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:20260422T115912Z UID:GoeTop/1 DESCRIPTION:Title: O n the homotopy type of the space of metrics of positive scalar curvature\nby Johannes Ebert (University of Münster) as part of Göttingen topol ogy and geometry seminar\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/GoeTop/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Georg Frenck (Karlsruhe Institute of Technology) DTSTART:20200519T123000Z DTEND:20200519T133000Z DTSTAMP:20260422T115912Z UID:GoeTop/3 DESCRIPTION:Title: H -space structures on spaces of metrics of positive scalar curvature\nb y Georg Frenck (Karlsruhe Institute of Technology) as part of Göttingen t opology and geometry seminar\n\n\nAbstract\nWe construct and study an $H$- space multiplication on $\\mathcal{R}^+(M)$ for simply connected Spin-mani folds $M$ which are Spin-nullcobordant. This will lead to a form of comput ation called "graphical calculus" which is the used to derive a rigidity c riterion for the action of the diffeomorphism group on $\\mathcal{R}^+(M)$ via pullback. We will also indicate\, how to get rid of the assumption of being simply connected and Spin.\n LOCATION:https://researchseminars.org/talk/GoeTop/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Saskia Roos (University of Potsdam) DTSTART:20200526T123000Z DTEND:20200526T133000Z DTSTAMP:20260422T115912Z UID:GoeTop/4 DESCRIPTION:Title: T he chiral anomaly of the free Fermion in functorial field theory\nby S askia Roos (University of Potsdam) as part of Göttingen topology and geom etry seminar\n\n\nAbstract\nWhen trying to cast the free fermion in the fr amework of functorial field theory\, its chiral anomaly manifests in the f act that it assigns the determinant of the Dirac operator to a top-dimensi onal closed spin manifold\, which is not a number as expected\, but an ele ment of a complex line. In functorial field theory language\, this means t hat 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 func tor that sends manifolds to infinite-dimensional Clifford algebras and bor disms to bimodules.\n LOCATION:https://researchseminars.org/talk/GoeTop/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Jinmin Wang (Shanghai Center for Mathematical Sciences) DTSTART:20200602T143000Z DTEND:20200602T153000Z DTSTAMP:20260422T115912Z UID:GoeTop/5 DESCRIPTION:Title: A pproximation of delocalized eta invariants by their finite analogues\n by Jinmin Wang (Shanghai Center for Mathematical Sciences) as part of Göt tingen topology and geometry seminar\n\n\nAbstract\nThe delocalized eta in variant for self-adjoint elliptic operators was introduced by Lott as a na tural extension of the classical eta invariant of Atiyah-Patodi-Singer. In this talk\, we will give several results on when the delocalized eta inva riant can be approximated by the ones associated with finite-sheeted cover ing spaces\, under a necessary assumption of conjugacy distinguishability. In the first part\, we will present a result using a K-theoretical approa ch of the delocalized eta invariant. In the second part\, we will give a q uantized description of conjugacy distinguishability. This is a joint work with Zhizhang Xie and Guoliang Yu.\n LOCATION:https://researchseminars.org/talk/GoeTop/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Benjamin Waßermann (Karlsruhe Institute of Technology) DTSTART:20200623T143000Z DTEND:20200623T153000Z DTSTAMP:20260422T115912Z UID:GoeTop/6 DESCRIPTION:Title: T he $L^2$-Cheeger Müller Theorem and its applications to hyperbolic lattic es\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 analytic an d the topological $L^2$-torsion of odd-dimensional manifolds. \n\nLet $M$ be a compact\, smooth\, odd-dimensional manifold-with-boundary satisfying $\\chi(M) = 0$ and let $\\rho \\colon \\pi_1(M) \\to \\GL(V)$ be a finite- dimensional unimodular representation of its fundamental group. Provided t hat the pair $(M\,\\rho)$ is $L^2$-acyclic and a technical determinant cla ss condition is satisfied\, two positive real numbers $T_{An}^{(2)}(M\,\\r ho)\,T_{Top}^{(2)}(M\,\\rho)$\, the analytic and topological $L^2$-torsion of $(M\,\\rho)$\, can be defined. \n\nWhile $T_{Top}^{(2)}(M\,\\rho)$ is constructed solely with the aid of any arbitrary CW-structure on $M$\, a R iemannian 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 recent resu lt\, which establishes the relationship between the two quantities and fro m which follows that they agree in many instances. \n\nIn the second part\ , we will consider odd-dimensional hyperbolic manifolds of finite volume ( in particular\, not necessarily compact spaces) and representations of the ambient Lie group. In this instance\, another recent result is presented which extends the definition of $T_{An}^{(2)}(M\,\\rho)$ and $T_{Top}^{(2) }(M\,\\rho)$ and shows the equality of the two quantities in this case.