Topic: 
Strong Coupling Approach to the QCD Phase Diagram 
Date: 
23.05.22 
Time: 
16:15 
Place: 
H6 
Guest: 

Universität Bielefeld 

Abstract: 
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 nonzero baryon densities, and in particular whether there exists a critical point. Since QCD is nonperturbative in this regime, lattice QCD is the method of choice to unravel the phase structure at nonzero temperatures and densities from first principles via Monte Carlo simulations. However, due to the numerical “sign problem”, no direct simulations at nonzero 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 worldline representation. I will summarize the results that have been obtained with this approach. 
Contact person: 
Topic: 
tba 
Date: 
03.06.22 
Time: 
16:15 
Place: 
V4119 
Guest: 

University of Hamburg 

Abstract: 

Contact person: 
Topic: 
tba 
Date: 
30.06.22 
Time: 
14:15 
Place: 
D6135 
Guest: 

Universität Bern 

Abstract: 

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Topic: 
15:00 Indicators of manybody quantum chaos 
Date: 
19.05.22 
Time: 
15:00 
Place: 
ZOOM / Konferenzschaltung 
Guest: 

Yeshiva University, New York 

Abstract: 
Quantum chaos, specially when caused by interactions between particles, has experienced a remarkable resurgence in the last decade due to its close relationship with a broad spectrum of problems at the forefront of theoretical and experimental physics. Quantum chaos ensures thermalization, hinders localization, and leads to the fast scrambling of quantum information in manybody quantum systems. In this lecture, I will compare different indicators of quantum chaos associated with the spectrum and eigenstates of manybody quantum systems. 
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Topic: 
Manyparticles diffusing with resetting: study of the largedeviation properties of the flux distribution 
Date: 
05.05.22 
Time: 
16:00 
Place: 
D5153 
Guest: 
Costantino Di Bello 
Abstract: 
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 runandtumble 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 runandtumble 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 runandtumble 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/s1095500998301 
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Topic: 
Exponential Functional of the Matrix Brownian Motion, Dufresne Identity and Quantum Scattering 
Date: 
25.05.22 
Time: 
09:00 
Place: 
ZOOM / Konferenzschaltung 
Guest: 

LPTMC, Sorbonne Université 

Abstract: 
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 WignerSmith 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, WignerSmith matrix, exponential functional of the matrix Brownian motion and matrix Dufresne identity, J. Phys. A: Math. Theor. 53, 425003 (2020) 
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