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:20260404T094534Z UID:OSUGGT/1 DESCRIPTION:Title: On Finitely Presented Groups that Contain Q\nby Jim Belk (Univer sity of St Andrews) as part of Ohio State Topology and Geometric Group The ory Seminar\n\n\nAbstract\nIt is a consequence of Higman's embedding theor em that the additive group Q of rational numbers can be embedded into a fi nitely presented group. Though Higman's proof is constructive\, the result ing group 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 finitely presented group that contains an embedded copy of Q. In thi s 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 tha t contains Q. This is joint work with James Hyde and Francesco Matucci.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Johnny Nicholson (University College London) DTSTART:20200714T180000Z DTEND:20200714T190000Z DTSTAMP:20260404T094534Z UID:OSUGGT/2 DESCRIPTION:Title: Projective modules and the homotopy classification of CW-complexes\nby Johnny Nicholson (University College London) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nA basic questio n in the homotopy classification of CW-complexes is to ask for which finit ely presented 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 grou p $G$. Despite early interest by Cockroft-Swan and Dyer-Sieradski\, it was n’t until 1976 that examples of non-cancellation were found by Dunwoody and Metzler. This led Browning to complete the classification in the finit e abelian case. In recent years\, applications to Wall’s D2 problem and the classification of manifolds have sparked renewed interest in this prob lem. In this talk\, we will show how the case where $G$ has periodic cohom ology can largely be reduced to a question about projective $\\mathbb{Z} G $ modules. We then resolve this by generalising results of Swan from the 1 980s.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Mauricio Bustamante (University of Cambridge) DTSTART:20201027T150000Z DTEND:20201027T160000Z DTSTAMP:20260404T094534Z UID:OSUGGT/3 DESCRIPTION:Title: Diffeomorphisms of solid tori\nby Mauricio Bustamante (Universit y of Cambridge) 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 infinit ely generated. 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 p ossible to show that in the range of degrees up to (roughly) d/3\, the hom otopy groups of Diff(T) contain infinitely generated torsion subgroups.\n\ nIn this talk\, I will discuss an alternative point of view to study Diff( T) which does not invoke pseudoisotopy theory: when d=2n\, we interpret Di ff(T) as the "difference" between diffeomorphisms and certain self-embeddi ngs of the manifold X_g obtained as the connected sum of T with the g-fold connected sum of S^n \\times S^n.\n\nWe will see how infinitely generated torsion subgroups appear from this perspective\, and that they can be fou nd even up to degrees d/2. This is ongoing joint work with O. Randal-Willi ams.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Waltraud Lederle (Université Catholique de Louvain) DTSTART:20200827T150000Z DTEND:20200827T160000Z DTSTAMP:20260404T094534Z UID:OSUGGT/4 DESCRIPTION:Title: Conjugacy in Neretin's group\nby Waltraud Lederle (Université C atholique de Louvain) as part of Ohio State Topology and Geometric Group T heory Seminar\n\n\nAbstract\nWe explain when two almost automorphisms of a regular tree are conjugate. Our main focus will be on non-elliptic elemen ts\, where we can use strand diagrams introduced by Belk and Matucci to de scribe conjugacy in Thompson's V. This is joint work with Gil Goffer.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Sam Shepherd (University of Oxford) DTSTART:20200825T150000Z DTEND:20200825T160000Z DTSTAMP:20260404T094534Z UID:OSUGGT/5 DESCRIPTION:Title: Quasi-isometric rigidity of generic cyclic HNN extensions of free gr oups\nby Sam Shepherd (University of Oxford) as part of Ohio State Top ology and Geometric Group Theory Seminar\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Mark Pengitore (OSU) DTSTART:20200610T150000Z DTEND:20200610T160000Z DTSTAMP:20260404T094534Z UID:OSUGGT/7 DESCRIPTION:Title: Coarse embeddings and homological filling functions\nby Mark Pen gitore (OSU) as part of Ohio State Topology and Geometric Group Theory Sem inar\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Benjamin Steinberg (CCNY) DTSTART:20200929T150000Z DTEND:20200929T160000Z DTSTAMP:20260404T094534Z UID:OSUGGT/8 DESCRIPTION:Title: Simplicity of Nekrashevych algebras of contracting self-similar grou ps\nby Benjamin Steinberg (CCNY) as part of Ohio State Topology and Ge ometric Group Theory Seminar\n\n\nAbstract\nA self-similar group is a grou p $G$ acting 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 -similariy of the tree is reflected in the group. The most common examples are generated by the states of a finite automaton. Many famous groups lik e Grigorchuk's 2-group of intermediate growth are of this form.