Two-Fluid Radial Stability of Dark-Matter-Admixed Compact Objects: Dark Compact Planets, Dark White Dwarfs, Dark Neutron Stars, and Dark Oysters
Abstract
We investigate the equilibrium structure and stability against radial oscillations of a variety of two-fluid compact objects containing ordinary baryonic matter admixed with cold dark matter coupled through the background spacetime. For the ordinary fluid, we employ a QCD equation of state compatible with chiral effective field theory at nuclear densities (supplemented by the BPS and Negele-Vautherin models at extremely low densities) and with perturbative QCD in the high-density regime while also satisfying also current astrophysical data. For the dark fluid, we assume self-interacting fermionic matter with particle masses of mf= 2, 5, 10, and 100 GeV and two self-interaction strengths of y=0.1 and 103. By scanning a large range of central pressures for both fluids, we identify the presence of dark compact planets, dark white dwarfs, dark neutron stars and the so-called dark oysters. Importantly, these objects are not only in two-fluid hydrostatic equilibrium, but they are also stable against two-fluid radial oscillations. We find that the relative representation of each class in the radially stable sample is strongly sensitive to the combinations of mf and y, with some combinations entirely suppressing some of these object classes within the sampled domain while favoring others. In addition to these classes, strong self-repulsion supports stable, dark-matter-dominated branches with compact ordinary-matter cores and extended dark halos, approaching the self-interacting fermion-star limit. Finally, we calculate the gravitational redshift at the ordinary-matter surface, zOM, including the contribution of extended dark-matter halos for which we found radially stable configurations with zOM>2.
Related
- The kinematic Kelvin-Helmholtz instability-driven dynamo: implications for merging compact objects
- Characterization of the Compact Multi-planet System TOI-789: Validation of Three Terrestrial Planets, Dynamical Characterization, and Detection of a Fourth Temperate Candidate
- Characterization of the Compact Multiplanet System TOI-789: Validation of Three Terrestrial Planets, Dynamical Characterization, and Detection of a Fourth Temperate Candidate
- Impact of the Host Galaxy on the Search for Gravitational-Wave Microlensing by Compact Objects
- The macroscopic precession model of quasiperiodic oscillations for rotating compact objects
BibTeX
@misc{jimenez2026twofluid,
title = {{Two-Fluid Radial Stability of Dark-Matter-Admixed Compact Objects: Dark Compact Planets, Dark White Dwarfs, Dark Neutron Stars, and Dark Oysters}},
author = {José C. Jiménez and Oscar Pastor and Laura Tolos},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.41082},
eprint = {2610.41082},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.41082},
}
RIS
TY - UNPB
TI - Two-Fluid Radial Stability of Dark-Matter-Admixed Compact Objects: Dark Compact Planets, Dark White Dwarfs, Dark Neutron Stars, and Dark Oysters
AU - José C. Jiménez
AU - Oscar Pastor
AU - Laura Tolos
PY - 2026
DA - 2026/10/29
PB - arXiv
DO - 10.48550/arxiv.2610.41082
UR - https://arxiv.org/abs/2610.41082
AB - We investigate the equilibrium structure and stability against radial oscillations of a variety of two-fluid compact objects containing ordinary baryonic matter admixed with cold dark matter coupled through the background spacetime. For the ordinary fluid, we employ a QCD equation of state compatible with chiral effective field theory at nuclear densities (supplemented by the BPS and Negele-Vautherin models at extremely low densities) and with perturbative QCD in the high-density regime while also satisfying also current astrophysical data. For the dark fluid, we assume self-interacting fermionic matter with particle masses of m_f= 2, 5, 10, and 100 GeV and two self-interaction strengths of y=0.1 and 10^3. By scanning a large range of central pressures for both fluids, we identify the presence of dark compact planets, dark white dwarfs, dark neutron stars and the so-called dark oysters. Importantly, these objects are not only in two-fluid hydrostatic equilibrium, but they are also stable against two-fluid radial oscillations. We find that the relative representation of each class in the radially stable sample is strongly sensitive to the combinations of m_f and y, with some combinations entirely suppressing some of these object classes within the sampled domain while favoring others. In addition to these classes, strong self-repulsion supports stable, dark-matter-dominated branches with compact ordinary-matter cores and extended dark halos, approaching the self-interacting fermion-star limit. Finally, we calculate the gravitational redshift at the ordinary-matter surface, z_OM, including the contribution of extended dark-matter halos for which we found radially stable configurations with z_OM>2.
ER -