Bulk viscosity in a neutron star mantle

Understand

We study the bulk viscosity in two (anti-spaghetti and Swiss cheese) phases of non- spherical nuclei in the mantle of an oscillating neutron star near the boundary with the stellar core.

• The bulk viscosity is produced by non-equilibrium Urca neutrino emis- sion processes.
• In the mantle, the direct Urca process may be open (Gusakov et al., 2004) if neutrons and protons move in a periodic potential created by a lattice of non- spherical nuclei (which allows the nucleons to have large quasi-momenta and satisfy direct Urca momentum-conservation).
• This bulk viscosity can dominate over that due to the modified Urca process in the outer stellar core and over the shear viscosity.