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Talks and seminars, possibly part of a conference or series.

Hopfological algebra, revisited

Posted in
Speaker: 
Gustavo Jasso
Affiliation: 
Universität zu Köln
Date: 
Fri, 17/07/2026 - 14:15 - 15:15
Location: 
MPIM Lecture Hall

This talk is based on joint work with Omar Gómez (Bielefeld) and Marius Nielsen (NTNU). Hopfological algebra is a variant of classical homological algebra introduced by Khovanov and Qi, motivated by potential applications in the categorification of quantum invariants of 3-manifolds. In this talk, I will explain an infinity-categorical approach to the theory that leads, in particular, to refined foundations as well as to "hopfological analogues" of classical invariants such as Hochschild (co)homology.

tba

Posted in
Speaker: 
Lola Thompson
Affiliation: 
Utrecht University
Date: 
Thu, 16/07/2026 - 16:30 - 17:30
Location: 
MPIM Seminar Room
Parent event: 
Number theory lunch seminar

tba

Posted in
Speaker: 
Lola Thompson
Affiliation: 
Utrecht University
Date: 
Thu, 16/07/2026 - 16:30 - 17:30
Location: 
MPIM Seminar Room
Parent event: 
Number theory lunch seminar

tba

Posted in
Speaker: 
N.N.
Date: 
Wed, 15/07/2026 - 16:00 - 17:00
Location: 
MPIM Lecture Hall

Spectral gap of random hyperbolic surfaces

Posted in
Speaker: 
Ivan Yakovlev
Affiliation: 
MPIM
Date: 
Tue, 14/07/2026 - 16:30 - 17:30
Location: 
MPIM Seminar Room

I will report on recent results of Hide-Magee, Anantharaman-Monk, Hide-Macera-Thomas proving that random hyperbolic surfaces of large genus have near optimal spectral gap. I will mention results from random graph theory that inspired much of the work on surfaces, and I will try to highlight some ideas from the works mentioned above.

 

tba

Posted in
Speaker: 
Igor Shparlinski
Affiliation: 
University of New South Wales
Date: 
Wed, 26/08/2026 - 14:30 - 15:30
Location: 
MPIM Lecture Hall
Parent event: 
Number theory lunch seminar

tba

Posted in
Speaker: 
William Banks
Affiliation: 
University of Missouri
Date: 
Wed, 19/08/2026 - 14:30 - 15:30
Location: 
MPIM Lecture Hall
Parent event: 
Number theory lunch seminar

tba

Posted in
Speaker: 
Antonella Perucca
Affiliation: 
University of Luxembourg
Date: 
Wed, 12/08/2026 - 14:30 - 15:30
Location: 
MPIM Lecture Hall
Parent event: 
Number theory lunch seminar

tba

Posted in
Speaker: 
Félicien Comtat
Affiliation: 
Universität Bonn
Date: 
Wed, 05/08/2026 - 14:30 - 15:30
Location: 
MPIM Lecture Hall
Parent event: 
Number theory lunch seminar

tba

Posted in
Speaker: 
Daniel Johnston
Affiliation: 
MPIM
Date: 
Wed, 29/07/2026 - 14:30 - 15:30
Location: 
MPIM Lecture Hall
Parent event: 
Number theory lunch seminar

tba

Posted in
Speaker: 
Simon Myerson
Affiliation: 
Chalmers University of Technology
Date: 
Wed, 22/07/2026 - 14:30 - 15:30
Location: 
MPIM Lecture Hall
Parent event: 
Number theory lunch seminar

C*-rigidity: a bridge between coarse geometry and C*-algebras

Posted in
Speaker: 
Federico Vigolo
Affiliation: 
Universität Göttingen
Date: 
Thu, 16/07/2026 - 16:30 - 17:30
Location: 
MPIM Lecture Hall

With every proper metric space are associated C*-algebras of special geometric importance (Roe algebras), originally defined for index-theoretic considerations. It is a simple observation that metric spaces that are coarsely equivalent give rise to isomorphic C*-algebras. Much more surprisingly, the converse also holds: a C*-rigidity Theorem shows that spaces with isomorphic Roe algebras must be coarsely equivalent.

