Trace-anomaly decomposition and universal dark matter scaling in compact stars
Abstract
We investigate how dark matter (DM) admixture modifies the conformal properties and phase structure of dense neutron-star matter within a self-consistent single-fluid framework, with the global DM fraction Fχ=Nχ/NB fixing the local relation nχ=FχnB. We derive an exact decomposition of the total trace anomaly, Δtot, into microscopic contributions. For collider-motivated Higgs-portal benchmarks, explicit Higgs, vector-mediator, and contact-interaction contributions are negligible, while heavy nonrelativistic DM has an intrinsic trace anomaly close to the nonrelativistic limit, Δχ≃1/3. Consequently, the DM rest-mass energy fraction dominates the DM-induced modification of Δtot, producing a smooth upward shift of up to ∼0.1 for Fχ∼0.2%. In the pressureless, comoving heavy-WIMP regime, we further identify a universal dark-sector scaling governed by the mass-loading parameter λ=Fχmχ/mN: numerical calculations with different (Fχ,mχ) pairs at fixed λ exhibit overlapping trace-anomaly, sound-speed, and mass--radius responses for a given baryonic equation of state. In hybrid stars, DM leaves the coexistence pressure and chemical potential essentially unchanged, whereas first-order hadron--quark deconfinement produces sharp discontinuities in the squared sound speed cs2, Δtot, and Δtot−ΔB. The combined softening substantially reduces the maximum stellar mass, placing Fχ∼0.2% in tension with the observed 2 M⊙ neutron stars. These results show that the trace anomaly and its density evolution provide a sensitive diagnostic for distinguishing smooth DM-induced modifications of dense matter from genuine first-order deconfinement.
Related
- Unified Scaling Relation for Coronal Temperature Anomaly and Solar Wind Acceleration
- Universal Z2/3/√(Qα) Scaling Law in Alpha Decay from Nuclei to Neutron-Star Mergers
- Two-Fluid Radial Stability of Dark-Matter-Admixed Compact Objects: Dark Compact Planets, Dark White Dwarfs, Dark Neutron Stars, and Dark Oysters
- Reconstructing the Dark Matter Equation of State with Compact Object Inspirals
- Compact Dark Matter with Globular Cluster Pulsars
BibTeX
@misc{issifu2026traceanomaly,
title = {{Trace-anomaly decomposition and universal dark matter scaling in compact stars}},
author = {Adamu Issifu and Constança Providência and Tobias Frederico},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.01991},
eprint = {2610.01991},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.01991},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Trace-anomaly decomposition and universal dark matter scaling in compact stars
AU - Adamu Issifu
AU - Constança Providência
AU - Tobias Frederico
PY - 2026
DA - 2026/10/01
PB - arXiv
DO - 10.48550/arxiv.2610.01991
UR - https://arxiv.org/abs/2610.01991
AB - We investigate how dark matter (DM) admixture modifies the conformal properties and phase structure of dense neutron-star matter within a self-consistent single-fluid framework, with the global DM fraction F_χ=N_χ/N_B fixing the local relation n_χ=F_χn_B. We derive an exact decomposition of the total trace anomaly, Δ_tot, into microscopic contributions. For collider-motivated Higgs-portal benchmarks, explicit Higgs, vector-mediator, and contact-interaction contributions are negligible, while heavy nonrelativistic DM has an intrinsic trace anomaly close to the nonrelativistic limit, Δ_χ≃1/3. Consequently, the DM rest-mass energy fraction dominates the DM-induced modification of Δ_tot, producing a smooth upward shift of up to ∼0.1 for F_χ∼0.2%. In the pressureless, comoving heavy-WIMP regime, we further identify a universal dark-sector scaling governed by the mass-loading parameter λ=F_χm_χ/m_N: numerical calculations with different (F_χ,m_χ) pairs at fixed λ exhibit overlapping trace-anomaly, sound-speed, and mass--radius responses for a given baryonic equation of state. In hybrid stars, DM leaves the coexistence pressure and chemical potential essentially unchanged, whereas first-order hadron--quark deconfinement produces sharp discontinuities in the squared sound speed c_s^2, Δ_tot, and Δ_tot−Δ_B. The combined softening substantially reduces the maximum stellar mass, placing F_χ∼0.2% in tension with the observed 2 M_⊙ neutron stars. These results show that the trace anomaly and its density evolution provide a sensitive diagnostic for distinguishing smooth DM-induced modifications of dense matter from genuine first-order deconfinement.
ER -