\n\nNekrash evych associated $C^*$-algebras and algebras with coefficients in a field to self-similar groups. In the case $G$ is trivial\, the algebra is the cl assical Leavitt algebra\, a famous finitely presented simple algebra. \n\n Nekrashevych 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. Nekrashev ych then showed that the algebra associated to the Grigorchuk-Erschler gro up is not simple over any field (the first such example). \n\nThe Grigorch uk and Grigorchuk-Erschler groups are contracting self-similar groups. Thi s important class of self-similar groups includes Gupta-Sidki p-groups and many iterated monodromy groups like the Basilica group. Nekrashevych prov ed algebras associated to contacting groups are finitely presented. \n\nIn this talk 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 automaton generating the group. We apply our results to several famili es of contracting groups like Gupta-Sidki groups and Sunic's generalizatio ns of Grigorchuk's group associated to polynomials over finite fields.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Lvzhou Chen (University of Texas-Austin) DTSTART:20200922T150000Z DTEND:20200922T160000Z DTSTAMP:20260404T094534Z UID:OSUGGT/9 DESCRIPTION:Title: Stable commutator lengths of integral chains in right-angled Artin g roups\nby Lvzhou Chen (University of Texas-Austin) as part of Ohio Sta te Topology and Geometric Group Theory Seminar\n\n\nAbstract\nIt follows f rom theorems of Agol and Kahn-Markovic that the fundamental group of any c losed hyperbolic 3-manifold contains a special subgroup of finite index. V ery little is known about how large the index needs to be. Motivated by th is\, in this joint work with Nicolaus Heuer\, we study stable commutator l engths (scl) of integral chains in right-angled Artin groups (RAAGs). Topo logically\, an integral 1-chain in a group G is a collection of loops in t he K(G\,1) space with integral weights\, and its scl is the least complexi ty of surfaces bounding the weighted loops. We show that the infimal posit ive scl of integral chains in any RAAG is positive\, and its size explicit ly depends on the defining graph of the RAAG up to a multiplicative consta nt 12. In particular\, the size is non-uniform among RAAGs\, which is unex pected.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Laurent Bartholdi (Goettingen) DTSTART:20201015T150000Z DTEND:20201015T160000Z DTSTAMP:20260404T094534Z UID:OSUGGT/10 DESCRIPTION:Title: Domino problems on graphs and groups\nby Laurent Bartholdi (Goe ttingen) as part of Ohio State Topology and Geometric Group Theory Seminar \n\n\nAbstract\nFor a fixed edge-labelled graph\, the "domino problem" ask s: "given a collection of labelled dominoes (with numbers on their ends)\, can one 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 problem is deeply connected to (monadic\, second-order) logic\; remar kably\, it is undecidable for graphs such as the infinite square grid – the "Wang 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 example s not containing grids yet also having undecidable domino problem.\n\nPart of this is joint work with Ville Salo.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Ilir Snopce (Rio de Janeiro) DTSTART:20201203T160000Z DTEND:20201203T170000Z DTSTAMP:20260404T094534Z UID:OSUGGT/13 DESCRIPTION:Title: Retracts in free groups\nby Ilir Snopce (Rio de Janeiro) as par t of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\ nA subgroup R of a group G is said to be a retract of G if there is a homo morphism r : G → R that restricts to the identity on R. I will talk abou t retracts in free groups. In particular\, I will discuss the following qu estion raised by Bergman: Let F be a free group of finite rank and let R b e a retract of F. Is it H ∩ R is a retract of H for every finitely gene rated subgroup H of F? \n\nThis talk is based on a joint work with Sloboda n Tanushevski and Pavel Zalesskii.