Viscosities of anisotropic quark-gluon plasma

Abstract

We explore several methods for calculating the two shear viscosities and three bulk viscosities of magnetohydrodynamics for a quark-gluon plasma using improved holographic QCD. First we look at a method based on fluctuation equations. We work both with UV expansions and with a method based on the membrane paradigm. We calculate the shear viscosities, and describe some problems you stumble upon when calculating the bulk viscosities. Then we look at methods based on dually mimicking fluid equations, in this case Fick’s law and the entropy current equations, we manage to extract several viscosities, but there seems to be a restriction on which viscosities you can extract based on the zero temperature boost symmetry breaking. Lastly, we calculate the a magnetic field dependent bulk viscosities for analytic two-dimensional model related to a gravity dual of the ABJM model.