36 research outputs found
Damping of sound waves in superfluid nucleon-hyperon matter of neutron stars
We consider sound waves in superfluid nucleon-hyperon matter of massive
neutron-star cores. We calculate and analyze the speeds of sound modes and
their damping times due to the shear viscosity and non-equilibrium weak
processes of particle transformations. For that, we employ the dissipative
relativistic hydrodynamics of a superfluid nucleon-hyperon mixture, formulated
recently [M.E. Gusakov and E.M. Kantor, Phys. Rev. D78, 083006 (2008)]. We
demonstrate that the damping times of sound modes calculated using this
hydrodynamics and the ordinary (nonsuperfluid) one, can differ from each other
by several orders of magnitude.Comment: 15 pages, 5 figures, Phys. Rev. D accepte
Bulk viscosity of superfluid hyperon stars
We calculated bulk viscosity due to non-equilibrium weak processes in
superfluid nucleon-hyperon matter of neutron stars. For that, the dissipative
relativistic hydrodynamics, formulated in paper [1] for superfluid mixtures,
was extended to the case when both nucleons and hyperons are superfluid. It was
demonstrated that in the most general case (when neutrons, protons, Lambda, and
Sigma^{-} hyperons are superfluid), non-equilibrium weak processes generate
sixteen bulk viscosity coefficients, with only three of them being independent.
In addition, we corrected an inaccuracy in a widely used formula for the bulk
viscosity of non-superfluid nucleon-hyperon matter.Comment: 22 pages, 2 figure