Viscous Properties of Strongly Interacting Matter at High Temperature

Abstract

Substantial collective flow is observed in collisions between large nuclei at high energy, and the data are well-reproduced by perfect fluid dynamics. In a separate development, calculation of the dimensionless ratio of shear viscosity $\eta$ to entropy density within AdS/CFT yields $\eta /s=1/4\pi$, which has been conjectured to be a lower bound for any physical system. It is shown that the transition from hadrons to quarks and gluons has behavior similar to helium, nitrogen, and water at and near their phase transitions in the ratio $\eta /s$. Conversely, there are indications that the ratio of bulk viscosity $\zeta$ to entropy density may have a maximum in the vicinity of the phase transition. Therefore it is possible that experimental measurements can pinpoint the location of the transition or rapid crossover in QCD via the ratios $\eta /s$ and $\zeta /s$ in addition to and independently of the equation of state.

Added section on gauge/gravity duality applied to viscosities

References in corpus (2)

• Universal properties of bulk viscosity near the QCD phase transition
• Bulk Viscosity of a Gas of Massless Pions

Cited by in corpus (8)

• Bulk Viscosity and Cavitation in Boost-Invariant Hydrodynamic Expansion
• Viscosity coefficients for hadron and quark-gluon phases
• The Bulk Channel in Thermal Gauge Theories
• Bulk viscosity of N=2* plasma
• Hydrodynamic Modeling and the QGP Shear Viscosity
• Viscous hydrodynamics with bulk viscosity -- uncertainties from relaxation time and initial conditions
• Energy-momentum tensor correlators and viscosity
• Remarks concerning bulk viscosity of hadron matter in relaxation time ansatz