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Marcin Sabok (McGill University) DTSTART:20191105T160000Z DTEND:20191105T170000Z DTSTAMP:20260404T094534Z UID:OSUGGT/15 DESCRIPTION:Title: Hyperfiniteness at Gromov boundaries\nby Marcin Sabok (McGill U niversity) as part of Ohio State Topology and Geometric Group Theory Semin ar\n\n\nAbstract\nI will discuss recent results establishing hyperfinitene ss of equivalence relations induced by actions on Gromov boundaries of var ious hyperbolic spaces. This includes boundary actions of hyperbolic group s (joint work with T. Marquis) and actions of the mapping class group on b oundaries of the arc graph and the curve graph (joint work with P. Przytyc ki)\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Alex Margolis (Vanderbilt University) DTSTART:20201110T160000Z DTEND:20201110T170000Z DTSTAMP:20260404T094534Z UID:OSUGGT/16 DESCRIPTION:Title: Topological completions of quasi-actions and discretisable spaces\nby Alex Margolis (Vanderbilt University) as part of Ohio State Topolog y and Geometric Group Theory Seminar\n\n\nAbstract\nA fundamental problem in geometric group theory is the\nstudy of quasi-actions. We introduce an d investigate discretisable\nspaces: spaces for which every cobounded quas i-action can be\nquasi-conjugated to an isometric action on a locally fini te graph. Work\nof Mosher-Sageev-Whyte shows that non-abelian free groups are\ndiscretisable\, but the property holds much more generally. For insta nce\,\nevery non-elementary hyperbolic group that is not virtually isomorp hic\nto a cocompact lattice in rank one Lie group is discretisable.\n\nAlo ng the way\, we study the coarse geometry of groups containing almost\nnor mal/commensurated subgroups\, and we introduce the concept of the\ntopolog ical completion of a quasi-action. The topological completion is\na locall y compact group\, well-defined up to a compact normal subgroup\,\nreflecti ng the geometry of the quasi-action. We give several\napplications of the tools we develop. For instance we show that any\nfinitely generated group quasi-isometric to a ‬Z‭-by-hyperbolic group is\nalso Z-by-hyperbolic\ , and prove quasi-isometric rigidity for a large\nclass of right-angled Ar tin groups.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Xiaolei Wu (Bielefeld University) DTSTART:20201117T160000Z DTEND:20201117T170000Z DTSTAMP:20260404T094534Z UID:OSUGGT/17 DESCRIPTION:Title: On the poly-freeness of Artin groups\nby Xiaolei Wu (Bielefeld University) as part of Ohio State Topology and Geometric Group Theory Semi nar\n\n\nAbstract\nArtin group is an important class of groups under inten sive study in recent years. It is a generalization of the braid groups. Be stvina asks whether all Artin groups are virtually poly-free. In this talk \, we first give an introduction to poly-free groups and Artin groups. We explain some connections with the Farrell-Jones Conjecture. Then we explai n some recent progress of Bestvina's question. In particular\, we will giv e a short 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://stable.researchseminars.org/talk/OSUGGT/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Woodhouse (University of Oxford) DTSTART:20201119T160000Z DTEND:20201119T170000Z DTSTAMP:20260404T094534Z UID:OSUGGT/18 DESCRIPTION:Title: Action rigidity of free products of hyperbolic manifold groups\ nby Daniel Woodhouse (University of Oxford) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nGromov's program for un derstanding finitely generated groups up to their large scale geometry con siders three possible relations: quasi-isometry\, abstract commensurabilit y\, and acting geometrically on the same proper geodesic metric space. A * common model geometry* for groups G and G' is a proper geodesic metric spa ce on which 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 commensura ble to G. We show that free products of closed hyperbolic surface or 3-man ifold groups are action rigid. As a corollary\, we obtain torsion-free\, G romov hyperbolic groups that are quasi-isometric\, but do not even virtual ly act on the same proper geodesic metric space.