$\delta$-Expansion at Finite Temperature

Abstract

We apply the $\delta$-expansion perturbation scheme to the $\lambda {\varphi }^4$ self-interacting scalar field theory in 3+1 D at finite temperature. In the $\delta$-expansion the interaction term is written as $\lambda ({\varphi }^2{)}^{1+\delta }$ and $\delta$ is considered as the perturbation parameter. We compute within this perturbative approach the renormalized mass at finite temperature at a finite order in $\delta$. The results are compared with the usual loop-expansion at finite temperature.

plain LaTeX, 11 pages, to be published in Braz. Journ. Phys