Effect of neutron dark decay under neutron star interior conditions

Determine how the neutron dark decay channel n → χ + φ is affected by the extreme physical conditions inside neutron star cores, including high densities, pressures, temperatures, and intense fields, and ascertain the extent of any modification to the decay under these conditions.

Background

The paper investigates how nuclear symmetry energy influences equations of state for β-stable matter that includes dark sector components produced by neutron dark decay, considering both dark matter self-interactions and dark matter–baryon interactions. The authors emphasize that most prior studies focused on pure neutron matter, while this work incorporates β-stable nuclear matter and interaction effects.

They note that laboratory studies of neutron dark decay do not reflect the extreme environment of neutron stars, where conditions could significantly alter the feasibility of the decay. The authors explicitly state that the extent to which neutron dark decay is modified in neutron star interiors is currently unresolved, motivating further investigation.

References

In any case, the extent to which the proposed dark decay of the neutron is affected by the extreme conditions prevailing in the interior of neutron stars remains an open problem.

— Neutron Dark Decay in Neutron Stars: The Role of the Symmetry Energy  (2508.21754 - Divaris et al., 29 Aug 2025) in Abstract

A microscopic evaluation of the in-medium conversion rate requires a specific reaction channel and the corresponding many-body matrix element. Since the present work is concerned with the equilibrium EOS, we do not attempt such a rate calculation. We assume that the nonzero neutron-dark-baryon mixing is sufficient to establish chemical equilibrium over the stellar lifetime. The equilibrium composition is then independent of the magnitude of $g_c$, provided that the equilibration timescale remains shorter than the age of the star. A quantitative calculation of the conversion timescale is left for future work.

— Density-induced dark-baryon conversion in $Δ-$admixed hypernuclear neutron stars  (2608.17409 - Kalita et al., 18 Aug 2026) in Appendix A: Higgs-portal sector and numerical estimate