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Christoforos Neofytidis (Ohio State University) DTSTART:20210112T180000Z DTEND:20210112T190000Z DTSTAMP:20260404T094534Z UID:OSUGGT/19 DESCRIPTION:Title: Endomorphisms of mapping tori\nby Christoforos Neofytidis (Ohio State University) as part of Ohio State Topology and Geometric Group Theo ry Seminar\n\n\nAbstract\nOne of the most fundamental results in 3-dimensi onal topology\, proved in works of Gromov\, Mostow\, Wang and Waldhausen\, is that any self-map of non-zero degree of a mapping torus of a closed hy perbolic surface is homotopic to a homeomorphism if and only if the monodr omy is not periodic. Key properties for the proof were the existence of hy perbolic 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 wit h a corresponding higher dimensional aspherical manifold. More generally\, we will classify in terms of Hopf-type properties mapping tori of residua lly finite Poincaré Duality groups with non-zero Euler characteristic. It turns out that the rigidity behavior of these mapping tori with trivial c enter is similar to that of non-elementary torsion-free hyperbolic groups. \n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Mike Davis (Ohio State University) DTSTART:20210119T180000Z DTEND:20210119T190000Z DTSTAMP:20260404T094534Z UID:OSUGGT/20 DESCRIPTION:Title: Bordifications of hyperplane arrangement complements and curve comp lexes of spherical Artin groups\nby Mike Davis (Ohio State University) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAb stract\nThe complement of an arrangement of hyperplanes in a complex vecto r space has a natural bordification to a manifold with corners formed by r emoving tubular neighborhoods of the hyperplanes and certain of their inte rsections. When the arrangement is the complexification of a real simplic ial arrangement\, the bordification closely resembles Harvey's bordificati on of the braid group. The faces of the universal cover of the bordifica tion are parameterized by the simplices of a simplicial complex\, the vert ices of which are the irreducible ``parabolic subgroups'' of the fundament al group of the arrangement complement. When the arrangement is associated to a finite reflection group\, we get the "curve complex" of the associat ed pure Artin group. In analogy with curve complexes for mapping class gro ups and with spherical buildings\, our curve complex has the homotopy type of a wedge of spheres. This is joint work with Jingyin Huang.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Berlyne (City University of New York) DTSTART:20210121T180000Z DTEND:20210121T190000Z DTSTAMP:20260404T094534Z UID:OSUGGT/21 DESCRIPTION:Title: Graph products as hierarchically hyperbolic groups\nby Daniel B erlyne (City University of New York) as part of Ohio State Topology and Ge ometric Group Theory Seminar\n\n\nAbstract\nGiven a finite simplicial grap h with a finitely generated group associated to each vertex\, the graph pr oduct is defined by taking the free product of the vertex groups and addin g commutation relations between elements belonging to vertex groups that a re connected by a edge in the graph. Common examples of graph products inc lude right-angled Artin groups (where all vertex groups are Z) and right-a ngled Coxeter groups (where all vertex groups are Z/2Z). Behrstock\, Hagen \, and Sisto showed that right-angled Artin groups exhibit a notion of non -positive curvature called hierarchical hyperbolicity\, with deep geometri c consequences such as a Masur-Minsky style distance formula\, finite asym ptotic dimension\, and acylindrical hyperbolicity. By developing analogues of the cubical techniques employed by Behrstock-Hagen-Sisto\, we are able to generalise their result\, showing that any graph product with hierarch ically hyperbolic vertex groups is itself a hierarchically hyperbolic grou p. In doing so\, we answer two questions of Behrstock-Hagen-Sisto and two questions of Genevois. This is joint work with Jacob Russell.