Thermodynamic equilibrium in the expanding universe
arXiv:gr-qc/9905015 · doi:10.1023/A:1026741228100
Abstract
We show that a relativistic gas may be at ``global'' equilibrium in the expanding universe for any equation of state , provided that the gas particles move under the influence of a self-interacting, effective one-particle force in between elastic binary collisions. In the force-free limit we recover the equilibrium conditions for ultrarelativistic matter which imply the existence of a conformal timelike Killing vector.
10 pages, Latex, to appear in GRG