Quantum Corrections to $\eta/s$ from JT Gravity

TL;DR

This paper investigates quantum gravitational effects on the shear viscosity to entropy ratio in holographic models, revealing temperature-dependent deviations from the universal bound due to quantum corrections from JT gravity.

Contribution

It introduces quantum corrections from JT gravity into the computation of ta/s, showing how these effects cause deviations from the universal value and depend on temperature.

Findings

ta/s has a minimum below 1/4 at semi-classical level.

ta/s increases at lower temperatures, exceeding the KSS bound.

Quantum corrections align shear viscosity with absorption cross-section calculations.

Abstract

We revisit the computation of the shear viscosity to entropy ratio $\eta/s$ at finite chemical potential in a holographic model that takes into account the quantum fluctuations in the IR region of near-extremal black branes. Such quantum corrections can be computed from JT gravity and generate non-trivial temperature dependence for $\eta/s$, which deviates from the universal $1/4\pi$ result. In the semi-classical regime, $\eta/s$ attains a minimum which is below the KSS bound, generated by the presence of the quantum effects. In the quantum regime at lower temperatures, $\eta/s$ increases and is well above the KSS bound. We also compare the shear viscosity to the quantum-corrected absorption cross-section of near-extremal black holes, and find agreement.