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Francis Wagner (Vanderbilt) DTSTART:20210126T180000Z DTEND:20210126T190000Z DTSTAMP:20260404T094534Z UID:OSUGGT/22 DESCRIPTION:Title: Torsion Subgroups of Groups with Quadratic Dehn Function\nby Fr ancis Wagner (Vanderbilt) as part of Ohio State Topology and Geometric Gro up Theory Seminar\n\n\nAbstract\nThe Dehn function of a finitely presented group\, first introduced by Gromov\, is a useful invariant that is closel y related to the solvability of the group’s word problem. It is well-kno wn that a finitely presented group is word hyperbolic if and only if it ha s sub-quadratic (and thus linear) Dehn function. A result of Ghys and de l a Harpe states that no word hyperbolic group can have a (finitely generate d) infinite torsion subgroup. We show that this property does not carry ov er to any class of groups of larger Dehn function. In particular\, for eve ry m>1 and n sufficiently large (and either odd or divisible by 2^9)\, the re exists 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://stable.researchseminars.org/talk/OSUGGT/22/ END:VEVENT BEGIN:VEVENT SUMMARY:Panagiots Konstantis (Marburg) (Marburg) DTSTART:20210128T180000Z DTEND:20210128T190000Z DTSTAMP:20260404T094534Z UID:OSUGGT/23 DESCRIPTION:Title: GKM manifolds - Interactions between combinatorics and topology \nby Panagiots Konstantis (Marburg) (Marburg) as part of Ohio State Topolo gy and Geometric Group Theory Seminar\n\n\nAbstract\nA GKM manifold is a s mooth manifold endowed with a certain type of Torus action. To every GKM m anifolds one assigns a combinatorial object\, the GKM graph\, which encode s important properties of the torus action. We discuss how far this object determines the topology and the smooth structure of a GKM manifold. This is joint work with Oliver Goertsches and Leopold Zoller.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/23/ END:VEVENT BEGIN:VEVENT SUMMARY:David Hume (Bristol) DTSTART:20210202T180000Z DTEND:20210202T190000Z DTSTAMP:20260404T094534Z UID:OSUGGT/24 DESCRIPTION:Title: Coarse Geometry of Groups and Spaces\nby David Hume (Bristol) a s part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbst ract\nGiven 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 making this precise is asking whether there exists a coarse embedding o f X into Y.\n\nPositive results are plentiful and diverse\, from Assouad's embedding theorem for doubling metric spaces to the elementary fact that any finitely generated subgroup of a finitely generated group is coarsely embedded with respect to word metrics. Moreover\, the consequences of admi tting a coarse embedding into a sufficiently nice space can be very strong . By contrast\, there are few invariants which provide obstructions to coa rse embeddings\, leaving many elementary geometric questions open.\nI will present new families of invariants which resolve some of these questions. In particular I will show that the Baumslag-Solitar group BS(m\,n) coarse ly embeds into some hyperbolic group if and only if |m|=|n|=1.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/24/ END:VEVENT BEGIN:VEVENT SUMMARY:Teddy Einstein (University of Illinois at Chicago) DTSTART:20210204T180000Z DTEND:20210204T190000Z DTSTAMP:20260404T094534Z UID:OSUGGT/25 DESCRIPTION:Title: Relatively Geometric Actions on CAT(0) Cube Complexes\nby Teddy Einstein (University of Illinois at Chicago) as part of Ohio State Topolo gy and Geometric Group Theory Seminar\n\n\nAbstract\nThe study of hyperbol ic and relatively hyperbolic groups acting on CAT(0) cube complexes has pr oduced exciting recent results in geometric group theory. I will talk abou t a new kind of action of a relatively hyperbolic group on a CAT(0) cube c omplex called a relatively geometric action.\nIn joint work with Daniel Gr oves\, we develop analogues of tools used to construct and study geometric actions of hyperbolic and relatively hyperbolic groups on CAT(0) cube com plexes\, including a relatively geometric version of Agol's Theorem.\nI wi ll also discuss some of the structural theorems we hope to prove and a pot ential application to the Relative Cannon Conjecture.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/25/ END:VEVENT BEGIN:VEVENT SUMMARY:Yash Loda (KIAS) DTSTART:20210209T230000Z DTEND:20210210T000000Z DTSTAMP:20260404T094534Z UID:OSUGGT/26 DESCRIPTION:Title: Spaces of enumerated orderable groups\nby Yash Loda (KIAS) as p art of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstrac t\nAn enumerated group is a group structure on the natural numbers.