Hot Scalar Theory in Large N: Bose-Einstein Condensation

I review the Bose-Einstein condensation phase transition of dilute gases of cold atoms, for particle theorists acquainted with methods of field theory at finite temperature. I then discuss how the dependence of the phase transition temperature on the interaction strength can be computed in the large N approximation.Comment: Talk presented at SEWM 2000. 5 pages, 2 figure

Gluon Bremsstrahlung in Weakly-Coupled Plasmas

I report on some theoretical progress concerning the calculation of gluon bremsstrahlung for very high energy particles crossing a weakly-coupled quark-gluon plasma. (i) I advertise that two of the several formalisms used to study this problem, the BDMPS-Zakharov formalism and the AMY formalism (the latter used only for infinite, uniform media), can be made equivalent when appropriately formulated. (ii) A standard technique to simplify calculations is to expand in inverse powers of logarithms $\ln(E/T)$. I give an example where such expansions are found to work well for $\omega/T \gtrsim 10$ where $\omega$ is the bremsstrahlung gluon energy. (iii) Finally, I report on perturbative calculations of $\hat q$.Comment: 4 pages, 2 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee [change from v2: minor changes for publication

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.Comment: 21 pages, 7+1 figures; an embarassing factor of 2 has been corrected in the evaluation of one diagram, changing the previous +18% result for the NLO correction to -26