2 JOINT ICTP/SISSA STATISTICAL PHYSICS SEMINARS

[Quantitative Life Sciences]

JOINT ICTP/SISSA STATISTICAL PHYSICS SEMINAR

Friday, 28 November - 11:00 hrs

SISSA, Santorio Building,  Cinema Room' 1st floor

François LANDES (ICTP)

"Viscoelastic Interfaces Driven in Disordered Media  & Applications to 
Friction"


Abstract:
Many complex systems respond to a continuous input of energy by an 
accumulation of stress over time, interrupted by sudden energy releases 
called avalanches. Recently, it has been pointed out that several basic 
features of avalanche dynamics are induced at the microscopic level by 
relaxation processes, which are neglected by most models. We have 
studied a minimal modification of a well-known model of avalanche 
dynamics, in which we take into account the presence of "relaxation 
processes". Precisely, we study a viscoelastic interface driven in a 
disordered medium.

In mean-field, we prove that our model interface has a periodic behavior 
(with a new, emerging time scale), with avalanche events that span the 
whole system. We compute semi-analytically the friction force acting on 
this surface, and find that it is compatible with classical friction 
experiments.

In finite dimensions (2D), the mean-field system-sized events become 
local, and numerical simulations give qualitative and quantitative 
results in good agreement with several important features of real 
earthquakes.

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JOINT ICTP/SISSA STATISTICAL PHYSICS SEMINAR

Tuesday, 2 December - 11:00 hrs

SISSA, Santorio Building, Cinema Room, 1st floor


Gabriele Martelloni (SISSA)


"Quantum Quench from a thermal tensor state: two stationary states, NESS 
and GGE"


Abstract:

We consider a non-interacting Fermi gas in d dimensions, both in the 
non- relativistic and relativistic case. The system of size Ld is 
initially prepared into two halves L and R, each of them thermalized at 
two different temperatures, TL and TR respectively. At time t = 0 the 
two halves are put in contact and the entire system is left to evolve 
unitarily. We show that, in the thermodynamic limit, the time evolution 
of the particle and energy densities is perfectly described by a 
semiclassical approach which permits to analytically evaluate the 
correspondent stationary currents. In particular, in the case of 
non-relativistic fermions, we find a low-temperature behavior for the 
particle and energy currents which is independent from the 
dimensionality d of the system, being proportional to the difference TL2 
− TR2 . Moreover we consider the same problem of two halves, thermalized 
at different temperatures, for two 1d XX chains using the Quench Action 
Method (QAM). We show that two different stationary regimes are reached 
at long times, depending on the interplay between the observation time 
scale T and the total length L of the system. We show the emergence of a 
non-equilibrium steady state (NESS) supporting an energy current for 
observation time T much smaller than the system size L. We then identify 
a longer time-scale for which thermalization occurs in a Generalized 
Gibbs Ensemble (GGE).





-- 
Quantitative Life Sciences
The Abdus Salam International Centre for Theoretical Physics (ICTP)
Trieste,  Italy
Tel. +39-040-2240623
e-mail: qls at ictp.it