\n LOCATION:https://researchseminars.org/talk/GoeTop/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Paolo Antonini (SISSA Trieste) DTSTART:20200609T123000Z DTEND:20200609T133000Z DTSTAMP:20260422T115912Z UID:GoeTop/7 DESCRIPTION:Title: T he Baum–Connes conjecture localised at the unit element of a discrete gr oup\nby Paolo Antonini (SISSA Trieste) as part of Göttingen topology and geometry seminar\n\n\nAbstract\nLet Γ be a discrete group\; we constr uct a Baum–Connes map localised at the\nunit element of Γ. This is an a ssembly map in KK–theory with real coefficients\nleading to a form of th e Baum–Connes conjecture which is intermediate between\nthe Baum–Conne s conjecture and the Strong Novikov conjecture.\nThe localised assembly ma p has an interesting property: it is functorial with\nrespect to group mor phisms.\nWe explain the construction and we show that the relation with th e Novikov\nconjecture follows from a comparison at the level of KKR-theory of the classifying space for free and proper actions EΓ with the classif ying space for proper\nactions EΓ.\nBased on joint work with Sara Azzali and Georges Skandalis.\n LOCATION:https://researchseminars.org/talk/GoeTop/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Demetre Kazaras (Stony Brook University) DTSTART:20200616T143000Z DTEND:20200616T153000Z DTSTAMP:20260422T115912Z UID:GoeTop/8 DESCRIPTION:Title: S calar curvature\, mass\, and harmonic maps\nby Demetre Kazaras (Stony Brook University) as part of Göttingen topology and geometry seminar\n\n\ nAbstract\nFor a 3-dimensional Riemannian manifold there is a relationship between the level sets of a harmonic map and the manifold's scalar curvat ure\, expressed by a formula discovered by Daniel Stern. New proofs of cla ssical facts in the study of scalar curvature can be given with this formu la. We adopt this harmonic map perspective to give novel bounds for the ma ss of asymptotically flat initial data sets in terms of certain asymptotic ally linear functions. As a consequence\, we obtain a new proof of the spa ce-time Positive Mass Theorem in dimension 3. These results are joint work with Hugh Bray\, Sven Hirsch\, Marcus Khuri\, and Daniel Stern.\n LOCATION:https://researchseminars.org/talk/GoeTop/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Jian Wang (University of Augsburg) DTSTART:20200714T143000Z DTEND:20200714T153000Z DTSTAMP:20260422T115912Z UID:GoeTop/9 DESCRIPTION:Title: C ontractible 3-manifolds and Positive scalar curvature\nby Jian Wang (U niversity of Augsburg) as part of Göttingen topology and geometry seminar \n\n\nAbstract\nIt is unknown that a contractible 3-manifold has a complet e metric with positive scalar curvature. The topology of contractible 3-ma nifolds is much complicated. For example\, the Whitehead manifold is a con tractible 3-manifold but not homeomorphic to $\\mathbb{R}^3$. In this talk \, we will present the proof that it has no complete metric with positive scalar curvature. We will further explain that a complete contractible 3-m anifold with positive scalar curvature and trivial fundamental group at in finity is homeomorphic to $\\mathbb{R}^3$.\n LOCATION:https://researchseminars.org/talk/GoeTop/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Ulrich Bunke (University of Regensburg) DTSTART:20200804T123000Z DTEND:20200804T133000Z DTSTAMP:20260422T115912Z UID:GoeTop/10 DESCRIPTION:Title: Spectrum-valued $\\mathrm{KK}^G$\, Paschke duality and assembly maps\n by Ulrich Bunke (University of Regensburg) as part of Göttingen topology and geometry seminar\n\n\nAbstract\nI will explain a version of Paschke-du ality which connects the usual equivariant analytic $\\mathrm{K}$-homology theory with the equivariant $\\mathrm{K}$-homology theory derived from eq uivariant coarse $\\mathrm{K}$-homology. The Davis-Lück assembly map can be expressed through the coarse homology theory. Using Paschke duality we identify it with the classical version of the Baum-Connes assembly map vi a descent and Kasparov’s projection. All this will be phrased using a sp ectrum-valued $\\mathrm{KK}^G$-theory\, and we allow coefficients in $\\ma thrm{C}^\\ast$-categories with $G$-action.\n LOCATION:https://researchseminars.org/talk/GoeTop/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Tom Dove (University of Göttingen) DTSTART:20201110T131500Z DTEND:20201110T144500Z DTSTAMP:20260422T115912Z UID:GoeTop/11 DESCRIPTION:Title: Twisted Equivariant Tate K-Theory\nby Tom Dove (University of Götting en) as part of Göttingen topology and geometry seminar\n\n\nAbstract\nEqu ivariant Tate K-theory is an equivariant cohomology theory built on the K- theory of orbifold loop spaces. I’ll introduce the construction of this theory\, in particular the loop groupoid\, which serves as an equivariant analogue of the free loop space. After this I will describe the main purpo se of my masters thesis: constructing a twisted version of equivariant Tat e K-theory.\n LOCATION:https://researchseminars.org/talk/GoeTop/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Schick (University of Göttingen) DTSTART:20201117T131500Z DTEND:20201117T144500Z DTSTAMP:20260422T115912Z UID:GoeTop/12 DESCRIPTION:Title: Flexibility and Rigidity of Lipschitz Riemannian Geometry\nby Thomas S chick (University of Göttingen) as part of Göttingen topology and geomet ry seminar\n\n\nAbstract\nEvery smooth isometric embedding of the 2-sphere into\n$\\mathbb{R}^3$ the standard one (upto rotations\, translations\, a nd reflections).