION:Title: Uncountably many simple groups up to quasi-isometry\nby Stefan Witzel (Giessan) as part of Ohio State Topology and Geometric Group Theory Semina r\n\n\nAbstract\nThe purpose of geometric group theory is to investigate g roups up to quasi-isometry\, a coarse geometric notion. Many classes of gr oups contain uncountably many finitely generated groups up to isomorphism. From a geometric perspective one is led to ask (for each class) whether this remains true up to quasi-isometry. I will talk about joint work with Ashot Minasyan and Denis Osin where we use the Baire category theorem to a nswer such questions. Specifically I will show that there are uncountably many finitely generated simple groups up to quasi-isometry.\n LOCATION:https://researchseminars.org/talk/OSUGGT/29/ END:VEVENT BEGIN:VEVENT SUMMARY:Makoto Sakuma (Hiroshima U) DTSTART:20210309T233000Z DTEND:20210310T003000Z DTSTAMP:20260422T212607Z UID:OSUGGT/30 DESCRIPTION:Title: Homotopy motions of surfaces in 3-manifolds\nby Makoto Sakuma (Hiroshi ma U) as part of Ohio State Topology and Geometric Group Theory Seminar\n\ n\nAbstract\nWe introduce the concept of a homotopy motion of a subset in a manifold\, and give a systematic study of homotopy motions of surfaces in closed orientable 3-manifolds. This notion arises from various natural problems in 3-manifold theory such as domination of manifold pairs\, homot opical behaviour of simple loops on a Heegaard surface\, and monodromies o f virtual branched covering surface bundles associated to a Heegaard split ting. This is a joint work with Yuya Koda (arXiv:2011.05766).\n LOCATION:https://researchseminars.org/talk/OSUGGT/30/ END:VEVENT BEGIN:VEVENT SUMMARY:Aaron Calderon (Yale University) DTSTART:20210316T170000Z DTEND:20210316T180000Z DTSTAMP:20260422T212607Z UID:OSUGGT/31 DESCRIPTION:Title: Measure laminations and unipotent flows on moduli space\nby Aaron Cald eron (Yale University) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nThere is a deep yet mysterious connection be tween the hyperbolic and singular flat geometry of Riemann surfaces. Using Thurston and Bonahon’s “shear coordinates” for maximal laminations\ , Mirzakhani related the earthquake and horocycle flows on moduli space\, two notions of unipotent flow coming from hyperbolic\, respectively flat\, geometry. In this talk\, I will describe joint work with James Farre in w hich we construct new coordinates for Teichmüller space adapted to any me asured lamination which generalize both Fenchel–Nielsen and shear coordi nates. These coordinates simultaneously parametrize both flat and hyperbol ic structures\, and consequently allow us to extend Mirzakhani’s conjuga cy and gain insight into the ergodic theory of the earthquake flow. If tim e permits\, I will also mention some applications of this result to the eq uidistribution of random hyperbolic surfaces in moduli space.\n LOCATION:https://researchseminars.org/talk/OSUGGT/31/ END:VEVENT BEGIN:VEVENT SUMMARY:Jason Behrstock (City University of New York) DTSTART:20210318T170000Z DTEND:20210318T180000Z DTSTAMP:20260422T212607Z UID:OSUGGT/32 DESCRIPTION:Title: Hierarchically hyperbolic groups: an introduction\nby Jason Behrstock (City University of New York) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nHierarchically hyperbolic spaces prov ide a uniform framework for working with many important examples\, includi ng mapping class groups\, right angled Artin groups\, Teichmuller space\, most cubulated groups\, and others. In this talk I'll provide an introduct ion to studying groups and spaces from this point of view\, both describin g new tools to use to study these groups and applications of those results . This talk will include joint work