Thermodynamics of relativistic Newton-Wigner particle in external potential field

Thermodynamic properties of relativistic spinless particle described by the Klein Gordon equation have been studied using the Newton Wigner theory of particle in external potential field. Concept of Wiener path integral was extended on relativistic case. A new path integral Monte -Carlo method was developed for relativistic particle in external potential field. The bounds of applicability of available analytical approaches and related results have been specified by comparison with Monte Carlo calculations. Developed path integral formalism can be directly extended on systems of many identical Newton Wigner particles, which interact with external field and each other.