Hydrodynamics of the cascading plasma

Abstract

The cascading gauge theory of Klebanov et al. realizes a soluble example of gauge/string correspondence in a non-conformal setting. Such a gauge theory has a strong coupling scale Λ, below which it confines with a chiral symmetry breaking. A holographic description of a strongly coupled cascading gauge theory plasma is represented by a black brane solution of type IIB supergravity on a conifold with fluxes. A characteristic parameter controlling the high temperature expansion of such plasma is Q ≃ ( ln T Λ ) − 1 . In this paper we study the speed of sound and the bulk viscosity of the cascading gauge theory plasma to order O ( Q 4 ) . We find that the bulk viscosity satisfies the bound conjectured in arXiv:0708.3459. We comment on difficulties of computing the transport coefficients to all orders in Q . Previously, it was shown that a cascading gauge theory plasma undergoes a first-order deconfinement transition with unbroken chiral symmetry at T critical = 0.6141111 ( 3 ) Λ . We show here that a deconfined chirally symmetric phase becomes perturbatively unstable at T unstable = 0.8749 ( 0 ) T critical . Near the unstable point the specific heat diverges as c V ∼ | 1 − T unstable T | − 1 / 2 .