2014/01/31 by Kfir Blum, Raffaele Tito D’Agnolo, Raffaele Tito D'Agnolo +2
Physics and Astronomy · #Astrophysics #Axion #Big Bang nucleosynthesis #Cosmology #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark matter #Neutron #Nuclear physics #Nucleosynthesis #Parameter space #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum chromodynamics #Supernova #Universe #astro-ph.CO #hep-ph
paper · pdf · doi:10.1016/j.physletb.2014.07.059
5 pages, 2 figures; v2 typos corrected, numerical values for quark masses updated
arxiv created 2014/02/05 · openalex publication_date 2014/08/04 · arxiv updated 2015/06/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We show that Big Bang Nucleosynthesis (BBN) significantly constrains axion-like dark matter. The axion acts like an oscillating QCD θ angle that redshifts in the early Universe, increasing the neutron–proton mass difference at neutron freeze-out. An axion-like particle that couples too strongly to QCD results in the underproduction of He4 during BBN and is thus excluded. The BBN bound overlaps with much of the parameter space that would be covered by proposed searches for a time-varying neutron EDM. The QCD axion does not couple strongly enough to affect BBN.