2022/04/03 by Howard Baer, Vernon Barger, Baer, Howard +4
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #Particle physics theoretical and experimental studies #astro-ph.CO #hep-ph
paper · pdf · doi:10.48550/arxiv.2204.01130
18 pages with 9 .png figures
arxiv created 2022/04/03 · openalex publication_date 2022/04/03 · arxiv updated 2022/04/05 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We examine the issue of dark radiation (DR) from string moduli decay into axion-like particles (ALPs). In KKLT-type models of moduli stabilization, the axionlike phases of moduli fields are expected to decouple whilst in LVS-type moduli stabilization some can remain light and may constitute dark radiation. We evaluate modulus decay to Minimal Supersymmetric Standard Model (MSSM) particles and dark radiation for more general compactifications. In spite of tightening error bars on ΔNeff, we find only mild constraints on modulus-ALP couplings due to the somewhat suppressed modulus branching fraction to DR owing to the large number of MSSM decay modes. We anticipate that future CMB experiments with greater precision on ΔNeff may still turn up evidence for DR if the ALP associated with the lightest modulus field is indeed light.