The Gaussian approximation for interacting charged scalar fields

The Gaussian effective-potential approach is used to explore the physics of charged λ(φ+φ)2 theory in four space-time dimensions. We find and employ an appropriate trial system parametrized by two effective masses, for obtaining an adequate Gaussian effective potential under conditons of the global U (1) symmetry and the finite temperature. A simple renormalization accompanied by an explicit dimensional regularization, is employed. We find that the nontrivial approach arises from a bare coupling constant of a negative infinitesimal form, well known in the noncharged case as "precarious". The behavior of this solution is discussed, and the symmetry breaking due to background charge density is discovered.