Orateur
Dr
Bin Wu
(IPhT, CEA/Saclay)
Description
Nonequilibrium quantum field theory in the classical statistical approximation (CSA) has a broad range of applications to understanding thermalization of systems with a large occupation number both in cosmology and in ultra-relativistic heavy-ion collisions. In my talk, I would like first to give a brief introduction to the CSA in the $g^2\phi^4$ theory. Then, I will present our discovery of nonrenormalizability of such an approximation (Phys. Rev. D 90, 065029 (2014)). I shall also show the Boltzmann equation in two types of classical approximations, which are equivalent to the CSA in the case that the distribution function $f$ satisfies $\frac{1}{g^2}\gg f\gg 1$. The numerical results to the Boltzmann equation in one of the classical limits presented in another paper of ours (arXiv:1409.0701, to appear in PRD) further confirm nonrenormalizability of the CSA. Besides, I would also like to discuss the features of forming a Bose-Einstein condensate in the classical approximations.
