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Aktuelle Veranstaltungen

 

Kolloquium

Thema:

Critical transitions in Earth system dynamics

Datum:

24.01.22

Uhrzeit:

16:15

Ort:

cyberspace

Vortragender:

Dr. Niklas Boers

Technical University of Munich and Potsdam Institute for Climate Impact Research

Inhalt:

Both theory and evidence from paleoclimate proxy records econding the evolution of the climate system in the long-term past suggest that some components of the Earth system can respond abruptly to gradual changes in forcing. These transitions can be described in terms of bifurcations in nonlinear dynamical systems, which also hints at means to atnicipate them. After giving some basic elements of the underlying theory, we review some of the potentially mutlistable subsystems, focusssing on paleoclimate and observational data. These include the polar ice sheets, the Atlantic Meridional Overturning Circulation, as well as tropical rainforests and monsoon systems. We discuss different ways to predict their future evolution under anthropogenic forcing.

Ansprechpartner:

W. Pfeiffer

Kolloquium Mathematische Physik

Thema:

20220506-Volker Bach-TBC

Datum:

06.05.22

Uhrzeit:

16:15

Ort:

ZOOM/Konferenzschaltung

Vortragender:

Volker Bach

Technische Universität Braunschweig

Inhalt:

TBC

Ansprechpartner:

M. Baake

Seminar Hochenergiephysik

Thema:

Quantum-to-Classical Transition of Adiabatic and Entropy Perturbations in the Presence of an Axion-like Particle

Datum:

20.01.22

Uhrzeit:

14:15

Ort:

D6-135 + via Zoom

Vortragender:

Jondalar Kuß

Universität Bielefeld

Inhalt:

In my master´s thesis at Göttingen University I studied the effect that an axion-like particle being present during inflation as a light scalar field could have on the primordial perturbations, using the formalism of squeezed states. The axionic field becomes highly squeezed during inflation and remains so after reheating. Initially, it merely produces isocurvature perturbations, curvature is only sourced when the Hubble parameter becomes comparable to the axion mass.

Ansprechpartner:

D. Bödeker

Seminar Kondensierte Materie

Thema:

tba

Datum:

20.01.22

Uhrzeit:

14:15

Ort:

Hybrid - Zoom/D5-153

Vortragender:

Paul Angelike

Universität Bielefeld

Inhalt:

Ansprechpartner:

Peter Reimann

Seminar Mathematische Physik

Thema:

On Non-Hermitian Beta-Ensembles

Datum:

14.10.21

Uhrzeit:

16:00

Ort:

D5-153

Vortragender:

Patricia Päßler

Universität Bielefeld

Inhalt:

Log-gases with inverse temperature beta are systems with many applications in physics, for example in the theory of superconductors or the fractional quantum Hall effect. For some specific values of beta a correspondence to random matrix theory (RMT) is well established. The advantage of this connection is the usage of the RMT methods in the study of those systems. The goal of this talk is the discussion of Log-gases in two dimensions, i.e. in the non-Hermitian case, for more general values of the inverse temperature. Therefore, we study in the first part a model of normal 2 × 2 matrices with beta in [0,2] and discuss whether we find a surmise for the nearest-neighbour spacing distribution of large matrices. In the second part of the talk we introduce the study of symmetry classes in non-Hermitian RMT. We conjecture that the classes of complex symmetric and complex quaternion matrices can be effectively described by Log-gases in two dimensions with non-integer inverse temperatures.

Ansprechpartner:

Gernot Akemann

Seminar Bielefeld-Melbourne Zufallsmatrizen

Thema:

The Wasserstein distance to the Circular Law

Datum:

19.01.22

Uhrzeit:

09:00

Ort:

ZOOM / Konferenzschaltung

Vortragender:

Jonas Jalowy

Westfälische Wilhelms-Universität Münster

Inhalt:

In this talk we investigate the Wasserstein distance between the empirical spectral distribution of non-Hermitian random matrices and the Circular Law. For general entry distributions, I present a nearly optimal rate of convergence in 1-Wasserstein distance of order n^{-1/2+\epsilon} and show that the optimal rate n^{-1/2} is attained by Ginibre matrices. This reveals that the expected transport cost of complex eigenvalues to the uniform measure on the unit disk decays faster compared to that of i.i.d. points, which is known to include a logarithmic factor. We shall also discuss the results from a point of view of random geometry, which will be accompanied by illustrative simulations.

Ansprechpartner:

Gernot Akemann



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  •  Olaf Kaczmarek
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