BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Johannes Ebert (University of Münster) DTSTART:20200512T140000Z DTEND:20200512T150000Z DTSTAMP:20260404T094802Z UID:GoeTop/1 DESCRIPTION:Title: On the homotopy type of the space of metrics of positive scalar curv ature\nby Johannes Ebert (University of Münster) as part of Göttinge n topology and geometry seminar\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Georg Frenck (Karlsruhe Institute of Technology) DTSTART:20200519T123000Z DTEND:20200519T133000Z DTSTAMP:20260404T094802Z UID:GoeTop/3 DESCRIPTION:Title: H-space structures on spaces of metrics of positive scalar curvature \nby Georg Frenck (Karlsruhe Institute of Technology) as part of Gött ingen topology and geometry seminar\n\n\nAbstract\nWe construct and study an $H$-space multiplication on $\\mathcal{R}^+(M)$ for simply connected Sp in-manifolds $M$ which are Spin-nullcobordant. This will lead to a form of computation called "graphical calculus" which is the used to derive a rig idity criterion for the action of the diffeomorphism group on $\\mathcal{R }^+(M)$ via pullback. We will also indicate\, how to get rid of the assump tion of being simply connected and Spin.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Saskia Roos (University of Potsdam) DTSTART:20200526T123000Z DTEND:20200526T133000Z DTSTAMP:20260404T094802Z UID:GoeTop/4 DESCRIPTION:Title: The chiral anomaly of the free Fermion in functorial field theory\nby Saskia Roos (University of Potsdam) as part of Göttingen topology a nd geometry seminar\n\n\nAbstract\nWhen trying to cast the free fermion in the framework of functorial field theory\, its chiral anomaly manifests i n the fact that it assigns the determinant of the Dirac operator to a top- dimensional closed spin manifold\, which is not a number as expected\, but an element of a complex line. In functorial field theory language\, this means that the theory is twisted\, which gives rise to an anomaly theory. In this talk\, we give a detailed construction of this anomaly theory\, as a functor that sends manifolds to infinite-dimensional Clifford algebras and bordisms to bimodules.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Jinmin Wang (Shanghai Center for Mathematical Sciences) DTSTART:20200602T143000Z DTEND:20200602T153000Z DTSTAMP:20260404T094802Z UID:GoeTop/5 DESCRIPTION:Title: Approximation of delocalized eta invariants by their finite analogue s\nby Jinmin Wang (Shanghai Center for Mathematical Sciences) as part of Göttingen topology and geometry seminar\n\n\nAbstract\nThe delocalized eta invariant for self-adjoint elliptic operators was introduced by Lott as a natural extension of the classical eta invariant of Atiyah-Patodi-Sin ger. In this talk\, we will give several results on when the delocalized e ta invariant can be approximated by the ones associated with finite-sheete d covering spaces\, under a necessary assumption of conjugacy distinguisha bility. In the first part\, we will present a result using a K-theoretical approach of the delocalized eta invariant. In the second part\, we will g ive a quantized description of conjugacy distinguishability. This is a joi nt work with Zhizhang Xie and Guoliang Yu.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Benjamin Waßermann (Karlsruhe Institute of Technology) DTSTART:20200623T143000Z DTEND:20200623T153000Z DTSTAMP:20260404T094802Z UID:GoeTop/6 DESCRIPTION:Title: The $L^2$-Cheeger Müller Theorem and its applications to hyperbolic lattices\nby Benjamin Waßermann (Karlsruhe Institute of Technology) as part of Göttingen topology and geometry seminar\n\n\nAbstract\nIn this talk\, we examine the relationship in different contexts between the anal ytic and the topological $L^2$-torsion of odd-dimensional manifolds. \n\nL et $M$ be a compact\, smooth\, odd-dimensional manifold-with-boundary sati sfying $\\chi(M) = 0$ and