Does a cloud of strings affect shear viscosity bound?

Abstract

The Einstein AdS black brane with a cloud of strings background in context of massive gravity is introduced. There is a momentum dissipation on the boundary because of graviton mass on the bulk. The ratio of shear viscosity to entropy density is calculated for this solution. This value violates the KSS bound if we apply the Dirichlet boundary and regularity on the horizon conditions. Our result shows that this value is independent of the cloud of strings.

AdS Black Brane Solution Surrounded by Quintessence in Massive Gravity and KSS Bound

“…Since η s is proportional to the inverse squared of the coupling in feild theory side. Our outcome also shows that quintessence acts like Yang-Mills charge [30] and cloud of string [31].…”

The effect of three matters on KSS bound

“…This conjecture tells us that the ratio η/s has a lower bound, η s ≥ 4 π k B , for all relativistic quantum field theories at finite temperature without chemical potential [14] and can be interpreted as the Heisenberg uncertainty principle [11]. String cloud [41] and quintessence [20] in Einstein massive gravity does not contribute to the η s . However, this conjecture violates for higher derivative theories of gravity like the AdS Einstein-Gauss-Bonnet-Yang-Mills in the presence of string cloud and quintessence as we confirmed in section .…”

The Effect of Bulk Dimension in the presence of String Cloud on Viscosity Bound

“…Cloud of strings as a gravitational source studied for the first time in Einstein gravity [10] and in Lovelock gravity [11,12] as a generalization of Einstein gravity. In [13] we studied string clouds as a gravitational source in massive gravity in 4-dimensions but in this paper we want to study it in d-dimensions. Hierarchy problem and the brane-world gravity solutions [14,15] predict the existence of massive graviton.…”