On the universality of thermodynamics and $\eta/s$ ratio for the charged Lovelock black branes

Abstract

We investigate general features of charged Lovelock black branes by giving a detailed description of geometrical, thermodynamic and holographic properties of charged Gauss-Bonnet (GB) black branes in five dimensions. We show that when expressed in terms of effective physical parameters, the thermodynamic behaviour of charged GB black branes is completely indistinguishable from that of charged Einstein black branes. Moreover, the extremal, near-horizon limit of the two classes of branes is exactly the same as they allow for the same AdS$_2\times R_3$, near-horizon, exact solution. This implies that, although in the UV the associated dual QFTs are different, they flow in the IR to the same fixed point. The calculation of the shear viscosity to entropy ratio $\eta/s$ confirms these results. Despite the GB dual plasma has in general a non-universal temperature-dependent $\eta/s$, it flows monotonically to the universal value $1/4\pi$ in the IR. For negative (positive) GB coupling constant, $\eta/s$ is an increasing (decreasing) function of the temperature and the flow respects (violates) the KSS bound.