Termine

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Alexander Domke

Rob Sullivan: Sharply k-homogeneous actions on Fraïssé structures.

Thursday, 11.12.2025 11:00 im Raum SR1D

Mathematik und Informatik

Given an action of a group G on a relational Fraïssé structure M, we call this action sharply k-homogeneous if, for each isomorphism f : A -> B of substructures of M of size k, there is exactly one element of G whose action extends f. This generalises the well-known notion of a sharply k-transitive action on a set, and was previously investigated by Cameron, Macpherson and Cherlin. I will discuss recent results with J. de la Nuez González which show that a wide variety of Fraïssé structures admit sharply k-homogeneous actions for k ? 3 by finitely generated virtually free groups. Our results also specialise to the case of sets, giving the first examples of finitely presented non-split infinite groups with sharply 2-transitive/sharply 3-transitive actions.



Angelegt am 04.12.2025 von Alexander Domke
Geändert am 04.12.2025 von Alexander Domke
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Oberseminare und sonstige Vorträge
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Claudia Lückert

Wilhelm Killing Kolloquium: Prof. Dr. Mikaela Iacobelli (ETH Zürich): Challenges and Breakthroughs in the Mathematics of Plasmas

Thursday, 11.12.2025 14:15 im Raum M4

Mathematik und Informatik

This colloquium will explore some fundamental issues in the mathematics of plasmas, focusing on the stability and instability of solutions to Vlasov-type equations, which are crucial for describing the behavior of charged particles in a plasma. A general introduction to kinetic theory is given, making the subject accessible to a wide audience of mathematicians. Key mathematical concepts such as well-posedness, stability, and the behavior of solutions in singular limits are discussed. In addition, a new class of Wasserstein-type distances is introduced, offering new perspectives on the stability of kinetic equations.



Angelegt am 01.08.2025 von Claudia Lückert
Geändert am 21.11.2025 von Claudia Lückert
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Kolloquium Wilhelm Killing
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Claudia Giesbert

Oberseminar Stochastik: Dr. Mathias Sonnleitner (Universität Münster/Universität Bielefeld): Shedding light on the volume of high-dimensional Schatten balls

Wednesday, 10.12.2025 16:00 im Raum SRZ 216/217

Mathematik und Informatik

A natural generalization of the Lebesgue sequence space to the non-commutative setting of n by n-matrices is to take the p-norm of the singular values, the Schatten p-norm. Thus, in case of p equal to one we obtain the nuclear/trace norm, in case of p equal to two the Hilbert-Schmidt/Frobenius norm and in case of p equal to infinity the spectral norm. In this talk, we will be interested in the volume of Schatten p-balls, that is, unit balls with respect to Schatten p-norms, as their dimension tends to infinity. In contrast to the commutative analog, the finite-dimensional Lebesgue sequence space for which the volume of the unit ball is known since Dirichlet, exact results are only available for p equal to two and to infinity. Asymptotics for general p have been established starting in the 80's with two very recent contributions in the last month. We give insight on underlying connections to the theory of random matrices, logarithmic potentials and statistical mechanics. In particular, we highlight a large deviation principle due to Leblé and Serfaty from which we obtain finer asymptotics for the volume of Schatten $p$-balls in the self-adjoint case. Perhaps interestingly, both the differential entropy and its noncommutative analog - the free entropy - of the corresponding equilibrium measure appear.



Angelegt am 08.12.2025 von Claudia Giesbert
Geändert am 09.12.2025 von Claudia Giesbert
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Angewandte Mathematik Münster
Oberseminare und sonstige Vorträge
Stochastik
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Anke Pietsch

Tea Seminar: Prof. Markus Stroppel (Universität Stuttgart): Groups with many automorphisms

Tuesday, 09.12.2025 14:15 im Raum SR4

Mathematik und Informatik

For a topological group G, let Aut(G) be the group of all automorphisms, and let w(G) be the number of orbits of Aut(G) on G. I will report about results characterizing classes of groups G with suitable (topological or algebraic) assumptions on G, combined with bounds on w(G). In particular, there are strong results in the following cases: * G is locally compact and connected, with w(G) less than the cardinality of the continuum * G is compact, and w(G) is finite * G is finite, and w(G) < 5



Angelegt am 04.12.2025 von Anke Pietsch
Geändert am 04.12.2025 von Anke Pietsch
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Oberseminare und sonstige Vorträge
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Anke Pietsch

Prof. Dr. Markus Stroppel (Universität Stuttgart): Lectures on locally compact groups

Monday, 15.12.2025 14:15 im Raum SR 1D

Mathematik und Informatik

Markus Stroppel will give a lecture series on advanced topics in locally compact groups. The lectures take place on Monday at 14:15 in room SR 1D They will start on Monday, November 17. The planned topics are: * the scale function and tidy subgroups * automorphism groups of trees



Angelegt am 12.11.2025 von Anke Pietsch
Geändert am 12.11.2025 von Anke Pietsch
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Sonstige Vorträge
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Claudia Rüdiger

Prof. Dr. Achim Krause (Universität Oslo): H_infinity structures and delta rings

Monday, 15.12.2025 14:15 im Raum MB4

Mathematik und Informatik

Abstract: The bottom homotopy group of a flat commutative algebra over the sphere spectrum inherits a delta-ring structure from the Tate-valued Frobenius of Nikolaus-Scholze, which plays a big role in the relationship between trace methods and prismatic cohomology. It is an interesting question how much of the E_infty ring structure is remembered by this delta-ring structure. In this talk, we present a modest step towards understanding this, by proving that there is a one-to-one correspondence between H_infinity ring structures on flat S-modules and delta-ring structures on their pi_0.



Angelegt am 08.12.2025 von Claudia Rüdiger
Geändert am 08.12.2025 von Claudia Rüdiger
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Oberseminare und sonstige Vorträge
Vorträge des SFB 1442
Veranstaltungen am Mathematischen Institut
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Sandra Huppert

Oberseminar Differentialgeometrie: Siarhei Finski (Universität Paris), Vortrag: Weighted Bergman Kernels and Kähler Geometry

Monday, 15.12.2025 16:15 im Raum SRZ 216

Mathematik und Informatik

Abstract: Tian's classical theorem shows that, for a polarized complex projective manifold, the Bergman kernel grows asymptotically like a monic polynomial of degree equal to the dimension. I will present a weighted extension of this result that includes, for instance, equivariant and divisor-adapted Bergman kernels. In contrast to the classical case, the leading coefficient now reflects the speed of a geodesic ray in Mabuchi geometry associated with the weight. In the equivariant case, this speed coincides with the Hamiltonian of the induced circle action, while in the divisor case, it arises via a resolution of the Monge-Ampère equation on the deformation to the normal cone. Finally, I will discuss how this equidistribution result connects to the theory of canonical metrics, and in particular, its implications for the Wess-Zumino-Witten equation.



Angelegt am 11.08.2025 von Sandra Huppert
Geändert am 03.11.2025 von Sandra Huppert
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Oberseminare und sonstige Vorträge