2025/05/07 by Andrew Cheek, Anish Ghoshal, Cheek, Andrew +3
Computer Science · Physics and Astronomy · #Computational Physics and Python Applications #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #Particle physics theoretical and experimental studies
paper · pdf · doi:10.48550/arxiv.2505.04614
openalex publication_date 2025/05/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
We investigate the complementary information to be gained from inflationary gravitational wave (IGW) signals and searches for QCD axion dark matter. We focus on post-inflationary Peccei-Quinn (PQ) breaking axion models that are cosmologically safe. Recent work has shown that a greater number of such models exist. This is because the heavy quarks required for the colour anomaly can provoke a period of heavy quark domination (HQD), which, through decay, dilutes the axion abundance. In this work we show for the first time that the axion dark matter mass can be as low as ma∼10-8 \rm eV for models where the heavy quarks decay via dimension 6 terms. This is achieved by allowing the mass of the heavy quarks to differ from the axion decay constant, mQ≠ fa. Consequently, the observables that would distinguish between pre- and post-inflationary PQ breaking, ma and the additional relativistic degrees of freedom ΔN\rm eff, now become indiscernible. To solve this, we propose using blue-tilted IGWs to probe HQD. In scenarios where such a blue tilt is present, the enhanced GW signal allows future interferometers to place non-trivial constraints on the parameters mQ and fa, thereby complementing haloscope searches. While some degeneracies with other parameters such as mQ remain, detectors such as BBO and ET will be able to optimistically probe fa\gtrsim 1014 \rm GeV.