Transition Temperature of Dilute, Weakly Repulsive Bose Gas

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Within a quasiparticle framework, we reconsider the issue of computing the Bose-Einstein condensation temperature (Tc) in a weakly non-ideal Bose gas. The main result of this and previous investigations is that Tc increases with the scattering length a, with the leading dependence being either linear or log-linear in a. The calculation of Tc reduces to that of computing the excitation spectrum near the transition. We report two approaches to regularizing the infrared divergence at the transition point. One leads to a a√|a|-like shift in Tc, and the other allows numerical calculations for the shift.