Gravitational Waves from Primordial Black Holes and New Weak Scale Phenomena

TL;DR

This paper explores the potential for detecting gravitational waves from primordial black holes that could make up a significant portion of dark matter, originating from early universe phase transitions, with implications for current and future gravitational wave observatories.

Contribution

It proposes a novel scenario where small primordial black holes form binaries with neutron stars or black holes, producing detectable gravitational waves and linking dark matter, phase transitions, and gravitational wave astronomy.

Findings

Primordial black holes of mass 10^{26}-10^{29} g could constitute over 10% of dark matter.

Gravitational waves from black hole-neutron star binaries may be detectable within 10 Mpc.

Detection could be corroborated by new particle discoveries and signals from early universe phase transitions.

Abstract

We entertain the possibility that primordialblack holes of mass $\sim (10^{26}$--$10^{29})$~g, with Schwarzschild radii of $\mathcal{O}{\text{cm}}$, constitute $\sim 10\%$ or more of cosmic dark matter, as allowed by various constraints. These black holes would typically originate from cosmological eras corresponding to temperatures $\mathcal{O}{10-100}$~GeV, and may be associated with first order phase transitions in the visible or hidden sectors. In case these small primordial black holes get captured in orbits around neutron stars or astrophysical black holes in our galactic neighborhood, gravitational waves from the resulting "David and Goliath (D\&G)" binaries could be detectable at Advanced LIGO or Advanced Virgo for hours or more, possibly over distances of $\mathcal{O}{10}$~Mpc encompassing the Local Supercluster of galaxies. The proposed Einstein Telescope would further expand the reach for these signals. A positive signal could be further corroborated by the discovery of new particles in the $\mathcal{O}{10-100}$~GeV mass range, and potentially also the detection of long wavelength gravitational waves originating from the first order phase transition era.