Primordial black hole dark matter from axion inflation
Gabriele Franciolini, Nadir Ijaz, Marco Peloso
TLDR
This paper explores how primordial black holes from axion inflation can explain all dark matter and generate detectable gravitational waves.
Key contributions
- Revisits primordial black hole (PBH) production from axion inflation via a U(1) gauge field.
- Improves PBH abundance calculations using homogeneous backreaction and numerical gauge mode functions.
- Shows PBHs can account for all dark matter in the asteroidal mass range.
- Predicts a stochastic gravitational wave background detectable by LISA, aiding in discriminating δρ statistics.
Why it matters
This research offers a compelling mechanism for primordial black holes to explain dark matter, addressing a major cosmic mystery. It also predicts a testable gravitational wave signature, providing a way to validate the model and distinguish between different statistical properties of density fluctuations.
Original Abstract
We revisit the production of primordial black holes (PBHs) by a U(1) gauge field with a pseudo-scalar coupling to the inflaton. We improve upon the existing literature by working in the homogeneous backreaction regime with numerically computed gauge mode functions, adopting state-of-the-art PBH abundance calculations, and incorporating the uncertainty in the statistics of $δρ$. We find that PBHs can account for all of the dark matter in the asteroidal mass range, even when the inflaton gradient energy density is highly subdominant ($10^{-4}$--$10^{-3}$ of the kinetic energy), supporting the validity of the backreaction scheme. This mechanism also unavoidably generates a stochastic gravitational wave background with an amplitude that will be measured at LISA and that will allow to indirectly discriminate between different statistics of $δρ$.
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