# Quark Matter 2018

May 13 – 19, 2018
Venice, Italy
Europe/Zurich timezone
The organisers warmly thank all participants for such a lively QM2018! See you in China in 2019!

## Nonequilibrium viscous correction and bulk viscosity in the relaxation time approximation

May 15, 2018, 5:00 PM
2h 40m
First floor and third floor (Palazzo del Casinò)

### First floor and third floor

#### Palazzo del Casinò

Poster Initial state physics and approach to equilibrium

### Speaker

Alina Czajka (McGill University)

### Description

We present the correct form of the nonequilibrium viscous correction to the phase space density in the relaxation time approximation that properly takes into account the space-time dependence of the thermal mass. We also investigate the impact the correction has on the bulk viscosity. This correction automatically satisfies the Landau matching condition and energy-momentum conservation. It also makes the appearance of the Callan-Symanzyk $\beta_\lambda$-function natural in the bulk viscosity calculation. The bulk viscosity has the expected parametric form for the Boltzmann gas, while for the Bose-Einstein case, it is affected by the cut-off of infrared divergences. This may be an indication that the relaxation time approximation is too crude to obtain the correct form of the bulk viscosity for quantum gases.

Content type Theory Presenter name already specified

### Primary author

Alina Czajka (McGill University)

### Co-authors

Hauksson Sigtryggur (McGill University) Chun Shen (Brookhaven National Laboratory) Sangyong Jeon (McGill University) Charles Gale (McGill University)