ORIGINAL RESEARCH article
Front. Astron. Space Sci.
Sec. Nuclear Physics
Volume 12 - 2025 | doi: 10.3389/fspas.2025.1648066
This article is part of the Research TopicStrong and Weak Interactions in Compact StarsView all 7 articles
Bulk Viscosity of Two-Flavor Color Superconducting Quark Matter in Neutron Star Mergers
Provisionally accepted
- 1Washington University in St Louis, St. Louis, United States
- 2Byurakan Astrophysical Observatory, Byurakan, Armenia
- 3Institute of Theoretical Physics, Faculty of Physics and Astronomy, University of Wrocław, Wroclaw, Poland
- 4Frankfurt Institute for Advanced Studies, Frankfurt, Germany
Select one of your emails
You have multiple emails registered with Frontiers:
Notify me on publication
Please enter your email address:
If you already have an account, please login
You don't have a Frontiers account ? You can register here
This work investigates the bulk viscosity of warm, dense, neutrino-transparent, colorsuperconducting 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.
Keywords: neutron stars, neutrino interactions, quark matter, gravitational waves, Transport coefficients
Received: 16 Jun 2025; Accepted: 21 Jul 2025.
Copyright: © 2025 Alford, Harutyunyan, Sedrakian and Tsiopelas. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Armen Sedrakian, Institute of Theoretical Physics, Faculty of Physics and Astronomy, University of Wrocław, Wroclaw, Poland
Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.