November 2024
Location: HIM lecture hall (Poppelsdorfer Allee 45, Bonn)
Location: Max Planck Institute - Lecture Hall
Abstract:
Let X be a very general hypersurface of dimension 3 and degree d at least 6. Griffiths and Harris conjectured in 1985 that the degree of every curve on X is divisible by d. Substantial progress on this conjecture was made by Kollár in 1991 via degeneration arguments. However, the conjecture of Griffiths and Harris remained open in any degree d. In this talk, I will explain how to prove this conjecture (and its higher-dimensional analogues) for infinitely many degrees d.
Location: MPIM Seminar Room
Location: MPIM Lecture Hall
Location: MPIM Lecture Hall
Location: MPIM Lecture Hall
Location: Endenicher Allee 60, SR 1.008
Abstract:
A 2-graded group is a pair: a group G and its index two subgroup H (even elements). Its representation is a complex representation of H with an action of the other coset G\H (odd elements) in another way that needs to be chosen. Different choices lead to 4 different theories that I will review in the first half. A 2-graded 2-group is a 2-group GG such that the fundamental group π1(GG) is 2-graded. Now different choices of how GG could act on a 2-vector space lead to 8 different theories, that I will review in the second half.
The talk is based on my recent works with James Taylor (Oxford) and Matthew B. Young (Utah State).
Location: Endenicher Allee 60, Room 0.006
Abstract:
The study of time harmonic electromagnetic waves at a flat interface of dispersive (i.e. frequency dependent) media leads to a non-self-adjoint Maxwell operator pencil. A classical application is to surface plasmon polaritons at the interface of a dielectric and a metal. We assume that the interface is flat and the media in the two half spaces are spatially homogenous and unbounded. The dependence of the permittivity on the spectral parameter (frequency) is generally nonlinear. The whole spectrum consists of eigenvalues and the essential spectrum, but the various standard types of essential spectra do not coincide in all cases. The functional setting is such that the operator domain is not a subset of the range which brings about a difficulty in defining the discrete spectrum. The spectral analysis is complete in one and two dimensions; in collaboration with Malcolm Brown (Cardiff), Michael Plum (Karlsruhe), and Ian Wood (Canterbury). In the case of cubically (Kerr) nonlinear materials monochromatic solutions do not exist. In the one dimensional case we find polychromatic solutions in the form of an infinite series of odd harmonics with the frequency of the leading order term being a complex eigenvalue of the linear problem. This work is in collaboration with Max Hanisch (Halle) and Runan He (Madrid).
Location: MPIM Lecture Hall
Location: Lipschitzsaal
Location: MPIM Lecture Hall
Location: MPIM Lecture Hall
Location: MPIM Lecture Hall
Location: Institut für Angewandte Mathematik, Lipschitz-Saal, Endenicher Allee 60, 53115 Bonn
Location: MPIM Lecture Hall
Location: University of Bonn, N0.003 (new building)
Location: MPIM Seminar Room
Location: MPIM Lecture Hall
Location: Endenicher Allee 60, Lipschitz hall
Location: MPIM Seminar Room
Location: Endenicher Allee 60, Raum 0.003
Abstract: A folkloric conjecture of Scott states the following: If G is the free group of rank N and f is any automorphism of G, then the subgroup of elements fixed by f has rank at most N. This was first shown by Bestvina and Handel in 1992, for which they develop the theory of train-track maps in free groups. In this talk, we will give a new proof from the viewpoint of L^2-homology. Our method readily applies to other groups, including surface groups. We also establish some properties of the Linnell ring of G which may be of independent interest.
Location: MPIM Lecture Hall
Location: Max Planck Insitut - Hörsaal
Abstract: we prove the Kuznetsov components of a series of hypersurface in projective space reconstruct the hypersurfaces. Our method allow us to work for hypersurfaces in weighted projective space, and obtain the reconstruction theorem of veronese double cone, which is a long-time open case. I will show how to construct the infinitesimal variation of Hodge structure from certain Kuznetsov components. Using classical generic Torelli theorem, this implies the Kuznetsov components reconstruct the algebraic variety generically. Joint with J. Rennemo and S.Z. Zhang.
Location: MPIM Seminar Room
Location: MPIM Lecture Hall
Location: MPIM Lecture Hall
Location: MPIM Lecture Hall
Location: MPIM Lecture Hall
Location: MPIM Lecture Hall
Location: Endenicher Allee 60, Lipschitzssaal
Do you identify with a specific gender? Why though? On November 29, Solveïg (none or hen/hens pronouns) will give us an insight into non-binary perspectives on gender and sex in about 45 minutes. No prior knowledge is required, Solveïg will speak in German and summarize key points in English. Afterwards there will be the opportunity to discuss the topic in smaller groups and spend time with other interested people over tea and cookies. We start at 15 c.t. with the talk in the Lipschitzsaal. If you can‘t make it to the talk, don‘t worry about it and join us at 4 pm for discussion, tea and cookies.
See you then!
Your LGBTQ+ Department
December 2024
Location: Lipschitzsaal
Location: Endenicher Allee 60, Lipschitz hall
Location: Endenicher Allee 60, Lipschitz Lecture Hall
Abstract: We present a general shape optimization framework based on the method of mappings in the Lipschitz topology. We propose and numerically analyse steepest descent and Newton-like minimisation algorithms for the numerical solution of the respective shape optimization problems. Our work is built upon previous work of the authors in (Deckelnick, Herbert, and Hinze, ESAIM: COCV 28 (2022)), where a Lipschitz framework for star-shaped domains is proposed. To illustrate our approach we present a selection of PDE constrained shape optimization problems and compare our findings to results from so far classical Hilbert space methods and recent p-approximations. This is joint work with Klaus Deckelnick from Magdeburg and Philip Herbert from Sussex.
Location: MPIM Lecture Hall
Details: MPIM Conference Page
Location: Lipschitzsaal
Location: Endenicher Allee 60, Lipschitz hall
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: Lipschitzsaal
Location: Endenicher Allee 60, Lipschitz hall
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