T_c for dilute Bose gases: beyond leading order in 1/N
  Baym, Blaizot, and Zinn-Justin have recently used the large N approximation to calculate the effect of interactions on the transition temperature of dilute Bose gases. We extend their calculation to next-to-leading-order in 1/N and find a relatively small correction of -26% to the leading-order result. This suggests that the large N approximation works surprisingly well in this application. 
Peter Arnold and Boris Tomasik