Higher derivative effects on η/s at finite chemical potential

We examine the effects of higher derivative corrections on η/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∧Tr(R∧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 η/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.