\nGiven one among various notions of orderability of countable groups\, we endow the class of orderable enumerated groups with a Polish topology.\nIn this setting\, we establish a plethora of genericity results using elementary t ools from Baire category theory and the Grigorchuk space of marked groups. \nIn this talk I will describe these spaces and some of their striking fea tures.\nThis is ongoing joint work with Srivatsav Kunnawalkam Elayavalli a nd Issac Goldbring.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/26/ END:VEVENT BEGIN:VEVENT SUMMARY:Yulan Qing (Fudan University) DTSTART:20210211T180000Z DTEND:20210211T190000Z DTSTAMP:20260404T094534Z UID:OSUGGT/27 DESCRIPTION:Title: Sublinearly Morse Boundary of Groups\nby Yulan Qing (Fudan Univ ersity) as part of Ohio State Topology and Geometric Group Theory Seminar\ n\n\nAbstract\nGromov boundary plays a central role in many aspects of geo metric group theory. In this study\, we develop a theory of boundary when the condition on hyperbolicity is removed: For a given proper\, geodesic m etric space X and a given sublinear function $\\kappa$\, we define the $\\ kappa$-boundary\, as the space of all $\\kappa$-Morse quasi-geodesics rays . The sublinearly Morse boundary is QI-invariant and thus can be associate d with the group that acts geometrically on X. For a large class of groups \, we show that sublinearly Morse boundaries are large: they provide topol ogical models for the Poisson boundaries of the group. This talk is mainly based on several joint projects with Ilya Gekhtman\, Kasra Rafi and Giuli o Tiozzo.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/27/ END:VEVENT BEGIN:VEVENT SUMMARY:Roman Sauer (KIT) DTSTART:20210216T180000Z DTEND:20210216T190000Z DTSTAMP:20260404T094534Z UID:OSUGGT/28 DESCRIPTION:Title: Action on Cantor spaces and macroscopic scalar curvature\nby Ro man Sauer (KIT) as part of Ohio State Topology and Geometric Group Theory Seminar\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/28/ END:VEVENT BEGIN:VEVENT SUMMARY:Stefan Witzel (Giessan) DTSTART:20210225T180000Z DTEND:20210225T190000Z DTSTAMP:20260404T094534Z 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 Seminar\n\n\nAbstract\nThe purpose of geometric group theory is to invest igate groups up to quasi-isometry\, a coarse geometric notion. Many classe s of groups contain uncountably many finitely generated groups up to isomo rphism. From a geometric perspective one is led to ask (for each class) w hether this remains true up to quasi-isometry. I will talk about joint wor k with Ashot Minasyan and Denis Osin where we use the Baire category theor em to answer such questions. Specifically I will show that there are uncou ntably many finitely generated simple groups up to quasi-isometry.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/29/ END:VEVENT BEGIN:VEVENT SUMMARY:Makoto Sakuma (Hiroshima U) DTSTART:20210309T233000Z DTEND:20210310T003000Z DTSTAMP:20260404T094534Z UID:OSUGGT/30 DESCRIPTION:Title: Homotopy motions of surfaces in 3-manifolds\nby Makoto Sakuma ( Hiroshima U) as part of Ohio State Topology and Geometric Group Theory Sem inar\n\n\nAbstract\nWe introduce the concept of a homotopy motion of a sub set in a manifold\, and give a systematic study of homotopy motions of su rfaces in closed orientable 3-manifolds. This notion arises from various n atural problems in 3-manifold theory such as domination of manifold pairs\ , homotopical behaviour of simple loops on a Heegaard surface\, and monodr omies of virtual branched covering surface bundles associated to a Heegaar d splitting. This is a joint work with Yuya Koda (arXiv:2011.05766).\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/30/ END:VEVENT BEGIN:VEVENT SUMMARY:Aaron Calderon (Yale University) DTSTART:20210316T170000Z DTEND:20210316T180000Z DTSTAMP:20260404T094534Z UID:OSUGGT/31 DESCRIPTION:Title: Measure laminations and unipotent flows on moduli space\nby Aar on Calderon (Yale University) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nThere is a deep yet mysterious connec tion between the hyperbolic and singular flat geometry of Riemann surfaces . Using Thurston and Bonahon’s “shear coordinates” for maximal lamin ations\, Mirzakhani related the earthquake and horocycle flows on moduli s pace\, two notions of unipotent flow coming from hyperbolic\, respectively flat\, geometry. In this talk\, I will describe joint work with James Far re in which we construct new coordinates for Teichmüller space adapted to any measured lamination which generalize both Fenchel–Nielsen and shear coordinates. These coordinates simultaneously parametrize both flat and h yperbolic structures\, and consequently allow us to extend Mirzakhani’s conjugacy and gain insight into the ergodic theory of the earthquake flow. If time permits\, I will also mention some applications of this result to the equidistribution of random hyperbolic surfaces in moduli space.