Thema: 
Extreme nonlinear optics and strongfield physics in solids 
Datum: 
06.04.20 
Uhrzeit: 
16:15 
Ort: 
H6 
Vortragender: 

Univ. of Kyoto 

Inhalt: 

Ansprechpartner: 
Thema: 
Numerics for resonances of Schottky surfaces 
Datum: 
10.01.20 
Uhrzeit: 
16:15 
Ort: 
V3201 
Vortragender: 

Universität Bremen 

Inhalt: 
Resonances of Riemannian manifolds are of great importance in many areas of mathematics and physics. Even though many fascinating results about these spectral entities have already been found, an enormous amount of their properties, also some very elementary ones, is still undiscovered. A few years ago, by means of numerical experiments, Borthwick noticed for some classes of Schottky surfaces (certain hyperbolic surfaces of infinite area) that their sets of resonances exhibit unexcepted and nice patterns, which are not yet fully understood. After a survey of some parts of this field, we will discuss an alternative numerical method, combining tools from dynamics, zeta functions, transfer operators and thermodynamic formalism, functional analysis and approximation theory. This is joint work with Oscar Bandtlow, Torben Schick and Alexander Weiße. 
Ansprechpartner: 
Thema: 
Chiral charge dynamics in Abelian gauge theories at finite temperature 
Datum: 
18.02.20 
Uhrzeit: 
15:15 
Ort: 
D6135 
Vortragender: 

EPFL Lausanne 

Inhalt: 
The chiral anomaly present in the standard model can have important phenomenological consequences, especially in cosmology and heavyions physics. In this talk, I will focus on the contribution from the Abelian gauge fields. Despite an absence of topologically distinct sectors, they have a surprisingly rich vacuum dynamics, partly because of the chiral anomaly. I will present results obtained from realtime classical lattice simulations of a U(1) gauge field in the presence of a chiral chemical potential. They account for short distance fluctuations, contrary to effective descriptions such as MagnetoHydrodynamics (MHD). I will discuss various phenomena, like inverse magnetic cascade, which occur in this system. In particular, in presence of a background magnetic field, the chemical potential exponentially decays. The associated chiral decay rate is related to the diffusion of the Abelian ChernSimons number in a magnetic background, in the absence of chemical potential. The rate obtained from the simulations is an order of magnitude larger than the one predicted by MHD. If this result is shown to be robust under corrections such as Hard Thermal Loops, it will call for a revision of the implications of fermion number and chiral number nonconservation in Abelian theory at finite temperature. 
Ansprechpartner: 
Thema: 
BetheAnsatz für Fußgänger 
Datum: 
24.04.20 
Uhrzeit: 
14:15 
Ort: 
D5153 
Vortragender: 
Andreas Klümper 
Universität Wuppertal 

Inhalt: 

Ansprechpartner: 
Thema: 
Critical behaviour and characteristic polynomials of nonHermitian random matrices 
Datum: 
23.05.19 
Uhrzeit: 
16:15 
Ort: 
D5153 
Vortragender: 

University of Sussex 

Inhalt: 
I will discuss some recent developments regarding the normal matrix model. In particular my interest will be in certain critical models where the limiting support of the eigenvalues can radically change its topology by slightly adjusting an external parameter. I will discuss how aspects of the model can be explicitly mapped to the study of expectations of characteristic polynomials of nonHermitian random matrices (e.g. Ginibre or truncated unitary). Many of these averages are related to Painlevé transcendents, and by exploiting this, a precise and nontrivial asymptotic expansion of partition functions can be calculated in the critical models. This is joint work with Alfredo Deaño (University of Kent). 
Ansprechpartner: 
Thema: 
Dimensional reduction for elliptic SPDE's: integrable structures and large deviations 
Datum: 
18.12.19 
Uhrzeit: 
16:15 
Ort: 
V3201 
Vortragender: 

University of Warwick 

Inhalt: 
I will review the phenomenon of dimensional reduction for elliptic stochastic PDE's in two and three dimensions due to hidden supersymmetry discovered by Parisi and Sourlas. I will use dimensional reduction to establish a link between matrixvalued elliptic SPDE's and determinantal point processes. I will show that the large deviations principle can be established for a class of equations without any reference to supersymmetry. The talk is based on joint work with Roger Tribe and David Elworthy 
Ansprechpartner: 