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Viscous Dissipation and Heat Conduction in Binary Neutron-Star Mergers
Mark G Alford1, Luke Bovard2, Matthias Hanauske2,3
1Physics Department, Washington University, St. Louis, Missouri 63130, USA.
Physical Review Letters
|February 14, 2018
Summary
Understanding neutron star mergers requires accounting for viscous dissipation. Bulk viscosity, not thermal transport or shear viscosity, significantly damps post-merger oscillations, influencing gravitational wave signals.
Area of Science:
- Astrophysics
- Nuclear Physics
- Gravitational Wave Astronomy
Background:
- Neutron star mergers are key to understanding dense matter properties.
- Accurate simulations require incorporating viscous dissipation and energy transport.
- These factors influence the post-merger object's survival time.
Purpose of the Study:
- To calculate time scales for various dissipation mechanisms in neutron star mergers.
- To assess the significance of thermal transport, shear viscosity, and bulk viscosity.
- To determine the impact of these processes on gravitational wave signals.
Main Methods:
- Numerical simulations of neutron star mergers.
- Calculation of dissipation time scales under different physical conditions.
- Comparison of theoretical findings with state-of-the-art merger simulations.
Main Results:
- Thermal transport and shear viscosity are significant only under extreme conditions (neutrino trapping, T > 10 MeV, small length scales).
- Bulk viscous dissipation significantly damps post-merger density oscillations if direct-Urca processes are suppressed.
- Bulk viscosity values in typical mergers approach their resonant maximum.
Conclusions:
- Bulk viscous dissipation plays a crucial role in the dynamics of merging neutron stars.
- The damping effect of bulk viscosity on density oscillations is substantial.
- Further investigation into bulk viscosity's impact on gravitational wave signals is warranted.
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