Bulk viscosity of two-color superconducting quark matter in neutron star mergers

Mark Alford; Arus Harutyunyan; Armen Sedrakian; Stefanos Tsiopelas

doi:10.1103/PhysRevD.110.L061303

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Bulk viscosity of two-color superconducting quark matter in neutron star mergers

Mark Alford, Arus Harutyunyan, Armen Sedrakian, Stefanos Tsiopelas

DOI 10.1103/PhysRevD.110.L061303 · Physical Review D

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Abstract

We study the bulk viscosity of moderately hot and dense, neutrino-transparent color superconducting quark matter arising from weak-interaction-driven direct URCA processes. The quark matter is modeled using the Nambu–Jona-Lasinio model improved to account for vector and ’t Hooft interactions as well as antisymmetric pairing among the red/green up and down quarks. The unpaired excitations are the strange quarks and the blue up or down quarks. We compute the relaxation rates associated with d- and s-quark decay and electron capture processes on the u quark for blue color. The resulting bulk viscosity for density oscillations in the 1–10 kHz range shows a resonant peak at T∼5 MeV, and the damping time may drop below 10 ms. This is short enough to affect the postmerger evolution and is very similar to the damping predicted in nuclear matter.