2024/03/20 by Emanuela Dimastrogiovanni, Matteo Fasiello, Dimastrogiovanni, Ema +3
Earth and Planetary Sciences · Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Geophysics and Gravity Measurements #High Energy Physics - Phenomenology (hep-ph) #Solar and Space Plasma Dynamics
paper · pdf · doi:10.48550/arxiv.2403.13581
openalex publication_date 2024/03/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We consider the case of axion-like particles (ALPs) during inflation. When coupled to a non-Abelian gauge sector via a Chern-Simons term, ALPs support an intriguing, testable, phenomenology with very distinctive features including chiral primordial gravitational waves. For sufficiently small values of the gauge vev and coupling, scalar perturbations in the gauge sector exhibit a known instability. We harness the power of such instability for primordial black hole (PBH) generation. In the case of an axion-inflaton, one is dynamically driven into a strong-backreaction regime that crosses the instability band thereby sourcing a peaked scalar spectrum leading to PBH production and the related scalar-induced gravitational waves. Remarkably, this dynamics is largely insensitive to the initial conditions and the shape of the potential, highlighting the universal nature of the sourcing mechanism. In the case of spectator ALPs one can identify the parameter space that sets off the strong backreaction regime and the ensuing features. We show that spectator ALP models may also access the scalar instability region without triggering strong backreaction.