The 2PI effective action at four loop order in $\varphi^4$ theory

Understand

It is well known that perturbative pressure calculations show poor convergence.

• Calculations using a two particle irreducible (2PI) effective action show improved convergence at the 3 loop level, but no calculations have been done at 4 loops.
• We consider the 2PI effective theory for a symmetric scalar theory with quartic coupling in 4-dimensions.
• We calculate the pressure and two different non-perturbative vertices as functions of coupling and temperature.