Dark matter in neutron stars: two-fluid f-mode oscillations in full general relativity
Abstract
A dark-matter core and a soft nuclear equation of state can produce similar mass--radius signatures, motivating a complementary probe through the f-mode spectrum. We compute quadrupolar f-mode frequencies and gravitational-wave damping times in full general relativity for cold, nonrotating neutron stars admixed with self-interacting bosonic dark matter (DM). Our two-fluid survey spans 21 nuclear equations of state covering nucleonic, hyperonic, Δ-admixed, and combined hyperon--Δ compositions at FDM=1--20%. The main sequences use λ=π and boson masses of $500$ and 100 MeV for the core and halo studies, respectively. Independent normal-matter (NM) and DM displacements couple through the metric, yielding NM-led and DM-led f-mode branches whose radiative damping is determined by outgoing-wave boundary conditions. At 1.4 M⊙, the core DM-led damping time decreases from order 103 s at FDM=1% to order 1 s at 20%, approximately following an empirical FDM−2 dependence, while NM-led damping times remain within $0.12−−0.33\,\mathrm{s}$. Halo DM-led damping instead increases with dark fraction: at the same stellar mass and FDM=20%, dark radii approach 88 km, frequencies fall to 0.14 kHz, and damping times reach approximately 450 s. Selected high-mass core sequences exhibit strong DM-led damping-time upturns not reproduced by the leading mass-quadrupole diagnostic. Representative core calculations show greater DM-led sensitivity to the bosonic self-coupling and retain both branches at ℓ=3. Under the adopted nonrotating, circular-binary prescriptions, no evaluated configuration satisfies all geometric and perturbative conditions for a controlled linear tidal resonance.
Related
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BibTeX
@misc{thakur2026dark,
title = {{Dark matter in neutron stars: two-fluid $f$-mode oscillations in full general relativity}},
author = {Prashant Thakur and Ishfaq Ahmad Rather and Y. Lim},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.04282},
eprint = {2610.04282},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.04282},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Dark matter in neutron stars: two-fluid f-mode oscillations in full general relativity
AU - Prashant Thakur
AU - Ishfaq Ahmad Rather
AU - Y. Lim
PY - 2026
DA - 2026/10/03
PB - arXiv
DO - 10.48550/arxiv.2610.04282
UR - https://arxiv.org/abs/2610.04282
AB - A dark-matter core and a soft nuclear equation of state can produce similar mass--radius signatures, motivating a complementary probe through the f-mode spectrum. We compute quadrupolar f-mode frequencies and gravitational-wave damping times in full general relativity for cold, nonrotating neutron stars admixed with self-interacting bosonic dark matter (DM). Our two-fluid survey spans 21 nuclear equations of state covering nucleonic, hyperonic, Δ-admixed, and combined hyperon--Δ compositions at F_DM=1--20%. The main sequences use λ=π and boson masses of $500$ and 100 MeV for the core and halo studies, respectively. Independent normal-matter (NM) and DM displacements couple through the metric, yielding NM-led and DM-led f-mode branches whose radiative damping is determined by outgoing-wave boundary conditions. At 1.4 M_⊙, the core DM-led damping time decreases from order 10^3 s at F_DM=1% to order 1 s at 20%, approximately following an empirical F_DM^−2 dependence, while NM-led damping times remain within $0.12−−0.33\,\mathrm{s}$. Halo DM-led damping instead increases with dark fraction: at the same stellar mass and F_DM=20%, dark radii approach 88 km, frequencies fall to 0.14 kHz, and damping times reach approximately 450 s. Selected high-mass core sequences exhibit strong DM-led damping-time upturns not reproduced by the leading mass-quadrupole diagnostic. Representative core calculations show greater DM-led sensitivity to the bosonic self-coupling and retain both branches at ℓ=3. Under the adopted nonrotating, circular-binary prescriptions, no evaluated configuration satisfies all geometric and perturbative conditions for a controlled linear tidal resonance.
ER -