let $\\rho \\colon \\pi_1(M) \\to \\GL(V)$ be a finite-dimensional unimodular representation of its fundamental group. Pro vided that the pair $(M\,\\rho)$ is $L^2$-acyclic and a technical determin ant class condition is satisfied\, two positive real numbers $T_{An}^{(2)} (M\,\\rho)\,T_{Top}^{(2)}(M\,\\rho)$\, the analytic and topological $L^2$- torsion of $(M\,\\rho)$\, can be defined. \n\nWhile $T_{Top}^{(2)}(M\,\\rh o)$ is constructed solely with the aid of any arbitrary CW-structure on $M $\, a Riemannian metric on $M$ as well as a metric on the flat bundle $E_\ \rho \\downarrow M$ associated to $\\rho$ is needed to defined $T_{An}^{(2 )}(M\,\\rho)$.\n\nThe first part of this talk is devoted to present a rece nt result\, which establishes the relationship between the two quantities and from which follows that they agree in many instances. \n\nIn the secon d part\, we will consider odd-dimensional hyperbolic manifolds of finite v olume (in particular\, not necessarily compact spaces) and representations of the ambient Lie group. In this instance\, another recent result is pre sented which extends the definition of $T_{An}^{(2)}(M\,\\rho)$ and $T_{To p}^{(2)}(M\,\\rho)$ and shows the equality of the two quantities in this c ase.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Paolo Antonini (SISSA Trieste) DTSTART:20200609T123000Z DTEND:20200609T133000Z DTSTAMP:20260404T094802Z UID:GoeTop/7 DESCRIPTION:Title: The Baum–Connes conjecture localised at the unit element of a disc rete group\nby Paolo Antonini (SISSA Trieste) as part of Göttingen to pology and geometry seminar\n\n\nAbstract\nLet Γ be a discrete group\; we construct a Baum–Connes map localised at the\nunit element of Γ. This is an assembly map in KK–theory with real coefficients\nleading to a for m of the Baum–Connes conjecture which is intermediate between\nthe Baum –Connes conjecture and the Strong Novikov conjecture.\nThe localised ass embly map has an interesting property: it is functorial with\nrespect to g roup morphisms.\nWe explain the construction and we show that the relation with the Novikov\nconjecture follows from a comparison at the level of KK R-theory of the classifying space for free and proper actions EΓ with the classifying space for proper\nactions EΓ.\nBased on joint work with Sara Azzali and Georges Skandalis.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Demetre Kazaras (Stony Brook University) DTSTART:20200616T143000Z DTEND:20200616T153000Z DTSTAMP:20260404T094802Z UID:GoeTop/8 DESCRIPTION:Title: Scalar curvature\, mass\, and harmonic maps\nby Demetre Kazaras (Stony Brook University) as part of Göttingen topology and geometry semin ar\n\n\nAbstract\nFor a 3-dimensional Riemannian manifold there is a relat ionship between the level sets of a harmonic map and the manifold's scalar curvature\, expressed by a formula discovered by Daniel Stern. New proofs of classical facts in the study of scalar curvature can be given with thi s formula. We adopt this harmonic map perspective to give novel bounds for the mass of asymptotically flat initial data sets in terms of certain asy mptotically linear functions. As a consequence\, we obtain a new proof of the space-time Positive Mass Theorem in dimension 3. These results are joi nt work with Hugh Bray\, Sven Hirsch\, Marcus Khuri\, and Daniel Stern.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Jian Wang (University of Augsburg) DTSTART:20200714T143000Z DTEND:20200714T153000Z DTSTAMP:20260404T094802Z UID:GoeTop/9 DESCRIPTION:Title: Contractible 3-manifolds and Positive scalar curvature\nby Jian Wang (University of Augsburg) as part of Göttingen topology and geometry seminar\n\n\nAbstract\nIt is unknown that a contractible 3-manifold has a complete metric with positive scalar curvature. The topology of contractib le 3-manifolds is much complicated. For example\, the Whitehead manifold i s a contractible 3-manifold but not homeomorphic to $\\mathbb{R}^3$. In th is talk\, we will present the proof that it has no complete metric with po sitive scalar curvature. We will further explain that a complete contracti ble 3-manifold with positive scalar curvature and trivial fundamental grou p at infinity is homeomorphic to $\\mathbb{R}^3$.