Astrophage of neutron stars from supersymmetric dark matter Q-balls

TL;DR

This paper explores how supersymmetric Q-balls, as dark matter candidates, can destabilize neutron stars upon absorption, leading to new constraints on Q-ball properties and gravitino mass.

Contribution

It introduces the effects of gravity-mediation on Q-balls, showing their growth, fragmentation, and potential to destroy neutron stars, thus setting new limits on Q-ball dark matter.

Findings

Q-balls grow until a size limit set by gravity-mediation

Absorbing a single Q-ball can destroy a neutron star

Ultralight gravitino mass (< keV) is required for Q-ball dark matter

Abstract

The gauge-mediated model of supersymmetry breaking implies that stable non-topological solitons, Q-balls, could form in the early universe and comprise the dark matter. It is shown that the inclusion of the effects from gravity-mediation set an upper limit on the size of Q-balls. When in a dense baryonic environment Q-balls grow until reaching this limiting size at which point they fragment into two equal-sized Q-balls. This Q-splitting process will rapidly destroy a neutron star that absorbs even one Q-ball. The new limits on Q-ball dark matter require an ultralight gravitino m_3/2 < keV, naturally avoiding the gravitino overclosure problem, and providing the MSSM with a dark matter candidate where gravitino dark matter is not viable.