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Fluctuations relations of equilibrium states with broken symmetry

David Lacoste (PCT, ESPCI)
When Jun 15, 2015
from 11:00 to 12:00
Where Centre Blaise Pascal
Attendees David Lacoste
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Fluctuation relations are symmetry relations satisfied by probability distributions of thermodynamic quantities, valid arbitrarily far from equilibrium. Such relations provide a direct way to measure the degree by which  time-reversal symmetry is broken in the fluctuations of non-equilibrium systems. One may wonder whether similar relations exist 
for more general broken symmetries even in equilibrium systems. In this presentation, we will show that indeed whenever a symmetry is broken explicitly by an external field in an 
equilibrium system, the probability distribution of the order parameter obeys a fluctuation relation, which is valid for any finite system [1]. In the thermodynamic limit, such relations have implications for the occurrence of spontaneous symmetry breaking. Finally, we will discuss some application of these results to measure free energies from equilibrium fluctuations.
[1] Isometric fluctuation relations for equilibrium states with broken symmetry,
 D. Lacoste and P. Gaspard, Phys. Rev. Lett. 113, 240602 (2014).

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