On the physics of λφ4 in aℝ2×S 1 space

The physics of λφ⁴ quantum field theory in a space with a closed dimension (?²×S ¹) is studied on the basis of a varitional approach, which supports the existence of two interacting phases of the minkowskian λφ⁴ on nonperturbative grounds. As the lengthL of the closed dimension decreases (1/L becomes the relevant scale), triviality restoration is encountered in the “precarious” phase, as well as symmetry restoration in the “autonomous” phase. The close relation to the finite temperature formalism allows to uncover a temperature symmetry restoration of theT=0 spontaneously broken phase.