{"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/crrfast-an-emulator-for-the-cosmological","title":"CRRfast: An emulator for the Cosmological Recombination Radiation with effects from inhomogeneous recombination","arxiv_id":"2306.08085","date":"2023-06-13","proceeding":null,"authors":["Matteo Lucca","Jens Chluba","Aditya Rotti"],"abstract":"The Cosmological Recombination Radiation (CRR) is one of the guaranteed $\\Lambda$CDM Spectral Distortion (SD) signals. Even if very small in amplitude, it provides a direct probe of the three recombination eras, opening the path for testing one of the key pillars in our cosmological interpretation of the measured CMB anisotropies. Here we develop a new emulator, CRRfast, to quickly and accurately represent the CRR for a wide range of cosmologies, using the state-of-the-art CosmoSpec code as a reference. CRRfast has been made publicly available both as stand-alone code and as part of CLASS, thereby completing the set of $\\Lambda$CDM sources of SDs that can be modeled with CLASS. With this newly-developed pipeline we investigate the full constraining power of SDs within $\\Lambda$CDM and highlight possible future applications to experimental design optimization. Furthermore, we show that the inhomogeneous evolution of the recombination process imprints second-order contributions to the CRR spectrum, leading to a broadening and shifting of the CRR features. These second-order terms are naturally captured by the emulator and allow us to evaluate the $\\Lambda$CDM contributions to the average CRR as well as to illustrate the effect of perturbed recombination due to Primordial Magnetic Fields (PMFs). As it turns out, while the $\\Lambda$CDM variance effects can be neglected, they could be significantly enhanced in the beyond-$\\Lambda$CDM models. In particular in the case of PMFs we demonstrate that through these non-linear terms the parameter space relevant to the Hubble tension could be tested with future CMB spectrometers.","url_abs":"https://arxiv.org/abs/2306.08085v1","url_pdf":"https://arxiv.org/pdf/2306.08085v1.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":"crrfast-an-emulator-for-the-cosmological","repo_url":"https://github.com/luccamatteo/crrfast","is_official":1,"mentioned_in_paper":1,"mentioned_in_github":1,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"syntology_url":null,"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}