Bulk Viscosity of Quark-Gluon Plasma in Strong Magnetic Fields

Understand

We investigate the viscosities of the quark-gluon plasma in strong magnetic fields within the leading-log and lowest Landau level (LLL) approximations.

• We first show that the bulk viscosity in the direction parallel to the magnetic field is the only component that has a contribution from the quarks occupying the LLL.
• We then compute the bulk viscosity from the Kubo formula and find an intriguing quark-mass dependence as a consequence of a competition between the suppression of the bulk viscosity by conformal symmetry and an enhancement of the mean-free path by chirality conservation, which governs the behavior in the massless limit.
• The quark contribution to the viscosity along the magnetic field becomes larger than the one in the absence of a magnetic field.