Thema: 
Critical transitions in Earth system dynamics 
Datum: 
24.01.22 
Uhrzeit: 
16:15 
Ort: 
cyberspace 
Vortragender: 

Technical University of Munich and Potsdam Institute for Climate Impact Research 

Inhalt: 
Both theory and evidence from paleoclimate proxy records econding the evolution of the climate system in the longterm past suggest that some components of the Earth system can respond abruptly to gradual changes in forcing. These transitions can be described in terms of bifurcations in nonlinear dynamical systems, which also hints at means to atnicipate them. After giving some basic elements of the underlying theory, we review some of the potentially mutlistable subsystems, focusssing on paleoclimate and observational data. These include the polar ice sheets, the Atlantic Meridional Overturning Circulation, as well as tropical rainforests and monsoon systems. We discuss different ways to predict their future evolution under anthropogenic forcing. 
Ansprechpartner: 
Thema: 
20220506Volker BachTBC 
Datum: 
06.05.22 
Uhrzeit: 
16:15 
Ort: 
ZOOM/Konferenzschaltung 
Vortragender: 

Technische Universität Braunschweig 

Inhalt: 
TBC 
Ansprechpartner: 
Thema: 
Gravitational Waves from Strong FirstOrder Phase Transitions 
Datum: 
15.02.22 
Uhrzeit: 
14:15 
Ort: 
Online, via ZOOM 
Vortragender: 

University of Helsinki 

Inhalt: 
In many extensions of the Standard Model, the electroweak transition is first order  in some cases, strongly so. The ensuing phase transition would result in collisions of bubbles of the new Higgs phase. These collisions, and the associated interactions of sound waves in the plasma, are substantial sources of gravitational waves. For a phase transition at or around the electroweak scale, these gravitational waves may be detectable by future missions such as LISA. They can indirectly provide a probe of particle physics beyond the Standard Model, complementary to future colliders. However, concrete predictions of the resulting gravitational waves will require good understanding both of the particle physics models themselves, as well as the nonequilibrium physics of the transition. In other words, we need accurate studies of the phase diagrams in the underlying particle physics theories, as well as good predictions of the expected gravitational wave signal from simulations. These feed into one another, forming a socalled 'pipeline'. The stronger the phase transition, the better the chance of being detected (or constrained) by future missions like LISA. However, strong transitions are also the most poorly understood. In this talk I will discuss some recent results from different points along the 'pipeline', with a focus on the consequences for strong firstorder phase transitions. 
Ansprechpartner: 
Thema: 
Toroidale Momente in anisotropen Spinsystemen 
Datum: 
21.01.22 
Uhrzeit: 
14:15 
Ort: 
Hybrid  Zoom/D5153 
Vortragender: 
Daniel Pister 
Universität Bielefeld 

Inhalt: 

Ansprechpartner: 
Thema: 
On NonHermitian BetaEnsembles 
Datum: 
14.10.21 
Uhrzeit: 
16:00 
Ort: 
D5153 
Vortragender: 

Universität Bielefeld 

Inhalt: 
Loggases 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 Loggases in two dimensions, i.e. in the nonHermitian 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 nearestneighbour spacing distribution of large matrices. In the second part of the talk we introduce the study of symmetry classes in nonHermitian RMT. We conjecture that the classes of complex symmetric and complex quaternion matrices can be effectively described by Loggases in two dimensions with noninteger inverse temperatures. 
Ansprechpartner: 
Thema: 
Eigenvectors of Truncated Unitary Ensembles 
Datum: 
26.01.22 
Uhrzeit: 
09:00 
Ort: 
ZOOM / Konferenzschaltung 
Vortragender: 

IST Austria 

Inhalt: 
Left and right eigenvectors of nonHermitian random matrices can be chosen so as to form a biorthogonal family. One of the most relevant statistics about them is the "matrix of overlaps", introduced in the late 90's by Chalker & Mehlig and studied since in different models, using a variety of techniques. I will present some recent progress on the study of overlaps between eigenvectors in the Truncated Unitary Ensembles (truncations of Haardistributed unitary matrices) and related models of random matrices. 
Ansprechpartner: 