Probing In-Medium Neutron-to-Dark-Fermion Conversion with Multimessenger Neutron Star Observations
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 Gχ. We consider masses mχ 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 mχ=939--$1500$ MeV and Gχ=1--$100$ fm2 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⊙ 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 mχ=939--$1300$ MeV and Gχ=1--$11$ fm2. 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⊙ 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.
Related
- Evaluating KAGRA upgrade scenarios for multimessenger observations of binary neutron stars
- Probing fundamental physics with ALMA2040 mm-wavelength observations of neutron stars
- Multimessenger Constraints on the Central Engine in SN 2023ixf: Neutron Star or Black Hole?
- Multimessenger Probes of Primordial Black Holes with Gravitational Wave and 21 cm Observations
- Landau-Zener formula and resonant axion conversion in neutron star magnetospheres
BibTeX
@misc{karkevandi2026probing,
title = {{Probing In-Medium Neutron-to-Dark-Fermion Conversion with Multimessenger Neutron Star Observations}},
author = {Davood Rafiei Karkevandi and Mahboubeh Shahrbaf and Hamid Reza Moshfegh and Reza Karimi and Gordon Baym},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.34234},
eprint = {2610.34234},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.34234},
}
RIS
TY - UNPB
TI - Probing In-Medium Neutron-to-Dark-Fermion Conversion with Multimessenger Neutron Star Observations
AU - Davood Rafiei Karkevandi
AU - Mahboubeh Shahrbaf
AU - Hamid Reza Moshfegh
AU - Reza Karimi
AU - Gordon Baym
PY - 2026
DA - 2026/10/25
PB - arXiv
DO - 10.48550/arxiv.2610.34234
UR - https://arxiv.org/abs/2610.34234
AB - 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_⊙ 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_⊙ 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.
ER -