PBH-infused seesaw origin of matter and unique gravitational waves

TL;DR

This paper proposes a model where primordial black holes produce super-heavy right-handed neutrino dark matter and baryon asymmetry, with unique gravitational wave signatures from PBH fluctuations and cosmic strings, testable by GW detectors.

Contribution

It introduces a novel scenario linking primordial black holes, super-heavy neutrinos, and gravitational waves, providing testable predictions for high-scale physics.

Findings

Primordial black holes can produce super-heavy neutrino dark matter via Hawking radiation.

Gravitational wave spectra from PBH fluctuations and cosmic strings are detectable by current and future GW observatories.

Distinct GW signatures correlate with dark matter and baryogenesis processes in the early universe.

Abstract

The Standard Model, extended with three right-handed (RH) neutrinos, is the simplest model that can explain light neutrino masses, the baryon asymmetry of the Universe, and dark matter (DM). Models in which RH neutrinos are light are generally easier to test in experiments. In this work, we show that, even if the RH neutrinos are super-heavy ($M_{i=1,2,3}>10^9$ GeV) -- close to the Grand Unification scale -- the model can be tested thanks to its distinct features on the stochastic Gravitational Wave (GW) background. We consider an early Universe filled with ultralight primordial black holes (PBH) that produce a super-heavy RH neutrino DM via Hawking radiation. The other pair of RH neutrinos generates the baryon asymmetry via thermal leptogenesis, much before the PBHs evaporate. GW interferometers can test this novel spectrum of masses thanks to the GWs induced by the PBH density fluctuations. In a more refined version, wherein a $U(1)$ gauge symmetry breaking dynamically generates the seesaw scale, the PBHs also cause observable spectral distortions on the GWs from the $U(1)$-breaking cosmic strings. Thence, a low-frequency GW feature related to DM genesis and detectable with a pulsar-timing array must correspond to a mid- or high-frequency GW signature related to baryogenesis at interferometer scales.