with Mark Hagen and Alessandro Sisto. \n LOCATION:https://researchseminars.org/talk/OSUGGT/32/ END:VEVENT BEGIN:VEVENT SUMMARY:Stephan Mescher (Leipzig) DTSTART:20210323T170000Z DTEND:20210323T180000Z DTSTAMP:20260422T212607Z UID:OSUGGT/33 DESCRIPTION:by Stephan Mescher (Leipzig) as part of Ohio State Topology an d Geometric Group Theory Seminar\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/OSUGGT/33/ END:VEVENT BEGIN:VEVENT SUMMARY:Andy Putman (Notre Dame) DTSTART:20210325T170000Z DTEND:20210325T180000Z DTSTAMP:20260422T212607Z UID:OSUGGT/34 DESCRIPTION:by Andy Putman (Notre Dame) as part of Ohio State Topology and Geometric Group Theory Seminar\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/OSUGGT/34/ END:VEVENT BEGIN:VEVENT SUMMARY:Hung Cong Tran (University of Oklahoma) DTSTART:20210406T170000Z DTEND:20210406T180000Z DTSTAMP:20260422T212607Z UID:OSUGGT/35 DESCRIPTION:by Hung Cong Tran (University of Oklahoma) as part of Ohio Sta te Topology and Geometric Group Theory Seminar\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/OSUGGT/35/ END:VEVENT BEGIN:VEVENT SUMMARY:Tian-Jun Li (U Minnesota) DTSTART:20210413T170000Z DTEND:20210413T180000Z DTSTAMP:20260422T212607Z UID:OSUGGT/36 DESCRIPTION:by Tian-Jun Li (U Minnesota) as part of Ohio State Topology an d Geometric Group Theory Seminar\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/OSUGGT/36/ END:VEVENT BEGIN:VEVENT SUMMARY:Tim Riley (Cornell) DTSTART:20210415T170000Z DTEND:20210415T180000Z DTSTAMP:20260422T212607Z UID:OSUGGT/37 DESCRIPTION:by Tim Riley (Cornell) as part of Ohio State Topology and Geom etric Group Theory Seminar\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/OSUGGT/37/ END:VEVENT BEGIN:VEVENT SUMMARY:Jim Fowler (OSU) DTSTART:20210420T170000Z DTEND:20210420T180000Z DTSTAMP:20260422T212607Z UID:OSUGGT/38 DESCRIPTION:by Jim Fowler (OSU) as part of Ohio State Topology and Geometr ic Group Theory Seminar\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/OSUGGT/38/ END:VEVENT BEGIN:VEVENT SUMMARY:Nicolas Matte-Bon (Université Lyon 1) DTSTART:20210422T153000Z DTEND:20210422T163000Z DTSTAMP:20260422T212607Z UID:OSUGGT/39 DESCRIPTION:Title: Confined subgroups and highly transitive actions\nby Nicolas Matte-Bon (Université Lyon 1) as part of Ohio State Topology and Geometric Group T heory Seminar\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/OSUGGT/39/ END:VEVENT BEGIN:VEVENT SUMMARY:Rostislav Grigorchuk (Texas A&M) DTSTART:20210304T211500Z DTEND:20210304T221500Z DTSTAMP:20260422T212607Z UID:OSUGGT/40 DESCRIPTION:by Rostislav Grigorchuk (Texas A&M) as part of Ohio State Topo logy and Geometric Group Theory Seminar\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/OSUGGT/40/ END:VEVENT BEGIN:VEVENT SUMMARY:Mitul Islam (Heidelberg University) DTSTART:20211109T152000Z DTEND:20211109T162000Z DTSTAMP:20260422T212607Z UID:OSUGGT/41 DESCRIPTION:Title: Convex co-compact groups and relative hyperbolicity\nby Mitul Islam (H eidelberg University) as part of Ohio State Topology and Geometric Group T heory Seminar\n\n\nAbstract\nThe notion of convex co-compact groups genera lizes convex co-compact Kleinian groups from rank one Lie groups to higher rank Lie groups\, like PGL_d(R) for d at least three. This generalization encompasses many interesting examples coming from Anosov subgroups and no n-Gromov hyperbolic reflection groups. In this talk\, we will discuss a ge ometric property (namely\, strongly isolated simplices) that completely ch aracterizes relatively hyperbolic convex co-compact groups (with periphera l subgroups virtually Abelian of rank at least two). This is joint work wi th Andrew Zimmer.\n LOCATION:https://researchseminars.org/talk/OSUGGT/41/ END:VEVENT END:VCALENDAR