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Out of Equilibrium Dynamics in Soft and Condensed Matter (6761)

March 03, 2015 – March 05, 2015

Location: Buenos Aires, Argentina

Organizers:
Gustavo Lozano, CONICET
Frederic von Wijland, University Paris, Dider
Tomas Grigera, University of La Plata
Leticia Cugliandolo, University Pierre et Marie Curie, Paris

Overview:
Standard statistical mechanics and thermodynamics are usually devoted to the theory of macroscopic systems in thermal equilibrium. In many experimental realizations, actually some of the more interesting ones at present, the situation is, however, very different. The systems are in contact with equilibrated environments but, for one reason or another, they do not manage to equilibrate with them. The systems evolve in time in an out of equilibrium manner.

The list of systems evolving out of equilibrium is very long. The reasons for not reaching equilibrium with the environment are also varied. The most common cases are those in which the time needed to equilibrate the sample falls beyond the experimental timewindow like in the context of domain growth, phase separation and classical and quantum
glassy systems. Another important cause for lack of equilibration is the action of external forces that drive the samples out of equilibrium. In this context we can mention for instance, transport of heat and electrical currents through samples or rheological properties of glass forming liquids and glassy materials. The driven dynamics of granular and active matter is another example of this kind. The constituents of active matter, be them particles, lines or other, absorb energy from their environment or internal fuel tanks and use it to carry out motion. In this new type of soft condensed matter energy is partially transformed into mechanical work and partially dissipated in the form of heat. The units interact directly or through disturbances propagated in the medium. Some realizations are bacterial suspensions, the cytoskeleton in living cells, or even swarms of different animals. In other driven systems, such as sheared fluids, vibrated granular matter and driven vortex lattices, energy input occurs on the boundaries of the sample. Instead, in active matter energy input is located on the internal units and is homogeneously distributed in the sample. Moreover, the effect of the motors can be dictated by the state of the particle and/or its immediate neighborhood and it is not necessarily fixed by an external field.

In the study of non equilibrium dynamics one usually selects the relevant variables, say the particle positions, spins, currents, etc, and treats the coupling to all other variables as the coupling to an external bath, e.g., phonons, photons, etc. which are assumed to be in equilibrium. In mesoscopic cases one is mostly interested in local couplings to currentcarrying leads, i.e. fermionic baths. In cold atomic gases the light fields confining the gas can also lead to dissipative processes. In many cases of interest, the coupling to the environment can be modeled a la Langevin, this is, by a stochastic differential equation that encodes in a phenomenological way, dissipation of heat to the bath and the effect of thermal fluctuations into the system via stochastic random forces.

The goal of the workshop is to open a space for discussion of the latest results on
statistical mechanics and evolution of out-of-equilibrium systems, with special emphasis in
condensed and soft matter. This will be the first workshop of this kind to be organized in
Argentina.



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