Compact Stars as Portals to Extra-Dimensional Dark Matter

TL;DR

This paper explores how extra-dimensional propagation of dark matter affects neutron star stability, leading to potential black hole formation and new constraints on dark matter properties.

Contribution

It introduces a model where fermionic dark matter propagates into extra dimensions, affecting neutron star collapse and setting novel limits on dark matter mass and extra-dimensional size.

Findings

Dark matter in extra dimensions can cause neutron stars to collapse into black holes.

Constraints on dark matter mass are significantly lower in extra-dimensional scenarios.

Longer-lived black holes from extra-dimensional collapse can consume entire neutron stars.

Abstract

We investigate hydrostatic configurations of asymmetric dark matter (DM) spheres in scenarios where fermionic DM can propagate into extra spatial dimensions, while Standard Model fields remain confined to ordinary three dimensions. As the number of extra dimensions increases, the effective equation of state for non-relativistic matter softens, making even modest DM accumulation inside neutron stars susceptible to gravitational collapse into extra-dimensional black holes. These black holes are longer lived than their $3$ dimensional counterparts and can accrete enough material to consume an entire neutron star, ultimately producing solar-mass black holes. For geometric cross sections, DM with masses above $\mathcal{O}(10\,{\rm TeV})$ may already be excluded for more than two extra dimensions of size ${\mathcal{O}(\rm fm})$ -- sharply contrasting with the standard $3$ dimensional case, where comparable limits only appear for masses $\gtrsim 10^{5}$ TeV at typical halo densities of $0.3\, \rm{GeV/cm^3}$.