BULK VISCOSITY OF STRANGE QUARK MATTER, DAMPING OF QUARK STAR VIBRATION, AND THE MAXIMUM ROTATION RATE OF PULSARS

The bulk viscosity of strange quark matter is calculated in the light of new rate expressions for the reaction u + s <-> d + u. The results are orders of magnitude larger than previously assumed, in particular, in the limit of high amplitude perturbations. This has important consequences for the vibration and rotation properties of strange stars and neutron stars with quark cores, implying rapid damping of stellar vibrations and suppression of nonaxisymmetric instabilities for rapidly spinning pulsars, probably decreasing the minimum rotation period to the Keplerian limit of 0.6 ms.