EPFL Topology Seminar 2018/19

Tuesdays at 10:15

CM 1 113


Date Title Speaker

in CM 012

The loop homology algebra of discrete torsion Yasuhiko Asao

University of Tokyo

09.10.2018 Topological Hochschild Homology and Fixed Point Invariants Jonathan Campbell

Vanderbilt University

16.10.2018 K-Theory and Polytopes Jonathan Campbell

Vanderbilt University

23.10.2018 Toward the equivariant stable parametrized h-cobordism theorem Mona Merling

University of Pennsylvania

30.10.2018 Tools for understanding topological coHochschild homology Anna Marie Bohmann

Vanderbilt University

06.11.2018 Thom spectra and Calabi-Yau algebras Inbar Klang


Periodic orbits and topological restriction homology
Cary Malkiewich

Binghamton University

20.11.2018 Arpon Raksit

Stanford University

27.11.2018 Calista Bernard

Stanford University

18.12.2018 Martina Rovelli

Johns Hopkins University

05.03.2019 Sune Precht Reeh

Universitat Autònoma de Barcelona

(See also the program of the topology seminar in 2011/12,  2010/11,  2009/102008/09,  2007/08, 2006/07, and 2005/06.)


Yasuhiko Asao – The loop homology algebra of discrete torsion

Let $M$ be a closed oriented manifold with a finite group action by $G$.
We denote its Borel construction by $M_{G}$. As an extension of string
topology due to Chas-Sullivan, Lupercio-Uribe-Xicot$\’{e}$ncatl
constructed a graded commutative associative product (loop product) on $
H_{*}(LM_{G})$, which plays a significant role in the “orbifold string
topology” . They also showed that the constructed loop product is an
orbifold invariant. In this talk, we describe the orbifold loop product
by determining its “twisting” out of  the ordinary loop product in term
of the group cohomology of $G$, when the action is homotopically trivial.
Through this description, the orbifold loop homology algebra can be
seen as R. Kauffmann’s “algebra of discrete torsion”, which is a group
quotient object of Frobenius algebra. As a cororally, we see that the
orbifold loop product is a non-trivial orbifold invariant.

Jonathan Campbell –  Topological Hochschild Homology and Fixed Point Invariants

Fixed point theorists have an array of invariants for determining if a self-map is homotopic to one without fixed points – most are elaborations of the classical Lefschetz invariant. In this talk, I’ll discuss these invariants and show that they arise very naturally from topological Hochschild homology. Furthermore, the invariants are in the image on components of the cyclotomic trace from K-theory to THH. This suggests higher K-theory and THH as homes for more refined fixed-point data. In order to make the talk accessible I’ll define the objects involved – a knowledge of the stable homotopy category is the only prerequisite. This is joint work with Kate Ponto.

Jonathan Campbell – K-Theory and Polytopes

In this talk I’ll describe joint work in progress with Inna Zakharevich to understand the relationship between algebraic K-theory and the scissors congruence problem. I’ll define both algebraic K-theory and the scissors congruence problem, and then describe various ways of using the former to attack the latter. And possible ways that the latter can shed light on the former.

Mona Merling –  Toward the equivariant stable parametrized h-cobordism theorem

Waldhausen’s introduction of A-theory of spaces revolutionized the early study of pseudo-isotopy theory. Waldhausen proved that the A-theory of a manifold splits as its suspension spectrum and a factor Wh(M) whose first delooping is the space of stable h-cobordisms, and its second delooping is the space of stable pseudo-isotopies. I will describe a joint project with C. Malkiewich aimed at telling the equivariant story if one starts with a manifold M with group action by a finite group G.

Anna Marie Bohmann –  Tools for understanding topological coHochschild homology

Hochschild homology is a classical invariant of algebras.  A “topological” version, called THH, has important connections to algebraic K-theory, Waldhausen’s A-theory, and free loop spaces.  For coalgebras, there is a dual invariant called “coHochschild homology” and Hess and Shipley have recently defined a topological version called “coTHH,” which also has connections to K-theory, A-theory and free loops spaces.  In this talk, I’ll talk about coTHH (and THH) are defined and then discuss work with Gerhardt, Hogenhaven, Shipley and Ziegenhagen in which we develop some computational tools for approaching coTHH.

Inbar Klang –  Thom spectra and Calabi-Yau algebras

I’ll briefly introduce topological field theories, along with some examples of 2-dimensional ones. I’ll discuss how 2-dimensional TFTs are related to Calabi-Yau algebras, which are algebras that satisfy a certain dualizability condition. Then I will talk about joint work with Ralph Cohen, in which we defined and studied a spectrum-level generalization of the Calabi-Yau condition, as well as its relation to field theories and to symplectic geometry.

Cary Malkiewich – Periodic orbits and topological restriction homology

I will talk about a project to import trace methods, usually reserved for algebraic K-theory computations, into the study of periodic orbits of continuous dynamical systems (and vice-versa). Our main result so far is that a certain fixed-point invariant built using equivariant spectra can be “unwound” into a more classical invariant that detects periodic orbits. As a simple consequence, periodic-point problems (i.e. finding a homotopy of a continuous map that removes its n-periodic orbits) can be reduced to equivariant fixed-point problems. This answers a conjecture of Klein and Williams, and allows us to interpret their invariant as a class in topological restriction homology (TR), coinciding with a class defined earlier in the thesis of Iwashita and separately by Luck. This is joint work with Kate Ponto.

Arpon Raksit –  TBA


Calista Bernard –  TBA


Martina Rovelli –  TBA


Sune Precht Reeh –  TBA