  Thermodynamics of the near extremal black p-branes can be described by
collective motions of gravitationally interacting branes. This proposal is
called the p-soup model. In this paper, we check this proposal in the case of
black brane system which is asymptotically Friedmann-Lemaitre-Robertson-Walker
universe in an infinite distance. As a result, we can show that the
gravitationally interacting branes explain free energy, entropy, temperature
and other physical quantities in these systems. This implies that the
microstates of this kind of brane system can be also understood in the p-soup
model.
