SYMMETRY NONRESTORATION AT HIGH TEMPERATURES

High temperature symmetry nonrestoration may have very important consequences in cosmology. Usually this phenomenon shows up in multi-field theories such as the O(N₁) × O(N₂) scalar model studied in this work. Here we use the δ expansion and the imaginary time formalism to evaluate thermal masses up to two-loop in a perturbative way. Apart from strongly supporting symmetry nonrestoration, our results reveal the possibility of other high temperature symmetry breaking patterns for which the last term in the breaking sequence is O(N₁ - 1) × O(N₂ - 1).