On the thermodynamic parameters of an adiabatically isolated bogy

Main thermodynamic functions for an adiabatically isolated body with a constant internal energy have been determined within the formalism of covariant quantum theory with reparameterization invariance of intrinsic time. The modification does not change the dynamic content of the theory on the classical level; however, it makes it possible to determine the unitary evolution operator in the quantum theory. In this operator, intrinsic time is a measure of internal motion of a body. A transition to statistical mechanics is performed by Wick rotation of intrinsic time in a complex plane. As a result, representation of the partition function of an isolated body in the form of Euclidean functional integral over the space of closed trajectories in the configuration space is obtained. The average reciprocal temperature and free energy, which underlie the thermal mechanics of an adiabatically isolated body, are determined for a specified internal energy.