$\eta/s$ in a strongly coupled QFT

TL;DR

This paper calculates the shear viscosity to entropy density ratio in a strongly coupled $O(N)$ $g\,\varphi^4$ quantum field theory, revealing a result similar to AdS/CFT predictions and demonstrating a versatile computational method.

Contribution

It introduces a method to compute $\,\eta/s$ in strongly coupled QFTs, showing results akin to string theory and applicable to other theories with modifications.

Findings

$\,\eta/s$ matches AdS/CFT results for strongly coupled theories

Method applicable to other quantum field theories

Reveals interesting features of the considered theory

Abstract

We consider $O(N)$ $g\varphi^4$ theory with the coupling $g$ being large, and calculate shear viscosity to entropy density ratio ($\eta/s$). The final result for $\eta/s$ has a form remarkably similar to that obtained from string theory calculations via the AdS/CFT conjecture. The method adopted can be used to compute quantities of interest in other theories as well with some modifications and reveals some very interesting features within the considered theory.