Impact of magnetic field-driven anisotropies on the equation of state probed in neutron star mergers

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Main Authors: Most, Elias R., Peterson, Jeffrey, Scurto, Luigi, Pais, Helena, Dexheimer, Veronica
Format: Preprint
Published: 2025
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author Most, Elias R.
Peterson, Jeffrey
Scurto, Luigi
Pais, Helena
Dexheimer, Veronica
author_facet Most, Elias R.
Peterson, Jeffrey
Scurto, Luigi
Pais, Helena
Dexheimer, Veronica
contents Binary neutron star mergers can produce extreme magnetic fields, some of which can lead to strong magnetar-like remnants. While strong magnetic fields have been shown to affect the dynamics of outflows and angular momentum transport in the remnant, they can also crucially alter the properties of nuclear matter probed in the merger. In this work, we provide a first assessment of the latter, determining the strength of the pressure anisotropy caused by Landau level quantization and the anomalous magnetic moment. To this end, we perform the first numerical relativity simulation with a magnetic polarization tensor and a magnetic-field-dependent equation of state using a new algorithm we present here, which also incorporates a mean-field dynamo model to control the magnetic field strength present in the merger remnant. Our results show that -- in the most optimistic case -- corrections to the anisotropy can be in excess of $10\%$, and are potentially largest in the outer layers of the remnant. This work paves the way for a systematic investigation of these effects.
format Preprint
id arxiv_https___arxiv_org_abs_2506_21696
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Impact of magnetic field-driven anisotropies on the equation of state probed in neutron star mergers
Most, Elias R.
Peterson, Jeffrey
Scurto, Luigi
Pais, Helena
Dexheimer, Veronica
High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
Nuclear Theory
Binary neutron star mergers can produce extreme magnetic fields, some of which can lead to strong magnetar-like remnants. While strong magnetic fields have been shown to affect the dynamics of outflows and angular momentum transport in the remnant, they can also crucially alter the properties of nuclear matter probed in the merger. In this work, we provide a first assessment of the latter, determining the strength of the pressure anisotropy caused by Landau level quantization and the anomalous magnetic moment. To this end, we perform the first numerical relativity simulation with a magnetic polarization tensor and a magnetic-field-dependent equation of state using a new algorithm we present here, which also incorporates a mean-field dynamo model to control the magnetic field strength present in the merger remnant. Our results show that -- in the most optimistic case -- corrections to the anisotropy can be in excess of $10\%$, and are potentially largest in the outer layers of the remnant. This work paves the way for a systematic investigation of these effects.
title Impact of magnetic field-driven anisotropies on the equation of state probed in neutron star mergers
topic High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
Nuclear Theory
url https://arxiv.org/abs/2506.21696