# Rencontre de Physique des Particules 2015

15-16 janvier 2015
Institut Henri Poincaré
Fuseau horaire Europe/Paris

## Nonrenormalizablity of nonequilibrium quantum field theory in the classical approximation

16 janv. 2015 à 17:20
15m
Chair: Bira Van Kolck, Amphi Hermite (Institut Henri Poincaré)

### Chair: Bira Van Kolck, Amphi Hermite

#### Institut Henri Poincaré

11, rue Pierre et Marie Curie 75005 Paris

### 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.

### Auteurs principaux

Dr Bin Wu (IPhT, CEA/Saclay) Dr Francois Gelis (IPhT) Thomas Epelbaum (IPhT)

### Documents de présentation

 Transparents
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