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Accueil du site > Publications > Publications 2006 > Virial theorem and dynamical evolution of self-gravitating Brownian particles in an unbounded domain : I. Overdamped models

Virial theorem and dynamical evolution of self-gravitating Brownian particles in an unbounded domain : I. Overdamped models

Pierre-Henri Chavanis and Clément Sire

par Clément Sire - 11 avril 2006

We derive the Virial theorem appropriate to the generalized Smoluchowski-Poisson (GSP) system describing self-gravitating Brownian particles in an overdamped limit. We extend previous works by considering the case of an unbounded domain and an arbitrary equation of state. We use the Virial theorem to study the diffusion (evaporation) of an isothermal Brownian gas above the critical temperature T_{c} in dimension d=2 and show how the effective diffusion coefficient and the Einstein relation are modified by self-gravity. We also study the collapse at T=T_{c} and show that the central density increases logarithmically with time instead of exponentially in a bounded domain. Finally, for d>2, we show that the evaporation of the system is essentially a pure diffusion slightly slowed-down by self-gravity. We also study the linear dynamical stability of stationary solutions of the GSP system representing isolated clusters of particles and investigate the influence of the equation of state and of the dimension of space on the dynamical stability of the system.

http://xxx.lanl.gov/abs/cond-mat/0504718v2