Higher derivative effects on eta/s at finite chemical potential

TL;DR

This paper investigates how higher derivative corrections in five-dimensional supergravity influence the shear viscosity to entropy density ratio at finite chemical potential, revealing potential violations of the universal bound.

Contribution

It introduces four-derivative corrections in supergravity and analyzes their impact on eta/s at finite chemical potential, showing bound violations.

Findings

Higher derivative terms cause eta/s to violate the bound.

Chemical potential amplifies the violation of eta/s bound.

Corrections are 1/N effects in the holographic dual.

Abstract

We examine the effects of higher derivative corrections on eta/s, the ratio of shear viscosity to entropy density, in the case of a finite R-charge chemical potential. In particular, we work in the framework of five-dimensional N =2 gauged supergravity, and include terms up to four derivatives, representing the supersymmetric completion of the Chern-Simons term A \wedge Tr (R \wedge R). The addition of the four-derivative terms yields a correction which is a 1/N effect, and in general gives rise to a violation of the eta/s bound. Furthermore, we find that, once the bound is violated, turning on the chemical potential only leads to an even larger violation of the bound.