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/31/ END:VEVENT BEGIN:VEVENT SUMMARY:Jason Behrstock (City University of New York) DTSTART:20210318T170000Z DTEND:20210318T180000Z DTSTAMP:20260404T094534Z UID:OSUGGT/32 DESCRIPTION:Title: Hierarchically hyperbolic groups: an introduction\nby Jason Beh rstock (City University of New York) as part of Ohio State Topology and Ge ometric Group Theory Seminar\n\n\nAbstract\nHierarchically hyperbolic spac es provide a uniform framework for working with many important examples\, including mapping class groups\, right angled Artin groups\, Teichmuller s pace\, most cubulated groups\, and others. In this talk I'll provide an in troduction to studying groups and spaces from this point of view\, both de scribing 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://stable.researchseminars.org/talk/OSUGGT/32/ END:VEVENT BEGIN:VEVENT SUMMARY:Stephan Mescher (Leipzig) DTSTART:20210323T170000Z DTEND:20210323T180000Z DTSTAMP:20260404T094534Z 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://stable.researchseminars.org/talk/OSUGGT/33/ END:VEVENT BEGIN:VEVENT SUMMARY:Andy Putman (Notre Dame) DTSTART:20210325T170000Z DTEND:20210325T180000Z DTSTAMP:20260404T094534Z 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://stable.researchseminars.org/talk/OSUGGT/34/ END:VEVENT BEGIN:VEVENT SUMMARY:Hung Cong Tran (University of Oklahoma) DTSTART:20210406T170000Z DTEND:20210406T180000Z DTSTAMP:20260404T094534Z 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://stable.researchseminars.org/talk/OSUGGT/35/ END:VEVENT BEGIN:VEVENT SUMMARY:Tian-Jun Li (U Minnesota) DTSTART:20210413T170000Z DTEND:20210413T180000Z DTSTAMP:20260404T094534Z 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://stable.researchseminars.org/talk/OSUGGT/36/ END:VEVENT BEGIN:VEVENT SUMMARY:Tim Riley (Cornell) DTSTART:20210415T170000Z DTEND:20210415T180000Z DTSTAMP:20260404T094534Z 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://stable.researchseminars.org/talk/OSUGGT/37/ END:VEVENT BEGIN:VEVENT SUMMARY:Jim Fowler (OSU) DTSTART:20210420T170000Z DTEND:20210420T180000Z DTSTAMP:20260404T094534Z 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://stable.researchseminars.org/talk/OSUGGT/38/ END:VEVENT BEGIN:VEVENT SUMMARY:Nicolas Matte-Bon (Université Lyon 1) DTSTART:20210422T153000Z DTEND:20210422T163000Z DTSTAMP:20260404T094534Z UID:OSUGGT/39 DESCRIPTION:Title: Confined subgroups and highly transitive actions\nby Nicolas Ma tte-Bon (Université Lyon 1) as part of Ohio State Topology and Geometric Group Theory Seminar\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/39/ END:VEVENT BEGIN:VEVENT SUMMARY:Rostislav Grigorchuk (Texas A&M) DTSTART:20210304T211500Z DTEND:20210304T221500Z DTSTAMP:20260404T094534Z 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://stable.researchseminars.org/talk/OSUGGT/40/ END:VEVENT BEGIN:VEVENT SUMMARY:Mitul Islam (Heidelberg University) DTSTART:20211109T152000Z DTEND:20211109T162000Z DTSTAMP:20260404T094534Z UID:OSUGGT/41 DESCRIPTION:Title: Convex co-compact groups and relative hyperbolicity\nby Mitul I slam (Heidelberg University) as part of Ohio State Topology and Geometric Group Theory Seminar\n\n\nAbstract\nThe notion of convex co-compact groups generalizes 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 general ization encompasses many interesting examples coming from Anosov subgroups and non-Gromov hyperbolic reflection groups. In this talk\, we will discu ss a geometric property (namely\, strongly isolated simplices) that comple tely characterizes relatively hyperbolic convex co-compact groups (with pe ripheral subgroups virtually Abelian of rank at least two). This is joint work with Andrew Zimmer.\n LOCATION:https://stable.researchseminars.org/talk/OSUGGT/41/ END:VEVENT END:VCALENDAR