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David Lopez-Cardozo

"Finite size scaling and the critical Casimir force : Ising magnets and binary fluids"
When Oct 22, 2015
from 02:00 PM to 04:25 PM
Where Amphi Schrodinger, site Monod, ENS de Lyon
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Jury:

Denis Bartolo,
Sergio Ciliberto,
David Dean (Université de Bordeaux),
Andrea Gambassi (SISSA),
Björgvin Hjörvarsson (Uppsala Universitet)
Peter Holdsworth.
 
Abstract:
 
Approaching a critical point, the divergence of the correlation length of fluctuations can be cut-off by a confinement of the system. This truncation fosters finite size effects with universal features in a class of continuous phase transitions.
We are particularly interested in the Ising universality class, regrouping transitions such as the ferromagnetic/paramagnetic transition for uniaxial magnetic systems, the liquid/gas transition and the demixing of binary mixtures. We will first present an introduction to critical phenomena, universality, finite-size scaling and Monte Carlo simulations of the Ising model, on which a major part of this work relies.
A finite size effect that has particularly drawn attention in the past decades is the critical Casimir force. On the one hand, theoretical and numerical works on the subject have almost systematically been performed in magnetic model systems, such as the Ising or XY models. On the other hand, experimental approaches were all realized in fluid systems, such as binary mixtures or helium IV close to the superfluid transition.
A motivation of this work was to bridge this gap by proposing, firstly, an experimental protocol for measuring the critical Casimir force in a magnetic layer and, secondly, a numerical approach in a Lennard-Jones binary mixture. The latter is of particular interest as it could lead the way to studying fluctuations of the Casimir force or out-of-equilibrium phenomena.