Issue
EPL
Volume 84, Number 2, October 2008
Article Number 24002
Number of page(s) 5
Section Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics
DOI http://dx.doi.org/10.1209/0295-5075/84/24002
Published online 06 October 2008
EPL, 84 (2008) 24002
DOI: 10.1209/0295-5075/84/24002

Breakdown of the fluctuation-dissipation relations in granular gases

J. J. Brey1, M. I. García de Soria1, 2 and P. Maynar1, 3

1   Física Teórica, Universidad de Sevilla - Apartado de Correos 1065, E-41080 Sevilla, Spain, EU
2   LPTMS (CNRS UMR 8626), Université Paris-Sud - Orsay Cedex, F-91405 France, EU
3   Laboratoire de Physisque Théorique (CNRS UMR 8627), Bâtiment 210, Université Paris-Sud Orsay Cedex, F-91405 France, EU

brey@us.es

received 13 June 2008; accepted in final form 3 September 2008; published October 2008
published online 6 October 2008

Abstract
A numerical molecular dynamics experiment measuring the two-time correlation function of the transversal velocity field in the homogeneous cooling state of a granular gas modeled as an ensemble of inelastic hard particles is reported. By measuring the decay rate and the amplitude of the correlations, the accuracy of the Landau-Langevin equation of fluctuating hydrodynamics is checked. The results indicate that although a Langevin approach can be valid, the fluctuation-dissipation relation must be modified, since the viscosity parameter appearing in it differs from the usual hydrodynamic shear viscosity.

PACS
45.70.-n - Granular systems.
51.10.+y - Kinetic and transport theory of gases.

© EPLA 2008