Studium | Forschung | Organisation | Personen | Universität | 
change language

Aktuelle Veranstaltungen

 

Kolloquium

Thema:

Soft X-ray Spectroscopy of Quantum Materials

Datum:

15.11.22

Uhrzeit:

14:15

Ort:

H6

Vortragender:

Prof. Kai Rossnagel

Universität Kiel

Inhalt:

Ansprechpartner:

A. Hütten

Kolloquium Mathematische Physik

Thema:

tba

Datum:

04.11.22

Uhrzeit:

16:15

Ort:

D5-153

Vortragender:

Lisa Hartung

Universität Mainz

Inhalt:

Ansprechpartner:

G. Akemann

Seminar Hochenergiephysik

Thema:

Mitigating the Hubbard Sign Problem. A Novel Application of Machine Learning

Datum:

07.11.22

Uhrzeit:

16:15

Ort:

D6-135

Vortragender:

Marcel Rodekamp

FZ Jülich

Inhalt:

Many fascinating systems suffer from a severe (complex action) sign problem preventing us from simulating them with Markov Chain Monte Carlo. One promising method to alleviate the sign problem is the transformation towards Lefschetz Thimbles. Unfortunately, this suffers from poor scaling originating in numerically integrating of flow equations and evaluation of an induced Jacobian. In this talk we present a Neural Network architecture based on complex-valued affine coupling layers. This network performs such a transformation efficiently, ultimately allowing simulation of systems with a severe sign problem. We test this method within the Hubbard Model at finite chemical potential, modelling strongly correlated electrons on a spatial lattice of ions.

Ansprechpartner:

O. Kaczmarek

Seminar Kondensierte Materie

Thema:

Assigning Temperatures to Eigenstates

Datum:

04.11.22

Uhrzeit:

14:15

Ort:

D5-153

Vortragender:

Masudul Haque

TU Dresden

Inhalt:

In formulating the statistical mechanics of isolated quantum systems, an inescapable issue is the definition of temperature, which is not a priori defined within closed-system quantum mechanics. We examine and compare different possible ways of assigning temperatures to energies, or equivalently, to eigenstates. The commonly used assignment of temperature is based on the canonical energy-temperature relationship, which depends only on energy eigenvalues and not on the structure of eigenstates. For eigenstates, we consider defining temperature by minimizing the distance between (full or reduced) eigenstate density matrices and canonical density matrices. We show that for full eigenstates, the minimizing temperature depends on the distance measure chosen, and matches the canonical temperature for the trace distance; however the two matrices are not close. With reduced density matrices, the minimizing temperature has fluctuations that scale with subsystem and system size but is apparently independent of distance measure, and in particular limits the two matrices become equivalent.

Ansprechpartner:

FOR2692/Jürgen Schnack

Seminar Mathematische Physik

Thema:

tba

Datum:

01.12.22

Uhrzeit:

16:00

Ort:

D5-153

Vortragender:

José Gracia Bondia

University of Zaragoza, Spain

Inhalt:

Ansprechpartner:

Gernot Akemann

Seminar Bielefeld-Melbourne Zufallsmatrizen

Thema:

Matrix integrals in a tensor setup

Datum:

12.10.22

Uhrzeit:

09:00

Ort:

ZOOM / Konferenzschaltung

Vortragender:

Benoit Collins

Tokyo

Inhalt:

We will describe the first part of a series of joint works with Luca Lionni and Razvan Gurau in which we generalize the study of HCIZ integrals to higher-order tensors. We obtain developments for the HCIZ integral and its logarithm that are new even in the original setup. Time allowing, we will discuss applications to free probability theory and quantum information theory.

Ansprechpartner:

Mario Kieburg



  • @ Uni Bielefeld
  • | Letzte Änderung: 30.06.2020
  •  Olaf Kaczmarek
  • | Kontakt
  • | Datenschutz
  • | Impressum
  • | Druckansicht PDF