Topic: 
Ultrafast heat transfer in nanoscale materials 
Date: 
27.05.19 
Time: 
16:15 
Place: 
H6 
Guest: 

University of Illinois 

Abstract: 
On the macroscopic lengths scales of conventional engineering systems, heat transfer by conduction is generally a slow process welldescribed by the heat diffusion equation. The characteristic timescale of diffusion scales with the square of length; therefore, at nanometer length scales, heat conduction can involve processes that occur on timescales of picoseconds, i.e., a few trillionth of a second. We use ultrafast pumpprobe optical techniques to directly study a variety of unconventional heat transfer mechanisms that are critical in nanoscale devices and nanoscale materials. Our studies encompass a diverse variety of systems (metallic nanoparticles for photothermal medical therapies, phase change materials for solidstate memory, and heatassisted magnetic recording) and physical mechanisms (the thermal conductance of interfaces between dissimilar materials, the nonequilibrium between thermal excitations of electrons, phonons, and magnons, and the crossterms in the transport of heat, charge, and spin). In this talk I will highlight three recent examples: i) ultrafast thermal transport in the surroundings of plasmonic nanostructures; ii) limitations on ultrafast heating of metallic multilayers imposed by electronphonon coupling; and iii) the generation of currents of magnetization by the spindependent Seebeck effect and extreme heat fluxes exceeding 100 GW m^{2}. 
Contact person: 
Topic: 
The WidomRowlinson model: metastability, mesoscopic and microscopic fluctuations for the critical droplet 
Date: 
24.05.19 
Time: 
16:15 
Place: 
V3204 
Guest: 
Elena Pulvirenti 
University of Bonn 

Abstract: 
In this talk I will discuss the WidomRowlinson model on a finite two dimensional torus subject to a stochastic dynamics in which particles are randomly created and annihilated inside the torus according to an infinite reservoir with a given chemical potential. We are interested in the metastable behaviour of the system at low temperature when the chemical potential is supercritical. In particular, we compute the asymptotics of the average time the system needs to condensate and we describe the shape of the critical droplet. Our results rely on a precise analysis of the microscopic and mesoscopic fluctuations of the surface of the critical droplet. This is a joint work in progress with F. den Hollander, S. Jansen, R. Kotecky. 
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Topic: 
On the relation between lowscale leptogenesis and dark matter 
Date: 
28.05.19 
Time: 
14:15 
Place: 
D6135 
Guest: 

Univ. Bern 

Abstract: 
There has been recent interest in leptogenesis induced by "light" righthanded neutrinos, with masses in the GeV range. Apart from accounting for the observed baryon asymmetry, this scenario may produce lepton asymmetries much larger than the baryon asymmetry. A possible consequence of the latter could be keVscale sterile neutrino dark matter production through the resonantly enhanced ShiFuller mechanism. Making use of a "complete" theoretical framework, which tracks both helicity states of the righthanded neutrinos as well as their kinetic nonequilibrium, and solving numerically a set of nonlinear evolution equations, we explore to what extent such a minimal scenario could represent a viable explanation for dark matter and baryogenesis. 
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Topic: 
Matrix product states and matrix product operators 
Date: 
13.06.19 
Time: 
14:15 
Place: 
D5153 
Guest: 
Murod Bahohavinov 
Bielefeld University 

Abstract: 

Contact person: 
Topic: 
Critical behaviour and characteristic polynomials of nonHermitian random matrices 
Date: 
23.05.19 
Time: 
16:15 
Place: 
D5153 
Guest: 

University of Sussex 

Abstract: 
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). 
Contact person: 
Topic: 
Planar orthogonal polynomials and boundary universality for random normal matrices 
Date: 
29.05.19 
Time: 
16:15 
Place: 
V3201 
Guest: 

The Royal Institute of Technology 

Abstract: 
We obtain an asymptotic expansion for the orthogonal polynomials with respect to exponentially varying weights. This formula is applied to yield error function universality for the interface at regular boundary points. This reports on joint work with A. Wennman. 
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