{
  "abstract": "Neutron stars provide a natural environment for probing in-medium neutron-to-dark-fermion conversion and its impact on the dense-matter equation of state (EOS). We use multimessenger neutron star observations to map excluded and not-excluded regions of dark-sector parameter space for an EOS ensemble within a non-linear $σ$--$ω$--$ρ$ relativistic mean-field (RMF) framework and determine their overlap across the ensemble. We include a fermionic dark component with repulsive self-interactions of strength $G_χ$. We consider masses $m_χ$ near the neutron mass and heavier states accessible in neutron star cores at sufficiently large neutron chemical potentials. To reduce sensitivity to the nucleonic EOS within this framework, we scan $m_χ=939$--$1500$ MeV and $G_χ=1$--$100$ fm$^2$ across 21 nucleonic EOSs: a main baseline set of 13 EOSs and soft and stiff limiting cases. Stellar sequences are tested against the requirement that the EOS support at least $2M_\\odot$ neutron stars, GW170817 tidal-deformability bounds, and NICER mass--radius constraints, considering the Illinois--Maryland and X-PSI/Amsterdam inference sets separately. For the full ensemble of 21 EOSs, both NICER analyses identify similar regions excluded by all EOSs, with approximate minimum--maximum extents of $m_χ=939$--$1300$ MeV and $G_χ=1$--$11$ fm$^2$. Unlike the full 21-EOS ensemble, the main baseline set has a common not-excluded region whose extent depends on the NICER analysis. The soft and stiff limiting cases show how these regions shift when the nucleonic EOS predicts a maximum neutron star mass near $2M_\\odot$ or large tidal deformabilities. Across these 21 calibrated nucleonic RMF EOSs, weak dark-sector repulsion is robustly disfavored across a broad dark-fermion mass range, while the extent of the remaining not-excluded region depends on the NICER analysis and baryonic EOS stiffness.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.34234",
  "author_total": 5,
  "authors": [
    {
      "name": "Davood Rafiei Karkevandi"
    },
    {
      "name": "Mahboubeh Shahrbaf"
    },
    {
      "name": "Hamid Reza Moshfegh"
    },
    {
      "name": "Reza Karimi"
    },
    {
      "name": "Gordon Baym"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/05w4ea3dqtkxb.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.34234",
  "fulltext_url": null,
  "id": "05w4ea3dqtkxb",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.34234",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.HE"
    ],
    [
      "arxiv",
      "nucl-th"
    ],
    [
      "openalex",
      "3103|Pulsars and Gravitational Waves Research"
    ]
  ],
  "openalex": "W7223903832",
  "pdf_url": "https://arxiv.org/pdf/2610.34234",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-25",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/05w4ea3dqtkxb.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:35:35Z",
      "native_id": "2610.34234",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.34234"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "physics",
      "origin": "arxiv:nucl-th",
      "subfield": "nuclear"
    }
  ],
  "title": "Probing In-Medium Neutron-to-Dark-Fermion Conversion with Multimessenger Neutron Star Observations",
  "title_text": "Probing In-Medium Neutron-to-Dark-Fermion Conversion with Multimessenger Neutron Star Observations",
  "type": "preprint",
  "updated_at": "2026-10-30T12:35:35Z",
  "url": "https://research.draconitic.com/paper/05w4ea3dqtkxb",
  "venue": "arXiv",
  "versions": []
}