December 2024
Location: Mathematisches Institut, Raum 1.016 (Lipschitz-Saal), Endenicher Allee 60
Location: MPIM Lecture Hall
Abstract: Representations of affine Hecke algebras are of considerable interest since they essentially control the representation theory of p-adic groups. This talk discusses how these algebras can be studied using geometric methods. We will start by reviewing the groundbreaking work of Kazhdan-Lusztig who gave a geometric construction of affine Hecke algebras with equal parameters via equivariant K-theory and the work of Kato who extended this to the unequal parameter setting in type C. Building on these ideas, I will then explain a new construction that realises affine Hecke algebras with unequal parameters in all types.
Abstract: The next Tea Time will take place on the 6th of December from 4 to 6pm in the Lipschitzsaal. This time the topic is “(Re)claiming your space”. We want to discuss in which specific situations gender changes our experience as mathematicians and how to react when encountering such situations that affect us negatively. At the beginning of the event, we have invited Oana Padurariu and Paula Truöl (both MPIM) to share their thoughts in a discussion about their personal experiences and strategies. Afterwards we will discuss specific scenarios and possible reactions in smaller groups. Scenarios can be discussed in an abstract manner or even role-played. You can contribute scenarios that you would like to discuss either at the event or at the link below until the 4th of December. We will end the event with relaxed discussions over tea and cookies as usual. The event will be primarily in English but there will be a German group for the scenarios. We are looking forward to seeing you there! Link to contribute scenarios: https://forms.gle/S6uJRqN8jtTwSfgV9
Location: Lipschitzsaal.
Location: MPIM Lecture Hall
Location: Lipschitzsaal
Location: Max Planck Institut für Mathematik, MPIM Hörsaal (Vivatsgasse 7, 53111 Bonn)
Location: Institut für Angewandte Mathematik, Lipschitz-Saal (Raum 1.016), Endenicher Allee 60, 53115 Bonn
Location: Endenicher Allee 60, Lipschitz hall
Abstract: Finite-type Artin groups were first defined as generalizations of braid groups, and many of the combinatorial techniques used to study these groups were developed by generalizing classical tools for the braid groups. Since braid groups are also mapping class groups, it is reasonable to ask if some of the more geometric methods for studying mapping class groups could also be extended to finite-type Artin groups. In this talk, I will define generalizations of both the curve graph and the marking complex for finite-type Artin groups, discuss some of their similarities with the classical versions, and explain what we can learn from the actions of finite-type Artin groups on these spaces.
Abstract: A moldable job is a job that can be executed on an arbitrary number of processors, and its processing time depends on the number of processors allotted to it. A moldable job is monotone if its work doesn't decrease for an increasing number of allotted processors. This talk addresses the problem of scheduling monotone moldable jobs to minimize the makespan. For certain compact input encodings, a polynomial algorithm has a running time polynomial in n and log m, where n is the number of jobs and m is the number of machines. We explore how monotony can counteract the complexity arising from compact encodings and present tight bounds on the approximability of the problem with compact encoding: it is NP-hard to solve optimally, but admits a PTAS. The main focus is on efficient approximation algorithms, including a (3/2+ϵ)-approximate algorithm with a running time polynomial in log m and 1/ϵ, and linear in the number n of jobs. This is joint work with Kilian Grage, Felix Land, and Felix Ohnesorge.
Location: Seminarraum, 1st floor, Forschungsinstitut für Diskrete Mathematik/Arithmeum, Lennéstraße 2, 53113 Bonn
Location: Lipschitz Saal
Abstract: We consider the following boundary value problem on a compact Riemann surface split into two pieces by a collection of Jordan curves. Given an L^2 harmonic one-form on one of the pieces, we seek a harmonic one-form with the same boundary values and specified cohomology, which we call the "overfare" of the original form. When the Jordan curves are quasicircles, which are irregular curves arising in (for example) complex dynamics and Teichmüller theory, overfare is bounded. Furthermore, an associated scattering matrix is unitary. This has applications to approximation theory in complex analysis, Teichmüller theory, and conformal field theory. We give a non-technical overview of the analytic and geometric properties of overfare and related integral operators.
Note: Coffee, tea, and cookies will be served after the talk in Conference Room 2.025.
For details about the Oberseminar talks, please check the following link.
Program: We are looking forward to the talks of:
- Tobias Marschall (Institute for Medical Biometry and Bioinformatics, University of Düsseldorf): A human pangenome and methods for genome inference
- Jonas Arruda* (IRU Mathematics & Life Sciences, University of Bonn): Overcoming Selection Bias in Statistical Studies with Simulation-Based Inference
* Unfortunately, we have to postpone the visit of Amandine Véber to 2025. Instead, Jonas Arruda will present his work.
Location: Lipschitzsaal
Abstract: In his famous book Theory of Sound (18771878), Lord Rayleigh posed the following question: What shape of a drum membrane produces the lowest possible sound for a
fixed membrane area? The answer (the disc) was obtained by Lord Rayleigh using physical heuristics and rigorously proven later by Faber and Krahn in 1921. A contemporary analogue of this problem in Riemannian geometry is as follows: Given a compact surface without boundary and a natural number k, determine the supremum of the k-th eigenvalue of the Laplace-Beltrami operator (depending on a Riemannian metric) over the space of all Riemannian metrics with a fixed area. This challenging problem is remarkably rich and deeply connected to classical fields such as Differential and Algebraic Geometry, Geometric Analysis, PDEs, and Topology. In particular, the relationship between critical metrics for eigenvalues and minimal or harmonic maps has proven to be an especially powerful tool.
Location: Endenicher Allee 60, Lipschitz hall
Abstract: Gromov and Thurston constructed infinite families of manifolds that have metrics of pinched negative curvature but no metrics of constant negative curvature by taking cyclic branched covers of hyperbolic manifolds over codimension-two, totally geodesic submanifolds. We show that some of these branched covers satisfy Singer's L^2-Betti number vanishing conjecture using skew fields and special cube complex technology, partially answering a question raised by Gromov. Joint work with Boris Okun and Kevin Schreve.
January 2025
Location: Lipschitzsaal
Location: Endenicher Allee 60, Lipschitz hall
Location: Lipschitzsaal
Location: Endenicher Allee 60, Lipschitz hall
Location: Endenicher Allee 60, Lipschitz hall
Location: Endenicher Allee 60, Lipschitzsaal
The event is booked out, the reservation has been closed.
The annual symposium following the final meeting of the 2025 Abel Prize Committee will his year take place in Bonn.
Location: Lipschitzsaal
Location: Endenicher Allee 60, Lipschitz hall
February 2025
Location: Endenicher Allee 60, Lipschitz hall
Location: Seminar room, Arithmeum, Lennéstr. 2
March 2025
June 2025
Location: Lipschitz-Saal, Endenicher Allee 60, Bonn
Location: Endenicher Allee 60, Lipschitz hall