Hyperneutron Stars from an Ab Initio Calculation

The equation of state (EOS) of neutron matter plays a decisive role in understanding the neutron star properties and the gravitational waves from neutron star mergers. At sufficient densities, the appearance of hyperons generally softens the EOS, leading to a reduction in the maximum mass of neutron...

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Main Authors: Hui Tong, Serdar Elhatisari, Ulf-G. Meißner​
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal
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Online Access:https://doi.org/10.3847/1538-4357/adba47
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author Hui Tong
Serdar Elhatisari
Ulf-G. Meißner​
author_facet Hui Tong
Serdar Elhatisari
Ulf-G. Meißner​
author_sort Hui Tong
collection DOAJ
description The equation of state (EOS) of neutron matter plays a decisive role in understanding the neutron star properties and the gravitational waves from neutron star mergers. At sufficient densities, the appearance of hyperons generally softens the EOS, leading to a reduction in the maximum mass of neutron stars well below the observed values of about 2 M _⊙ . Even though repulsive three-body forces are known to solve this so-called “hyperon puzzle,” so far performing ab initio calculations with a substantial number of hyperons for neutron star properties has remained elusive. Starting from the newly developed auxiliary field quantum Monte Carlo algorithm to simulate hyperneutron matter without any sign oscillations, we derive three distinct EOSs by employing the state-of-the-art nuclear lattice effective field theory. We include N Λ, ΛΛ two-body forces, NN Λ, and N ΛΛ three-body forces. Consequently, we determine essential astrophysical quantities such as the neutron star mass, radius, tidal deformability, and universal I –Love– Q relation. The maximum mass, radius, and tidal deformability of a 1.4 M _⊙ neutron star are predicted to be 2.17(1)(1) M _⊙ , R _1.4 _M _⊙  = 13.10(1)(7) km, and ${{\rm{\Lambda }}}_{1.4{M}_{\odot }}=597(5)(18)$ , respectively, based on our most realistic EOS. These predictions are in good agreement with the latest astrophysical constraints derived from observations of massive neutron stars, gravitational waves, and joint mass–radius measurements. In addition, for the first time in ab initio calculations, we investigate both nonrotating and rotating neutron star configurations. The results indicate that the impact of rotational dynamics on the maximum mass is small, regardless of whether hyperons are present in the EOS or not.
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spelling doaj-art-3226de1b7c434bedb645261aebce106b2025-08-20T02:54:32ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01982216410.3847/1538-4357/adba47Hyperneutron Stars from an Ab Initio CalculationHui Tong0https://orcid.org/0000-0002-9666-6098Serdar Elhatisari1https://orcid.org/0000-0002-7951-1991Ulf-G. Meißner​2https://orcid.org/0000-0003-1254-442XHelmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universität Bonn , D-53115 Bonn, Germany ; htong@uni-bonn.de, meissner@hiskp.uni-bonn.deFaculty of Natural Sciences and Engineering, Gaziantep Islam Science and Technology University , Gaziantep 27010, Turkey ; selhatisari@gmail.com; Interdisciplinary Research Center for Industrial Nuclear Energy (IRC-INE), King Fahd University of Petroleum and Minerals (KFUPM) , 31261 Dhahran, Saudi ArabiaHelmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universität Bonn , D-53115 Bonn, Germany ; htong@uni-bonn.de, meissner@hiskp.uni-bonn.de; Institute for Advanced Simulation (IAS-4) , Forschungszentrum Jülich, D-52425 Jülich, Germany; Center for Advanced Simulation and Analytics (CASA) , Forschungszentrum Jülich, D-52425 Jülich, Germany; Peng Huanwu Collaborative Center for Research and Education, International Institute for Interdisciplinary and Frontiers, Beihang University , Beijing 100191, People’s Republic of ChinaThe equation of state (EOS) of neutron matter plays a decisive role in understanding the neutron star properties and the gravitational waves from neutron star mergers. At sufficient densities, the appearance of hyperons generally softens the EOS, leading to a reduction in the maximum mass of neutron stars well below the observed values of about 2 M _⊙ . Even though repulsive three-body forces are known to solve this so-called “hyperon puzzle,” so far performing ab initio calculations with a substantial number of hyperons for neutron star properties has remained elusive. Starting from the newly developed auxiliary field quantum Monte Carlo algorithm to simulate hyperneutron matter without any sign oscillations, we derive three distinct EOSs by employing the state-of-the-art nuclear lattice effective field theory. We include N Λ, ΛΛ two-body forces, NN Λ, and N ΛΛ three-body forces. Consequently, we determine essential astrophysical quantities such as the neutron star mass, radius, tidal deformability, and universal I –Love– Q relation. The maximum mass, radius, and tidal deformability of a 1.4 M _⊙ neutron star are predicted to be 2.17(1)(1) M _⊙ , R _1.4 _M _⊙  = 13.10(1)(7) km, and ${{\rm{\Lambda }}}_{1.4{M}_{\odot }}=597(5)(18)$ , respectively, based on our most realistic EOS. These predictions are in good agreement with the latest astrophysical constraints derived from observations of massive neutron stars, gravitational waves, and joint mass–radius measurements. In addition, for the first time in ab initio calculations, we investigate both nonrotating and rotating neutron star configurations. The results indicate that the impact of rotational dynamics on the maximum mass is small, regardless of whether hyperons are present in the EOS or not.https://doi.org/10.3847/1538-4357/adba47Nuclear physics
spellingShingle Hui Tong
Serdar Elhatisari
Ulf-G. Meißner​
Hyperneutron Stars from an Ab Initio Calculation
The Astrophysical Journal
Nuclear physics
title Hyperneutron Stars from an Ab Initio Calculation
title_full Hyperneutron Stars from an Ab Initio Calculation
title_fullStr Hyperneutron Stars from an Ab Initio Calculation
title_full_unstemmed Hyperneutron Stars from an Ab Initio Calculation
title_short Hyperneutron Stars from an Ab Initio Calculation
title_sort hyperneutron stars from an ab initio calculation
topic Nuclear physics
url https://doi.org/10.3847/1538-4357/adba47
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AT serdarelhatisari hyperneutronstarsfromanabinitiocalculation
AT ulfgmeißner hyperneutronstarsfromanabinitiocalculation