A finite temperature λφ4 model and A De Sitter — Friedmann transition in the early universe

We have analysed the finite temperature λφ⁴ model in the Robertson Walker metric, taking into consideration spontaneous symmetry breaking, particle production and symmetry recovery through phase transition under a high temperature, and found that it is possible to have a cosmological model free of singularities. Such a model begins in the singularity-free, horizon-free, Beltrami-Anti-de Sitter state. Continual production of particles keeps on raising its temperature until a critical temperature T_C is reached, when a phase change takes place, and the universe is transformed into a radiation-dominated, thermally-expanding Friedmann state. This phase transition corresponds to a big-bang without, however, an antecedent singularity.