{"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/cmb-s4-iterative-internal-delensing-and-r","title":"CMB-S4: Iterative Internal Delensing and $r$ Constraints","arxiv_id":"2310.06729","date":"2023-10-10","proceeding":null,"authors":["Sebastian Belkner","Julien Carron","Louis Legrand","Caterina Umiltà","Clem Pryke","Colin Bischoff"],"abstract":"The tightest constraints on the tensor-to-scalar ratio $r$ can only be obtained after removing a substantial fraction of the lensing $B$-mode sample variance. The planned CMB-S4 experiment will remove the lensing $B$-mode signal internally by reconstructing the gravitational lenses from high-resolution observations. We document here a first lensing reconstruction pipeline able to achieve this optimally for arbitrary sky coverage. We make it part of a map-based framework to test CMB-S4 delensing performance and its constraining power on $r$, including inhomogeneous noise and two non-Gaussian Galactic polarized foreground models. The framework performs component-separation of the high-resolution maps, followed by the construction of lensing $B$-mode templates, which are then included in a parametric small-aperture maps cross-spectra-based likelihood for $r$. We find that the lensing reconstruction and framework achieve the expected performance, compatible with the target $\\sigma(r) \\simeq 5\\cdot 10^{-4}$ in the absence of a tensor signal, after an effective removal of $92\\%$ to $93\\%$ of the lensing $B$-mode variance, depending on the simulation set. The code for the lensing reconstruction can also be used for cross-correlation studies with large-scale structures, lensing spectrum reconstruction, cluster lensing, or other CMB lensing-related purposes. As part of our tests we also demonstrate joint optimal reconstruction of the lensing potential with the lensing curl potential mode, second-order in the density fluctuations.","url_abs":"https://arxiv.org/abs/2310.06729v3","url_pdf":"https://arxiv.org/pdf/2310.06729v3.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":"cmb-s4-iterative-internal-delensing-and-r","repo_url":"https://github.com/nextgencmb/delensalot","is_official":1,"mentioned_in_paper":1,"mentioned_in_github":1,"framework":"none","reach":null},{"paper_slug":"cmb-s4-iterative-internal-delensing-and-r","repo_url":"https://github.com/Saladino93/delensalotlight","is_official":0,"mentioned_in_paper":0,"mentioned_in_github":1,"framework":"none","reach":null},{"paper_slug":"cmb-s4-iterative-internal-delensing-and-r","repo_url":"https://github.com/Saladino93/jointmap","is_official":0,"mentioned_in_paper":0,"mentioned_in_github":1,"framework":"none","reach":{"status":"unanswered"}}],"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}