# Thermalization and Hydrodynamics of Two-Dimensional Quantum Field Theories

### Submission summary

 As Contributors: Luca Delacrétaz Arxiv Link: https://arxiv.org/abs/2105.02229v3 (pdf) Date accepted: 2022-02-28 Date submitted: 2022-02-04 03:35 Submitted by: Delacrétaz, Luca Submitted to: SciPost Physics Academic field: Physics Specialties: Condensed Matter Physics - Theory High-Energy Physics - Theory Approach: Theoretical

### Abstract

We consider 2d QFTs as relevant deformations of CFTs in the thermodynamic limit. Using causality and KPZ universality, we place a lower bound on the timescale characterizing the onset of hydrodynamics. The bound is determined parametrically in terms of the temperature and the scale associated with the relevant deformation. This bound is typically much stronger than $\frac{1}{T}$, the expected quantum equilibration time. Subluminality of sound further allows us to define a thermodynamic $C$-function, and constrain the sign of the $\mathcal T\bar{\mathcal T}$ term in EFTs.

Published as SciPost Phys. 12, 119 (2022)

### List of changes

List of changes:
- Added clarifications in Sec. 3 and 4.1.
- made corrections to Sec. 5.4 on the application to theories with large c_UV, and added references.