Van!der Waals excluded volume model for Lorentz contracted rigid spheres

Conventional cluster and virial expansions are generalized to momentum dependent inter-particle potentials. The model with Lorentz contracted hard core potentials is considered, e.g, as hadron gas model. A Van der Waals-type model with a temperature dependent excluded volume is derived. Lorentz contraction effects at given temperature are stronger for light particles and make their effective excluded volume smaller than that of heavy ones. (C) 2000 Published by Elsevier Science B.V.