Condensation of interacting scalar bosons at finite temperatures

Thermodynamical properties of an interacting system of scalar bosons at finite temperatures are studied within the framework of a field-theoretical model containing the attractive and repulsive self-interaction terms. Self-consistency relations between the effective mass and thermodynamic functions are derived in the mean-field approximation. We show that for a sufficiently strong attractive interaction a first-order phase transition develops in the system via the formation of a scalar condensate. An interesting prediction of this model is that the condensed phase appears within a finite temperature interval and is characterized by a constant scalar density of Bose particles.