Two-loop calculation of the turbulent Prandtl number.

The turbulent Prandtl number has been calculated in the two-loop approximation of the epsilon expansion of the stochastic theory of turbulence. The strikingly small value obtained for the two-loop correction explains the good agreement of the earlier one-loop result with the experiment. This situation is drastically different from other available nontrivial two-loop results, which exhibit corrections of the magnitude of the one-loop term. The reason is traced to the mutual cancellation of additional divergences appearing in two dimensions, which have had a major effect on the results of previous calculations of other quantities.