Informal Pizza Seminar

Holographic hydrodynamics at finite coupling

Aninda Sinha

Perimeter Institute

The ratio of shear viscosity to entropy density is a quantity of great interest in RHIC, LHC physics. AdS/CFT methods have led to the famous viscosity bound η/s≥ 1/(4π). For the first time, this is rigorously established in the context of AdS/CFT with adjoint matter in N=4 SYM. This is achieved by consider the full set of relevant higher derivative corrections at order R⁴ including the 5-form flux in IIB string theory. It is further shown that the compact manifold decouples from the equations of motion even after including the correction, thereby leading to universality in all hydrodynamic quantities at this order. When one incorporates fundamental matter, the higher derivative corrections begin at R² order. This leads to a violation of the bound at order 1/N. Various examples are considered using the holographic Weyl anomaly and in all cases, this bound is found to be violated.