Abstract
We consider gravitationally bound states of asymmetric dark matter (ADM stars), and the impact of ADM capture on the stability of neutron stars. We derive and interpret the equation of state for ADM with both attractive and repulsive interactions, and solve the Tolman-Oppenheimer-Volkoff equations to find equilibrium sequences and maximum masses of ADM stars. Gravitational wave searches can utilize our solutions to model exotic compact objects (ECOs). Our results for attractive interactions differ substantially from those in the literature, where fermionic ADM with attractive self-interactions was employed to destabilize neutron stars more effectively than non-interacting fermionic ADM. By contrast, we argue that fermionic ADM with an attractive force is no more effective in destabilizing neutron stars than fermionic ADM with no self-interactions.
Highlights
Work on hidden sector dark matter has exploded over the last decade [1]
We have argued that the capture of spin-1=2 asymmetric dark matter (ADM) by neutron stars cannot lead to their implosion unless the mass of the spin-1=2 ADM constituents exceeds approximately 1 PeV
If there is a positive detection of dark kinetic heating of NSs, the existence of old neutron stars will provide complementary information on possible models of ADM with mX ≳ PeV
Summary
Work on hidden sector dark matter has exploded over the last decade [1]. One conclusion of this work is that even modest extensions of the standard paradigm of dark matter—as a single, stable, weakly interacting particle coupling only via Standard Model forces—to include the dynamics of dark forces can change the cosmology, astrophysics, and terrestrial signatures of the dark sector [2]. For C2φ > 1.09 there is a global minimum in ε=n, with energy per constituent at this minimum less than mX (the value at n 1⁄4 0), indicating the existence of large stable bound states, or nuggets, that form without the aid of gravity through a fusion process Shown by the dashed red line, as, the EoS has an intermediate regime below the saturation density where the ADM fuses; once fusion has completed and the star has cooled again, saturation is reached and the pressure turns positive again, indicating the possibility for a stable equilibrium between gravitational forces, binding forces, and Fermi degeneracy pressure. With the EoS for ADM self-interacting through scalar and vector exchange in hand, we explore the structure of self-gravitating objects composed of such matter
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