2023/12/13 by Vadim Briaud, Briaud, Vadim, Kenji Kadota +7
Physics and Astronomy · #Cosmology and Gravitation Theories #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 · doi:10.48550/arxiv.2312.08231
openalex publication_date 2023/12/13 · openalex created_date 2023/12/15 · openalex updated_date 2026/07/28
If dark matter is made of QCD axions, its abundance is determined by the vacuum expectation value acquired by the axion field during inflation. The axion is usually assumed to follow the equilibrium distribution arising from quantum diffusion during inflation. This leads to the so-called stochastic window under which the QCD axion can make up all the dark matter. It is characterised by 1010.4GeV≤ f≤ 1017.2GeV and Hend>10-2.2GeV, where f is the axion decay constant and Hend is the Hubble expansion rate at the end of inflation. However, in realistic inflationary potentials, we show that the axion never reaches the equilibrium distribution at the end of inflation. This is because the relaxation time of the axion is much larger than the typical time scale over which H varies during inflation. As a consequence, the axion acquires a quasi-flat distribution as long as it remains light during inflation. This leads us to reassessing the stochastic axion window, and we find that 1010.3GeV≤ f≤ 1014.1GeV and Hend>10-13.8GeV.