Pre-inflationary QCD axion stars after moduli domination

Journal article

The growth of adiabatic density perturbations during an era of early matter domination induces O(1) fluctuations in pre-inflationary QCD axion dark matter across a broad, string-theory-motivated parameter space. Remarkably, at ΛCDM matter-radiation equality the scale of these perturbations coincides with the quantum Jeans scale, so they collapse to solitonic “axion stars”. These axion stars have densities up to 10⁴ eV⁴ , and, including their surrounding halos, they contain as much as 50% of dark matter. Direct searches for a smooth axion background can be suppressed, but transient enhancements or indirect astrophysical signals at axion masses m_a ≲ 10⁻⁵ eV would point to a non-standard cosmological history.

Authors: Hardy, E; Sánchez González, N; Stubbs, H; Tranchedone, L

• Publication status: Accepted
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review D: Particles, Fields, Gravitation and Cosmology
• Acceptance date: 2026-06-02
• DOI: 10.1103/23zs-8wmn
• EISSN: 1550-2368
• ISSN: 1550-7998
• Language: English