{"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/the-evolution-of-pitch-angles-of-spiral-arms","title":"The evolution of pitch angles of spiral arms","arxiv_id":"1909.10291","date":"2019-09-23","proceeding":null,"authors":["J. E. Pringle","C. L. Dobbs"],"abstract":"In spiral galaxies, the pitch angle, $\\alpha$, of the spiral arms is often proposed as a discriminator between theories for the formation of the spiral structure. In Lin-Shu density wave theory, $\\alpha$ stays constant in time, being simply a property of the underlying galaxy. In other theories (e.g tidal interaction, self-gravity) it is expected that the arms wind up in time, so that to a first approximation $\\cot \\alpha \\propto t$. For these theories, it would be expected that a sample of galaxies observed at random times should show a uniform distribution of $\\cot \\alpha$. We show that a recent set of measurements of spiral pitch angles (Yu & Ho 2018) is broadly consistent with this expectation.","url_abs":"http://arxiv.org/abs/1909.10291v1","url_pdf":"http://arxiv.org/pdf/1909.10291v1.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":"the-evolution-of-pitch-angles-of-spiral-arms","repo_url":"https://github.com/tingard/hierarchical-modelling-of-spiral-pitch-angle","is_official":0,"mentioned_in_paper":0,"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}