Speaker
Description
This work investigates the bulk viscosity of warm, dense,
neutrino-transparent, color-superconducting quark matter, where
damping of density oscillations in the kHz frequency range arises
from weak-interaction-driven direct Urca processes involving
quarks. We study the two-flavor red-green paired
color-superconducting (2SC) phase, while allowing for the presence
of unpaired strange quarks and blue color light quarks of all
flavors. Our calculations are based on the SU(3) Nambu-Jona-Lasinio
(NJL) model, extended to include both vector interactions and the
't Hooft determinant term. The primary focus is on how variations in
the NJL Lagrangian parameters - specifically, the diquark and vector
coupling strengths - affect both the static properties of quark
matter, such as its equation of state and composition, and its
dynamical behavior, including bulk viscosity and associated damping
timescales. We find that the bulk viscosity and corresponding
damping timescale can change by more than an order of magnitude upon
varying the vector coupling by a factor of two at high densities and
by a lesser degree at lower densities. This sensitivity primarily
arises from the susceptibility of 2SC matter, with a smaller
contribution from modifications to the weak interaction rates. In
comparison, changes in the diquark coupling have a more limited
impact. The damping of density oscillations in 2SC matter is similar
quantitatively to nucleonic matter and can be a leading mechanism of
dissipation in merging hybrid stars containing color superconducting
cores.