Universal hyperbolic graphs and spaces and their isometry groups

Posted in
Speaker: 
Katrin Tent
Affiliation: 
University of Münster
Date: 
Thu, 16/07/2026 - 13:30 - 14:30
Location: 
MPIM Lecture Hall

I will present a construction of a universal homogeneous hyperbolic metric space, i.e. a metric space in which every finite hyperbolic space with rational distances can be isometrically embedded, in analogy to the Urysohn space. The isometry group of this space is a totally disconnected polish group and I will discuss simplicity and primitivity of the group and its action.

 

The arithmetic of Eisenstein series

Posted in
Speaker: 
Mads Bjerge Christensen
Affiliation: 
MPIM
Date: 
Tue, 14/07/2026 - 14:00 - 15:00
Location: 
MPIM Lecture Hall
Parent event: 
PLeaSANT

In a first course on modular forms, one encounters the Eisenstein series $E_k$ of even weight $k>2$. More generally, Eisenstein series arise in real analytic families parametrized by a complex parameter s, and holomorphic Eisenstein series like $E_k$ are particular special values of $s$. 

Deformations and A-infinity structures of Khovanov arc algebras

Posted in
Speaker: 
Severin Barmeier
Affiliation: 
Universität Köln
Date: 
Wed, 08/07/2026 - 14:15 - 15:15
Location: 
MPIM Lecture Hall

4-dimensional rational homology balls with cyclic fundamental group

Posted in
Speaker: 
Oleksandr Kharchenko
Affiliation: 
MPIM
Date: 
Fri, 17/07/2026 - 10:15 - 11:45
Location: 
MPIM Lecture Hall

KP integrability of Topological Recursion

Posted in
Speaker: 
Alexander Alexandrov
Affiliation: 
IBS/z. Z. MPIM
Date: 
Thu, 16/07/2026 - 15:00 - 16:00
Location: 
MPIM Lecture Hall
Parent event: 
MPI-Oberseminar

Topological recursion is a powerful tool in mathematical physics with pplications to various problems in enumerative geometry, including intersection theory on moduli spaces and Hurwitz numbers. In this talk, I will discuss the KP integrability of topological recursion, which arises naturally in the context of the x-y swap relation. I will explain how this KP integrability can be described via certain integral transforms, leading to Kontsevich-type matrix models.
 

Stacky approach and p-adic coefficients

Posted in
Speaker: 
Junhui Qin
Affiliation: 
Université de Strasbourg
Date: 
Tue, 14/07/2026 - 15:05 - 17:00
Location: 
MPIM Lecture Hall

A stacky approach to a cohomology theory is often useful for distilling its core properties, for instance in establishing a six-functor formalism and studying its coefficients. In this talk, using the theory of Gelfand stacks, we will study stacky approaches to the theory of p-adic coefficients, including rigid cohomology, overconvergent isocrystals, and arithmetic D-modules, and present some applications. 

 

Integral Chow motives of derived equivalent K3 surfaces

Posted in
Speaker: 
Evgeny Shinder
Affiliation: 
Sheffield
Date: 
Thu, 16/07/2026 - 10:30 - 11:30
Location: 
MPIM Lecture Hall

We prove that if X, Y are derived equivalent complex K3 surfaces, then the integral Chow motives are typically not isomorphic, but are always stably isomorphic. This unfies the result of Huybrechts for isomorphism of rational Chow motives with the result of Mukai for the stable equivalence of integral Hodge structures. Under some mild assumptions, the same result holds for K3 surfaces over nonclosed fields of characteristic zero. For the proofs we rely on known results about zero-cycles on K3 surfaces and set up the machinery of Tate-stable equivalence for integral Chow motives.

Quantum Ergodicity: from geodesic flow to Weyl's law

Posted in
Speaker: 
Eva-Maria Hekkelman
Affiliation: 
MPIM
Date: 
Tue, 07/07/2026 - 16:30 - 17:30
Location: 
MPIM Seminar Room

On compact Riemannian manifolds, a fascinating connection has been found
between geodesic flow and the eigenfunctions of the Laplace operator. If
the geodesic flow is ergodic, the eigenfunctions corresponding to large
eigenvalues will spread 'evenly' over the manifold. I will explain how
to make this precise, and in particular how the latter can be seen as a
stronger version of Weyl's law. This result from the '80s by Shnirelman,
Zelditch and Colin de Verdière was the start of the field that is now

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