2016/07/31 by Anupam Mazumdar, Saleh Qutub, Ken'ichi Saikawa +1
Physics and Astronomy · #Astrophysics #Axion #Cosmic microwave background #Cosmology #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark energy #Dark matter #Dark radiation #Hot dark matter #Inflation (cosmology) #Light dark matter #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum mechanics #Radiation #Scalar field dark matter #Theoretical physics #Universe #astro-ph.CO #astro-ph.HE #hep-ph #hep-th
paper · pdf · doi:10.1103/physrevd.94.065030
published as Phys. Rev. D 94, 065030 (2016) · 12 pages, 2 figures; v2: typos corrected, text modified, to appear in PRD
arxiv created 2016/09/10 · openalex publication_date 2016/09/22 · arxiv updated 2016/09/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The Peccei-Quinn mechanism presents a neat solution to the strong CP problem. As a by-product, it provides an ideal dark matter candidate, ``the axion'', albeit with a tiny mass. Axions therefore can act as dark radiation if excited with large momenta after the end of inflation. Nevertheless, the recent measurement of relativistic degrees of freedom from cosmic microwave background radiation strictly constrains the abundance of such extra relativistic species. We show that ultrarelativistic axions can be abundantly produced if the Peccei-Quinn field was initially displaced from the minimum of the potential. This in lieu places an interesting constraint on the axion dark matter window with large decay constant which is expected to be probed by future experiments. Moreover, an upper bound on the reheating temperature can be placed, which further constrains the thermal history of our Universe.