Emergence of microphysical bulk viscosity in binary neutron star post-merger dynamics
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arXiv
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| Main Authors: | , , , , , |
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| Format: | Preprint |
| Published: |
2022
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| _version_ | 1866910584775114752 |
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| author | Most, Elias R. Haber, Alexander Harris, Steven P. Zhang, Ziyuan Alford, Mark G. Noronha, Jorge |
| author_facet | Most, Elias R. Haber, Alexander Harris, Steven P. Zhang, Ziyuan Alford, Mark G. Noronha, Jorge |
| contents | In nuclear matter in isolated neutron stars, the flavor content (e.g., proton fraction) is subject to weak interactions, establishing flavor ($β$-)equilibrium. However, there can be deviations from this equilibrium during the merger of two neutron stars. We study the resulting out-of-equilibrium dynamics during the collision by incorporating direct and modified Urca processes (in the neutrino-transparent regime) into general-relativistic hydrodynamics simulations with a simplified neutrino transport scheme. We demonstrate how weak-interaction-driven bulk viscosity in post-merger simulations can emerge and assess the bulk viscous dynamics of the resulting flow. We further place limits on the impact on the post-merger gravitational wave strain. Our results show that weak-interaction-driven bulk viscosity can potentially lead to a phase shift of the post-merger gravitational wave spectrum, although the effect is currently on the same level as the numerical errors of our simulation. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2207_00442 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | Emergence of microphysical bulk viscosity in binary neutron star post-merger dynamics Most, Elias R. Haber, Alexander Harris, Steven P. Zhang, Ziyuan Alford, Mark G. Noronha, Jorge High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology Nuclear Theory In nuclear matter in isolated neutron stars, the flavor content (e.g., proton fraction) is subject to weak interactions, establishing flavor ($β$-)equilibrium. However, there can be deviations from this equilibrium during the merger of two neutron stars. We study the resulting out-of-equilibrium dynamics during the collision by incorporating direct and modified Urca processes (in the neutrino-transparent regime) into general-relativistic hydrodynamics simulations with a simplified neutrino transport scheme. We demonstrate how weak-interaction-driven bulk viscosity in post-merger simulations can emerge and assess the bulk viscous dynamics of the resulting flow. We further place limits on the impact on the post-merger gravitational wave strain. Our results show that weak-interaction-driven bulk viscosity can potentially lead to a phase shift of the post-merger gravitational wave spectrum, although the effect is currently on the same level as the numerical errors of our simulation. |
| title | Emergence of microphysical bulk viscosity in binary neutron star post-merger dynamics |
| topic | High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology Nuclear Theory |
| url | https://arxiv.org/abs/2207.00442 |