The gravitational polarization tensor of thermal $\lambda {\varphi }^4$ theory

Abstract

The low-momentum structure of the gravitational polarization tensor of an ultrarelativistic plasma of scalar particles with $\lambda {\varphi }^4$ interactions is evaluated in a two-loop calculation up to and including order ${\lambda }^{3/2}$. This turns out to require an improved perturbation theory which resums a local thermal mass term as well as nonlocal hard-thermal-loop vertices of scalar and gravitational fields.

15 pages and 6 figures, uu-encoded postscript file