Wilson renormalization group study of inverse symmetry breaking

For a large class of field theories there exist portions of parameter space for which the loop expansion predicts increased symmetry breaking at high temperature. Even though this behavior would clearly have far reaching implications for cosmology such theories have not been fully investigated in the literature. This is at least partially due to the counterintuitive nature of the result, which has led to speculations that it is merely an artifact of perturbation theory. To address this issue we study the simplest model displaying high temperature symmetry breaking using a Wilson renormalization group approach. We find that although the critical temperature is not reliably estimated by the loop expansion the total volume of parameter space which leads to the inverse phase structure is not significantly different from the perturbative prediction. We also investigate the temperature dependence of the coupling constants and find that they run approximately according to their one-loop $\beta$ functions at high temperature. Thus, in particular, the quartic coupling of ${\varphi }^4$ theory is shown to increase with temperature, in contrast with the behavior obtained in some previous studies.