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Ulrich Bunke (University of Regensburg) DTSTART:20200804T123000Z DTEND:20200804T133000Z DTSTAMP:20260404T094802Z UID:GoeTop/10 DESCRIPTION:Title: Spectrum-valued $\\mathrm{KK}^G$\, Paschke duality and assembly map s\nby Ulrich Bunke (University of Regensburg) as part of Göttingen to pology and geometry seminar\n\n\nAbstract\nI will explain a version of Pas chke-duality which connects the usual equivariant analytic $\\mathrm{K}$-h omology theory with the equivariant $\\mathrm{K}$-homology theory derived from equivariant coarse $\\mathrm{K}$-homology. The Davis-Lück assembly m ap can be expressed through the coarse homology theory. Using Paschke dua lity we identify it with the classical version of the Baum-Connes assembly map via descent and Kasparov’s projection. All this will be phrased usi ng a spectrum-valued $\\mathrm{KK}^G$-theory\, and we allow coefficients i n $\\mathrm{C}^\\ast$-categories with $G$-action.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Tom Dove (University of Göttingen) DTSTART:20201110T131500Z DTEND:20201110T144500Z DTSTAMP:20260404T094802Z UID:GoeTop/11 DESCRIPTION:Title: Twisted Equivariant Tate K-Theory\nby Tom Dove (University of G öttingen) as part of Göttingen topology and geometry seminar\n\n\nAbstra ct\nEquivariant Tate K-theory is an equivariant cohomology theory built on the K-theory of orbifold loop spaces. I’ll introduce the construction o f this theory\, in particular the loop groupoid\, which serves as an equiv ariant analogue of the free loop space. After this I will describe the mai n purpose of my masters thesis: constructing a twisted version of equivari ant Tate K-theory.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Schick (University of Göttingen) DTSTART:20201117T131500Z DTEND:20201117T144500Z DTSTAMP:20260404T094802Z UID:GoeTop/12 DESCRIPTION:Title: Flexibility and Rigidity of Lipschitz Riemannian Geometry\nby T homas Schick (University of Göttingen) as part of Göttingen topology and geometry seminar\n\n\nAbstract\nEvery smooth isometric embedding of the 2 -sphere into\n$\\mathbb{R}^3$ the standard one (upto rotations\, translati ons\, and reflections).\n\nIn contrast to this classical rigidity result w e have flexibility:\nThere are Lipschitz isometric embeddings of the 2-sph ere in $\\mathbb{R}^3$ whose image\nhas arbitrarily small diameter.\n\nThe talk will present more of these surprising flexibility results for\nLipsc hitz maps between Riemannian manifolds.\n\nEventually\, our focus will be on the following rigidity result of Llarull:\n\nlet $f\\colon M \\to S^n$ be a smooth map between a compact Riemannian manifold M and\nS^n with the standard metric. If M is sufficiently curved (scalar\ncurvature is everywh ere >= the scalar curvature of $S^n$)\, if the map is\nnon-expanding (Lips chitz constant <=1) and if it is far enough from a constant\nmap (has non- zero degree) then f must be an isometry.\n\nWe will discuss the ideas of t he proof\, which involve the geometry of vector\nbundles\, and Gromov's qu estion whether rigidity prevails or flexibility occurs\nif just have Lipsc hitz continuity in the setup of the above theorem.