Hydrodynamics of the cascading plasma

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(Q4). 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 Tcritical = 0.6141111(3)Λ. We show here that a deconfined chirally symmetric phase becomes perturbatively unstable at Tunstable = 0.8749(0)Tcritical. Near the unstable point the specific heat diverges as cV ∼ |1− Tunstable T |−1/2.