Five-Loop Critical Temperature Shift in Weakly Interacting Homogeneous   Bose-Einstein Condensate
  Using variational perturbation theory, we calculate the shift in the critical temperature T_c up to five loops to lowest order in the scattering length a and find Delta T_c/T_c^{(0)} approx (1.14\pm0.11)an^{1/3}, where n is the particle density. Our result is lower than the latest Monte Carlo result (1.32\pm0.02)an^{1/3}. 
H. Kleinert