Primordial black holes and gravitational waves from aligned axion inflation

Nadir Ijaz

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arXiv · 2610.41823

Primordial black holes and gravitational waves from aligned axion inflation

Nadir Ijaz

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Abstract

We study the production of primordial black holes (PBHs) and scalar-induced gravitational waves (SIGWs) in aligned axion inflation through the transition between two stages of inflation. The first stage proceeds along a metastable trajectory and ends when this trajectory loses stability, causing the fields to turn towards the attractor of the second inflationary stage. During the transition, coupled adiabatic--entropy evolution produces a localized enhancement of the curvature power spectrum. We compute the PBH abundance from this spectrum assuming Gaussian primordial curvature perturbations and using the nonlinear compaction-function formalism with a spectrum-dependent collapse threshold and critical collapse. Representative benchmark solutions yield asteroid-mass PBHs with a potentially significant dark-matter abundance, together with an associated SIGW background.

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Nadir Ijaz. 2026-10-30. Primordial black holes and gravitational waves from aligned axion inflation. https://arxiv.org/abs/2610.41823

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