\n\nIn contrast to this classical rigidity result we have flexibility:\nThere are Lipschitz isometric embeddings of the 2-sphere in $\\mathbb{R}^3$ whose image\nhas arbitrarily small diameter.\n\nThe talk w ill present more of these surprising flexibility results for\nLipschitz ma ps 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 sm ooth map between a compact Riemannian manifold M and\nS^n with the standar d metric. If M is sufficiently curved (scalar\ncurvature is everywhere >= the scalar curvature of $S^n$)\, if the map is\nnon-expanding (Lipschitz c onstant <=1) and if it is far enough from a constant\nmap (has non-zero de gree) then f must be an isometry.\n\nWe will discuss the ideas of the proo f\, which involve the geometry of vector\nbundles\, and Gromov's question whether rigidity prevails or flexibility occurs\nif just have Lipschitz co ntinuity in the setup of the above theorem.\n LOCATION:https://researchseminars.org/talk/GoeTop/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Thorsten Hertl (University of Göttingen) DTSTART:20201124T131500Z DTEND:20201124T144500Z DTSTAMP:20260422T115912Z UID:GoeTop/13 DESCRIPTION:Title: Cubical Models for Positive Scalar Curvature\nby Thorsten Hertl (Unive rsity of Göttingen) as part of Göttingen topology and geometry seminar\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 methods com ing from index theory. \nDue to its concordance invariance\, we propose an other space to study which only \nencoded concordance information in its n ature.\nWe will then present an attempt to factorise the index difference over this space.\nThis project is part of my ongoing Ph.D. thesis and is w ork in progress.\n LOCATION:https://researchseminars.org/talk/GoeTop/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Markus Hausmann (University of Bonn) DTSTART:20201201T131500Z DTEND:20201201T144500Z DTSTAMP:20260422T115912Z UID:GoeTop/14 DESCRIPTION:Title: Complex bordism and the equivariant Quillen theorem\nby Markus Hausman n (University of Bonn) as part of Göttingen topology and geometry seminar \n\n\nAbstract\nIn 1969\, Quillen showed that the formal group law of comp lex bordism is the\nuniversal one\, and hence the complex bordism ring is isomorphic to the Lazard\nring. In my talk I will first recall this classi cal story and then discuss an\nequivariant version of Quillen’s theorem\ , over a fixed abelian group and in a\nglobal equivariant setting.\n LOCATION:https://researchseminars.org/talk/GoeTop/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Andreas Wagenblast (University of Göttingen) DTSTART:20201208T131500Z DTEND:20201208T144500Z DTSTAMP:20260422T115912Z UID:GoeTop/15 DESCRIPTION:Title: Topology of spaces of loops\nby Andreas Wagenblast (University of Göt tingen) as part of Göttingen topology and geometry seminar\n\n\nAbstract\ 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. This fact is no longer true for the pure untwisted rings/wickets). After that I wan t to explain the geometric method of Brendle and Hatcher\, explained in th eir 2010 paper titled *Configuration Spaces of Rings and Wickets* for comp uting some of the fundamental groups and demonstrate this on some examples . There is\, however\, a limitation of this procedure\, i.e. the method do es not imediately apply to *pure untwisted wickets*. In the last part of m y talk I will point out this problem and indicate a (hopefully possible) s olution to this\, which (if it works out) in the end will be some of my re sults of my master thesis.\n LOCATION:https://researchseminars.org/talk/GoeTop/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Marc Kegel (Humboldt University Berlin) DTSTART:20210126T131500Z DTEND:20210126T144500Z DTSTAMP:20260422T115912Z UID:GoeTop/16 DESCRIPTION:Title: Characterizing slopes for Legendrian knots\nby Marc Kegel (Humboldt Un iversity Berlin) as part of Göttingen topology and geometry seminar\n\n\n Abstract\nCharacterizing slopes for Legendrian knots:\nFrom a given Legend rian knot K in the standard contact 3-sphere\, we can construct a symplect ic 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 discus s an example of a Legendrian knot K that is characterized by its symplecti c 4-manifold W_K. This is based on joint work with Roger Casals and John E tnyre.\nNo previous knowledge on contact geometry is assumed. We will disc uss all relevant notions in detail.\n LOCATION:https://researchseminars.org/talk/GoeTop/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Raede (Augsburg University) DTSTART:20210202T131500Z DTEND:20210202T144500Z DTSTAMP:20260422T115912Z UID:GoeTop/17 DESCRIPTION:Title: Macroscopic band width inequalities\nby Daniel Raede (Augsburg Univers ity) as part of Göttingen topology and geometry seminar\n\nAbstract: TBA\ n LOCATION:https://researchseminars.org/talk/GoeTop/17/ END:VEVENT END:VCALENDAR