  Relativistic effects in the thermodynamical properties of interacting
particle systems are investigated within the framework of the relativistic
direct interaction theory in various forms of dynamics. In the front form of
relativistic dynamics an exactly solvable model of a one-dimensional hard
spheres gas is formulated and an equation of state and thermodynamical
potentials for such a gas are found. Weakly-relativistic corrections to the
thermodynamical functions of the dilute gas with short-range interactions are
discussed on the basis of the approximately relativistic Hamiltonian function
in the instant form of dynamics.
