SCREENED PERTURBATION-THEORY

A new perturbative scheme is proposed for the evaluation of the free e nergy density of field theories at finite temperature. The screened lo op expansion takes into account exactly the phenomenon of screening in thermal propagators. The approach is tested in the N-component scalar field theory at 2-loop level and also at 3-loop in the large-N limit. The perturbative series generated by the screened loop expansion show s much better numerical convergence than previous expansions generated in powers of the quartic coupling. (C) 1997 Elsevier Science B.V.