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Thorsten Hertl (University of Göttingen) DTSTART:20201124T131500Z DTEND:20201124T144500Z DTSTAMP:20260404T094802Z UID:GoeTop/13 DESCRIPTION:Title: Cubical Models for Positive Scalar Curvature\nby Thorsten Hertl (University of Göttingen) as part of Göttingen topology and geometry se minar\n\n\nAbstract\nThe space of all positive scalar curvature metrics $R ^+(M)$ has attracted a lot \nof attention during the last decades. Despite that\, (almost) all approaches to gain\ninformations rely heavily on meth ods coming from index theory. \nDue to its concordance invariance\, we pro pose another space to study which only \nencoded concordance information i n its nature.\nWe will then present an attempt to factorise the index diff erence over this space.\nThis project is part of my ongoing Ph.D. thesis a nd is work in progress.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Markus Hausmann (University of Bonn) DTSTART:20201201T131500Z DTEND:20201201T144500Z DTSTAMP:20260404T094802Z UID:GoeTop/14 DESCRIPTION:Title: Complex bordism and the equivariant Quillen theorem\nby Markus Hausmann (University of Bonn) as part of Göttingen topology and geometry seminar\n\n\nAbstract\nIn 1969\, Quillen showed that the formal group law of complex bordism is the\nuniversal one\, and hence the complex bordism r ing is isomorphic to the Lazard\nring. In my talk I will first recall this classical story and then discuss an\nequivariant version of Quillen’s t heorem\, over a fixed abelian group and in a\nglobal equivariant setting.\ n LOCATION:https://stable.researchseminars.org/talk/GoeTop/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Andreas Wagenblast (University of Göttingen) DTSTART:20201208T131500Z DTEND:20201208T144500Z DTSTAMP:20260404T094802Z UID:GoeTop/15 DESCRIPTION:Title: Topology of spaces of loops\nby Andreas Wagenblast (University of Göttingen) as part of Göttingen topology and geometry seminar\n\n\nAb stract\nIn my talk I will start with a brief introduction to configuration spaces and some basic results (e.g. the natural projection $PB_n\\to PB_{ n-1}$\, by forgetting the $n$-th puncture\, is known to be a fibration. Th is fact is no longer true for the pure untwisted rings/wickets). After tha t I want to explain the geometric method of Brendle and Hatcher\, explaine d in their 2010 paper titled *Configuration Spaces of Rings and Wickets* f or computing some of the fundamental groups and demonstrate this on some e xamples. There is\, however\, a limitation of this procedure\, i.e. the me thod does not imediately apply to *pure untwisted wickets*. In the last pa rt of my talk I will point out this problem and indicate a (hopefully poss ible) solution to this\, which (if it works out) in the end will be some o f my results of my master thesis.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Marc Kegel (Humboldt University Berlin) DTSTART:20210126T131500Z DTEND:20210126T144500Z DTSTAMP:20260404T094802Z UID:GoeTop/16 DESCRIPTION:Title: Characterizing slopes for Legendrian knots\nby Marc Kegel (Humb oldt University Berlin) as part of Göttingen topology and geometry semina r\n\n\nAbstract\nCharacterizing slopes for Legendrian knots:\nFrom a given Legendrian knot K in the standard contact 3-sphere\, we can construct a s ymplectic 4-manifold W_K by attaching a Weinstein 2-handle along K to the 4-ball. In this talk\, we will construct non-equivalent Legendrian knots K and K' such that W_K and W_K' are equivalent. On the other hand\, we will discuss an example of a Legendrian knot K that is characterized by its sy mplectic 4-manifold W_K. This is based on joint work with Roger Casals and John Etnyre.\nNo previous knowledge on contact geometry is assumed. We wi ll discuss all relevant notions in detail.\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Raede (Augsburg University) DTSTART:20210202T131500Z DTEND:20210202T144500Z DTSTAMP:20260404T094802Z UID:GoeTop/17 DESCRIPTION:Title: Macroscopic band width inequalities\nby Daniel Raede (Augsburg University) as part of Göttingen topology and geometry seminar\n\nAbstrac t: TBA\n LOCATION:https://stable.researchseminars.org/talk/GoeTop/17/ END:VEVENT END:VCALENDAR