The effective field theory approach to high temperature field theory can be used to study the phase transition in theories with spontaneously broken symmetry. I construct a sequence of two effective three–dimensional field theories which are valid on successively longer distance scales for a specific model: model: N charged scalars coupled to a U(1) gauge field. The resulting effective Lagrangi...

The finite-temperature one-loop effective potential for a scalar field in the static de Sitter space-time is obtained. Within this framework, by using zeta-function regularization, one can get, in the conformally invariant case, the explicit expression for the stress tensor anomaly. Its value turns out to depend on the thermal state of the system. This conclusion is different from the one deriv...

The effects of nonperturbative configurations at finite temperature are investigated for a real scalar field theory that exhibits a spontaneous symmetry breaking at zero temperature. In l+l dimensions we find a zero temperature phase transition due to kink-antikink pairs. In 3+1 dimensions we calculate the contribution of bubbles that have an interior region of different vacuum in the equilibri...

We investigate the two-loop gap equation for the thermal mass of hot massless gφ theory and find that the gap equation itself has an imaginary part which along with the finite terms contains divergent pieces too. This indicates that it is not possible to find the real finite thermal mass as a solution of the gap equation beyond g order of perturbation theory. PACS: 11.10.Wx Electronic address: ...