On the importance of viscous dissipation and heat conduction in binary neutron-star mergers

Abstract

Inferring the properties of dense matter is one of the most exciting prospects from the measurement of gravitational waves from neutron star mergers. However, it will require reliable numerical simulations that incorporate viscous dissipation and energy transport if these can play a significant role within the survival time of the post-merger object. We calculate timescales for typical forms of dissipation and find that thermal transport and shear viscosity will not be important unless neutrino trapping occurs, which requires temperatures above about 10 MeV and gradients over lengthscales of 0.1 km or less. On the other hand, if direct-Urca processes remain suppressed, leaving modified-Urca processes to establish flavor equilibrium, then bulk viscous dissipation could provide significant damping to density oscillations observed right after the merger. When comparing with data from a state-of-the-art merger simulation we find that the bulk viscosity takes values close to its resonant maximum in a typical neutron-star merger, motivating a more careful assessment of the role of bulk viscous dissipation in the gravitational-wave signal from merging neutron stars.

6 pages, 4 figures

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• When Did the Remnant of GW170817 Collapse to a Black Hole?
• Causality of the Einstein-Israel-Stewart Theory with Bulk Viscosity
• When the entropy has no maximum: A new perspective on the instability of the first-order theories of dissipation
• Merger of two neutron stars: predictions from the two-families scenario
• Hybrid equation of state approach in binary neutron-star merger simulations
• Thermodynamics of Neutrons in a Magnetic Field and its Implications for Neutron Stars
• Formulating bulk viscosity for neutron star simulations
• Bulk Viscosity of Relativistic $npe\mu$ Matter in Neutron-Star Mergers
• Binary neutron star merger simulations with hot microscopic equations of state
• Holographic QCD in the NICER era
• Thermal effects on nuclear matter properties
• Dynamically screened strongly quantized electron transport in binary neutron-star merger
• Projecting the likely importance of weak-interaction-driven bulk viscosity in neutron star mergers
• Thermal aspects of neutron star mergers
• Interacting quark matter effects on the structure of compact stars
• Light scalars in neutron star mergers
• Light hyperclusters and hyperons in low-density hot stellar matter
• Non-perturbative Aspects of Quantum Field Theories from Holography
• Scaling of Small-Scale Dynamo Properties in the Rayleigh-Taylor Instability
• Equivalence of dissipative and dissipationless dynamics of interacting quantum systems with its application to the unitary Fermi gas