{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/comprehensive-constraints-on-dark-radiation","title":"Comprehensive Constraints on Dark Radiation Injection After BBN","arxiv_id":"2312.13235","date":"2023-12-20","proceeding":null,"authors":["Alexander C. Sobotka","Adrienne L. Erickcek","Tristan L. Smith"],"abstract":"We derive constraints on the injection of free-streaming dark radiation after big bang nucleosynthesis (BBN) by considering the decay of a massive hidden sector particle into dark radiation. Such a scenario has the potential to alleviate the Hubble tension by introducing a new energy component to the evolution of the early universe. We employ observations of the cosmic microwave background (CMB) from $\\textit{Planck}$ 2018 and the South Pole Telescope (SPT-3G), measurements of the primordial deuterium abundance, Pantheon+ Type Ia supernovae data, and baryon acoustic oscillation (BAO) measurements from BOSS DR12 to constrain these decay scenarios. Pre-recombination decays are primarily restricted by observations of the CMB via their impact on the effective number of relativistic species. On the other hand, long-lived decay scenarios in which the massive particle lifetime extends past recombination tend to decrease the late-time matter density inferred from the CMB and are thus subject to constraints from Pantheon+ and BAO. We find that, when marginalizing over lifetimes of $\\tau_Y = [10^{-12.08}, 10^{-1.49}]$ Gyr, the decaying particle is limited at $2\\sigma$ to only contribute a maximum of $3\\%$ of the energy density of the universe. With limits on these decays being so stringent, neither short-lived nor long-lived scenarios are successful at substantially mitigating the Hubble tension.","url_abs":"https://arxiv.org/abs/2312.13235v2","url_pdf":"https://arxiv.org/pdf/2312.13235v2.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"comprehensive-constraints-on-dark-radiation","repo_url":"https://github.com/alexsobotka/class_ytodr","is_official":1,"mentioned_in_paper":1,"mentioned_in_github":1,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}