Laboratoire Matière et Systèmes Complexes

September 14th 2020.

The seminar will take place exceptionally in the amphitheatre Pierre Gilles de Gennes. Level -1

The number of people is limited. Please send an email to Michael Berhanu to attend. There will be also a live diffusion with zoom. Contact Michael Berhanu to attend the video seminar.

Breaking of energy equipartition and spatial correlations in out-of-equilibrium systems

Eric Bertin, CNRS Senior Scientist

Laboratoire Interdisciplinaire de Physique (LIPhy), Grenoble

Abstract : Energy equipartition is a cornerstone of equilibrium statistical physics. For instance, the average kinetic energy per degree of freedom of a molecule is the same for translational and rotational motions. For (harmonic) interaction energies, equipartition of energy applies to extended modes like phonons, and not to the degrees of freedom of individual particles. Out of equilibrium, energy equipartition is in general broken, which may lead to enhanced spatial correlations. The formulation in terms of extended modes offers a natural framework to describe these phenomena. As an illustration, two driven systems of experimental relevance will be considered, an epithelial cell monolayer and an AFM cantilever heated by a laser beam. In the cell monolayer, where individual cell motility is correlated over long time scales, equipartition of energy over normal modes is strongly broken, and velocity correlations are present over distances of ten or more cell sizes.