# Aktuelle Veranstaltungen

## Kolloquium

Thema:

### Strong Coupling Approach to the QCD Phase Diagram

Datum:

23.05.22

Uhrzeit:

16:15

Ort:

H6

Vortragender:

PD Dr. Wolfgang Unger

Universität Bielefeld

Inhalt:

Quantum Chromodynamics (QCD) is the fundamental theory of the strong interactions, which confine the quarks and gluons into hadrons. At high temperatures similar to those in the early universe, a new state of QCD matter - the quark gluon plasma - exists. However, it is an open question what features the phase diagram has at non-zero baryon densities, and in particular whether there exists a critical point. Since QCD is non-perturbative in this regime, lattice QCD is the method of choice to unravel the phase structure at non-zero temperatures and densities from first principles via Monte Carlo simulations. However, due to the numerical “sign problem”, no direct simulations at non-zero baryon density can be performed. An alternative method to address lattice QCD at finite density is via the strong coupling expansion, which gives rise to Quantum Monte Carlo simulations in a world-line representation. I will summarize the results that have been obtained with this approach.

Ansprechpartner:

Dekan

## Kolloquium Mathematische Physik

Thema:

### tba

Datum:

03.06.22

Uhrzeit:

16:15

Ort:

V4-119

Vortragender:

Elena Vedmedenko

University of Hamburg

Inhalt:

Ansprechpartner:

M. Baake

Thema:

Datum:

30.06.22

Uhrzeit:

14:15

Ort:

D6-135

Vortragender:

Simona Procacci

Universität Bern

Inhalt:

Ansprechpartner:

D. Bödeker

## Seminar Kondensierte Materie

Thema:

### 14.00 tba

Datum:

03.06.22

Uhrzeit:

14:00

Ort:

ZOOM / Konferenzschaltung

Vortragender:

Jakub Mrozek

University of Oxford

Inhalt:

Ansprechpartner:

Jürgen Schnack

## Seminar Mathematische Physik

Thema:

### Many-particles diffusing with resetting: study of the large-deviation properties of the flux distribution

Datum:

05.05.22

Uhrzeit:

16:00

Ort:

D5-153

Vortragender:

Costantino Di Bello

Inhalt:

In this paper we studied a model of noninteracting particles moving on a line following a common dynamics. In particular we considered either a diffusive motion with Poissonian resetting, and a run-and-tumble motion with Poissonian resetting. We were interested in studying the distribution of the random variable $Q_t$ defined as the flux of particles through origin up to time $t$. We used the notation $P(Q,t)$ to identify the probability $\mathbb{P}\{Q_t=Q\}$. We considered particles initially located on the negative half line with a fixed density $\rho$. In fully analogy with disordered systems, we studied both the annealed and the quenched case for initial conditions. In the former case we found that, independently from the specific dynamics, $P_\mathrm{an}(Q,t)$ has a Poissonian shape; while in the latter case, for what concerns the diffusive dynamics with resetting, the large deviation form of the quenched distribution reads $P_\mathrm{qu}(Q,t)\sim \exp\left[-r^2t^2 \Psi_\mathrm{diff}\left(\dfrac{Q}{\rho t}\right)\right]$ with the large deviation function $\Psi_\mathrm{diff}(x)$ exhibiting a discontinuity in the third derivative, hence aiming, despite the simplicity of the model, at the exhistence of a dynamical phase transition. The quenched distribution for the run-and-tumble dynamics, instead, does not exhibit any kind of phase transition. Importance sampling Monte Carlo simulations were performed to prove the analytical results. References: Current fluctuations in noninteracting run-and-tumble particles in one dimension Tirthankar Banerjee, Satya N. Majumdar, Alberto Rosso, and Grégory Schehr, Phys. Rev. E 101, 052101 https://doi.org/10.1103/PhysRevE.101.052101 Current Fluctuations in One Dimensional Diffusive Systems with a Step Initial Density Profile B. Derrida and A. Gerschenfeld, J. Stat. Phys. 137, 978 (2009) https://doi.org/10.1007/s10955-009-9830-1

Ansprechpartner:

Gernot Akemann

## Seminar Bielefeld-Melbourne Zufallsmatrizen

Thema:

### Exponential Functional of the Matrix Brownian Motion, Dufresne Identity and Quantum Scattering

Datum:

25.05.22

Uhrzeit:

09:00

Ort:

ZOOM / Konferenzschaltung

Vortragender:

Aurélien Grabsch

LPTMC, Sorbonne Université

Inhalt:

Exponential functionals of the Brownian motion appear in many different contexts (classical diffusion in random media, quantum scattering, finance,...). I will discuss a recent generalization to the case of matrix Brownian motion. This problem has a natural motivation within the study of quantum scattering on a disordered wire with several conducting channels. I will show that the Wigner-Smith time delay matrix, a fundamental matrix in quantum scattering encoding several characteristic time scales, can be represented as an exponential functional of the matrix BM. I will discuss the relation between this problem of quantum physics and the Dufresne identity, which gives the stationary distribution of such exponential functionals of the BM. Ref: Aurélien Grabsch and Christophe Texier, Wigner-Smith matrix, exponential functional of the matrix Brownian motion and matrix Dufresne identity, J. Phys. A: Math. Theor. 53, 425003 (2020)

Ansprechpartner:

Anas Rahman

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