Inflationary theory and pulsar timing investigations of primordial black holes and gravitational waves

Abstract

The gravitational waves measured at LIGO are presumed here to come from merging primordial black holes. We ask how these primordial black holes could arise through inflationary models while not conflicting with current experiments. Among the approaches that work, we investigate the opportunity for corroboration through experimental probes of gravitational waves at pulsar timing arrays. We provide examples of theories that are already ruled out, theories that will soon be probed, and theories that will not be tested in the foreseeable future. The models that are most strongly constrained are those with a relatively broad primordial power spectrum.

Pulsar timing probes of primordial black holes and subhalos

“…They arise in many theories with inflationary dynamics producing large density perturbations on small scales, e.g. [18][19][20][21][22]. They are one extreme of the generic density profile and hence serve as a benchmark for gravitational probes of small scale structure.…”

Gauge independence of induced gravitational waves

“…Gravitational waves (GWs) are a useful probe of small-scale curvature perturbations [3][4][5][6][7][8] since if the latter is enhanced, a sizable amount of GWs is produced at the second order of the cosmological perturbation. We call it the induced GWs 1 (see early works [9][10][11][12] and recent developments [13][14][15][16][17][18][19][20][21][22]).…”

Gravitational waves from double-inflection-point inflation

“…Therefore, the induced GWs are used to constrain on the abundance of primordial black holes and vice versa [21][22][23][24][25][26].…”