Nonperturbative study of inverse symmetry breaking at high temperatures - art. no. 125016

The optimized linear delta expansion is applied to multifield O(N-1) X O(N- 2) scalar theories at high temperatures. Using the imaginary time formalism the thermal masses are evaluated perturbatively up to order delta(2) which considers consistently all two-loop contributions. A variational procedure associated with the method generates nonperturbative results which are use d to search for parameter values for inverse symmetry breaking (or symmetry nonrestoration) at high temperatures, Our results are compared with the on es obtained by the one-loop perturbative approximation, the gap equation so lutions and the renormalization group approach, showing good agreement with the latter method. Apart from strongly supporting inverse symmetry breakin g (or 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(N-1-1) X O(N-2-1).