Oberseminare und sonstige Vorträge

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Anita Kollwitz

Romain Panis, Univ. Geneva: The long-range Phi^4 model on Z^d (Oberseminar Mathematische Stochastik)

Wednesday, 24.04.2024 16:00 im Raum SRZ 216

Mathematik und Informatik

We study the (discrete) Phi^4 model on Z^d with algebraically decaying long-range interactions. This model is the natural discrete analogue of the fractional continuous Phi^4 model. We first describe some general properties of the phase transition that the model undergoes. Then, we study the nature of the critical scaling limits of the model, proving in particular the (marginal) triviality of these limits in dimension 3 with well-chosen interactions.



Angelegt am Monday, 18.03.2024 14:55 von Anita Kollwitz
Geändert am Wednesday, 17.04.2024 09:44 von Anita Kollwitz
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Oberseminare und sonstige Vorträge
Stochastik
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Gabi Dierkes

Dr. Irma Pallarés Torres (Leuven): Characteristic classes and singular varieties. (Research Seminar on Geometry, Algebra and Topology: Moduli Spaces of Complex Curves)

Wednesday, 24.04.2024 16:15 im Raum M3

Mathematik und Informatik

Abstract: Characteristic classes of manifolds are usually cohomology classes associated to the tangent bundle of the manifold. Hirzebruch's theory unifies three important theories of characteristic classes of smooth manifolds: Chern classes, Todd classes and Thom-Hirzebruch L-classes. In 2010, Brasselet, Schürmann and Yokura extended Hirzebruch classes to singular varieties using natural transformations, and unified in a functorial sense the three theories of Chern classes, Todd classes and L-classes for singular varieties. In this talk, we will delve into the relationships between these classes.



Angelegt am Thursday, 18.04.2024 11:18 von Gabi Dierkes
Geändert am Thursday, 18.04.2024 11:18 von Gabi Dierkes
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Oberseminare und sonstige Vorträge
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Claudia Rüdiger

Alexis Aumonier (University of Cambridge): Stable cohomology of moduli of smooth hypersurfaces

Wednesday, 24.04.2024 16:30 im Raum M4

Mathematik und Informatik

Abstract: The space of all smooth hypersurfaces of a given degree in a complex projective variety is itself a variety. I will explain how to understand some of its cohomology using tools from homotopy theory: smooth hypersurfaces are given by holomorphic sections of line bundles subject to a differential condition, and these can be compared to continuous sections of appropriate jet bundles. This strategy usually goes under the name of "h-principle", and we will see an algebraic instance of that. I will also explain some consequences: a cohomological stability phenomenon, and a relation to classifying spaces of diffeomorphism groups of hypersurfaces.



Angelegt am Wednesday, 10.04.2024 11:00 von Claudia Rüdiger
Geändert am Wednesday, 10.04.2024 11:00 von Claudia Rüdiger
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Oberseminare und sonstige Vorträge
Sonstige Vorträge
Vorträge des SFB 1442
Veranstaltungen am Mathematischen Institut
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Elke Enning

Aaron Tikuisis (z.Z. Oxford): Central sequences and topological dynamics. Oberseminar C*-Algebren.

Tuesday, 23.04.2024 16:15 im Raum SRZ 216/217

Mathematik und Informatik

Central sequences play a fundamental role in operator algebras, from property Gamma and the MacDuff property for II_1 factors to characterizations of tensorial absorption for C*-algebras, for example. Given the deep link between operator algebras and dynamics, it is natural to look for dynamical analogues of central sequence properties. This turns out to be subtle. In joint work with Grigorios Kopsacheilis, Hung-Chang Liao, and Andrea Vaccaro, a central sequence property (uniform property Gamma) is shown to be equivalent to a topological dynamical property (the small boundary property). I will discuss a body of work related to these ideas.



Angelegt am Thursday, 04.04.2024 07:55 von Elke Enning
Geändert am Thursday, 11.04.2024 06:37 von Elke Enning
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Oberseminare und sonstige Vorträge
Vorträge des SFB 1442
Veranstaltungen am Mathematischen Institut
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Paulina Weischer

Jerónimo García-Mejía: Dehn functions of nilpotent groups

Thursday, 25.04.2024 11:00 im Raum SR4

Mathematik und Informatik

Since Gromov's celebrated polynomial growth theorem, the understanding of nilpotent groups has become a cornerstone of geometric group theory. An interesting aspect is the conjectural quasiisometry classification of nilpotent groups. One important quasiisometry invariant that plays a significant role in the pursuit of classifying these groups is the Dehn function, which quantifies the solvability of the world problem of a finitely presented group. Notably, Gersten, Holt, and Riley's work established that the Dehn function of a nilpotent group of class $c$ is bounded above by $n^{c+1}$. In this talk, I will explain recent results that allow us to compute Dehn functions for extensive families of nilpotent groups arising as central products. Consequently, we obtain a large collection of pairs of nilpotent groups with bilipschitz equivalent asymptotic cones but with different Dehn functions. This talk is based on joint work with Claudio Llosa Isenrich and Gabriel Pallier.



Angelegt am Tuesday, 16.04.2024 06:47 von Paulina Weischer
Geändert am Tuesday, 16.04.2024 06:47 von Paulina Weischer
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Oberseminare und sonstige Vorträge
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Anke Pietsch

Tee-Seminar: Hendrik Van Maldeghem (Universität Gent, Belgien): Generalised dualities and Segre varieties

Monday, 29.04.2024 14:15 im Raum SR1C

Mathematik und Informatik

Jacques Tits generalised the notion of a "polarity" in order to describe all embeddable polar spaces. We further extend it to the notion of "generalised duality". We use it to classify and describe all geometric hyperplanes of a Segre geometry, which is the direct product of two arbitrary projective spaces. This result, in turn, can be applied to Segre varieties over arbitrary fields and we obtain an explicit list of all geometric hyperplanes that are not induced by a projective hyperplane. Among them are so-called black hyperplanes, which are embedded long root geometries of type A, and we will mention some special features about those.



Angelegt am Thursday, 04.04.2024 10:22 von Anke Pietsch
Geändert am Thursday, 04.04.2024 10:30 von Anke Pietsch
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Oberseminare und sonstige Vorträge
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Sandra Huppert

Oberseminar Differentialgeometrie: Renan Assimos (Universität Hannover), Vortrag: tba

Monday, 29.04.2024 16:00 im Raum SRZ 214

Mathematik und Informatik



Angelegt am Thursday, 07.03.2024 10:42 von Sandra Huppert
Geändert am Thursday, 07.03.2024 10:42 von Sandra Huppert
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Oberseminare und sonstige Vorträge
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