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Colloquium

Topic:

Intelligente Energieversorgungsnetze

Date:

08.11.21

Time:

16:15

Place:

H4

Guest:

Prof. Jens Haubrock

FH Bielefeld

Abstract:

Contact person:

W. Pfeiffer

Colloquium Mathematical Physics

Topic:

Random matrices, spin glasses, and machine learning

Date:

23.07.21

Time:

16:15

Place:

ZOOM/Konferenzschaltung

Guest:

Jon Keating

Oxford University

Abstract:

I will describe some problems relating to machine learning and their connections to random matrix theory and spin glasses. These connections give a mathematical framework for understanding in qualitative terms the effectiveness of certain algorithms that are important in machine learning, but developing them into precise models remains a major challenge. I will reflect on the different roles played by models in computer science and physics, focussing on those involving random matrices.

Contact person:

G. Akemann

Seminar High Energy Physics

Topic:

Machine Learning for Thermodynamic Observables in Lattice Field Theories

Date:

06.07.21

Time:

14:15

Place:

Online, via ZOOM

Guest:

Lena Funcke

Perimeter Institute, Ontario, Canada

Abstract:

In this talk, I will discuss how applying machine learning techniques to lattice field theory is a promising route for solving problems where Markov Chain Monte Carlo (MCMC) methods are problematic. More specifically, I will show that deep generative models can be used to estimate thermodynamic observables like the free energy, which contrasts with existing MCMC-based methods that are limited to only estimate free energy differences. I will demonstrate the effectiveness of the proposed method for two-dimensional $\phi^4$ theory and compare it to MCMC-based methods in detailed numerical experiments.

Contact person:

G. Endrödi

Seminar Condensed Matter

Topic:

14:30 Untersuchung von frustrierten Spin-1/2-Systemen mit Hilfe von quantum-three-coloring am Beispiel des Kuboktaeders

Date:

14.10.21

Time:

14:30

Place:

Hybrid - Zoom/D5-153

Guest:

Florian Brökemeier

Universität Bielefeld

Abstract:

Contact person:

Jürgen Schnack

Seminar Mathematical Physics

Topic:

On Non-Hermitian Beta-Ensembles

Date:

14.10.21

Time:

16:00

Place:

D5-153

Guest:

Patricia Päßler

Universität Bielefeld

Abstract:

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.

Contact person:

Gernot Akemann

Seminar Bielefeld-Melbourne Random Matrices

Topic:

Central Limit Theorems to Stable and Invariant Random Matrices

Date:

20.10.21

Time:

09:00

Place:

ZOOM / Konferenzschaltung

Guest:

Mario Kieburg

Melbourne University

Abstract:

Heavy-tailed random matrices have surprising and novel effects that can be hardly seen with the classical ensembles. For instance, in recent years it was shown that heavy-tailed Wigner matrices can exhibit localised eigenvector statistics for the eigenvalues in the tail while everything stays the same as we know it for the bulk statistics of a GUE. This effect, some intriguing as well as real world applications, and some own numerical experiments have motivated us to study invariant heavy-tailed random matrices. One of the questions we have addressed has been about central limit theorems at fixed matrix dimensions and invariant random matrices that are stable when adding independent copies of the random matrix under consideration. I will report on our new findings and will sketch the main ideas of their proofs in the present talk. These projects have been carried out in collaboration with Jiyuan Zhang and Adam Monteleone.

Contact person:

Mario Kieburg



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