Screened perturbation theory at four loops
  We study the thermodynamics of massless phi-fourth theory using screened perturbation theory, which is a way to systematically reorganise the perturbative series. The free energy and pressure are calculated through four loops in a double expansion in powers of g^2 and m/T, where m is a thermal mass of order gT. The result is truncated at order g^7. We find that the convergence properties are significantly improved compared to the weak-coupling expansion. 
Lars Kyllingstad