{"paper":{"title":"BICEP/Keck XXI: Constraints on Early-Universe Parity Violation from Multipole-Dependent Birefringence","license":"http://creativecommons.org/licenses/by/4.0/","headline":"","cross_cats":[],"primary_cat":"astro-ph.CO","authors_text":"Aaron Steiger, Abigail G. Vieregg, Ahmed Soliman, Albert Wandui, Alessandro Schillaci, Alexis C. Weber, Amber Lennox, Anika Patel, Anna R. Polish, Annsley Greathouse, Anthony D. Turner, Antonio Fortes, Ari Jozef Cukierman, Baibhav Singari, Benjamin Schmitt, BICEP/Keck Collaboration: P. A. R. Ade, Brianna Cantrall, Brodi D. Elwood, Bryan Steinbach, Carl D. Reintsema, Carole Tucker, Chao-Lin Kuo, Cheng Zhang, Chin Lin Wong, Chris D. Sheehy, Christos Giannakopoulos, Clara Verg\\`es, Clement Pryke, Colin A. Bischoff, Cyndia Yu, David C. Goldfinger, Denis Barkats, Dominic Beck, Edward Denison, Emma Hand, George Halal, Grantland Hall, Grant Teply, Hans Boenish, Howard Hui, H. T. Nguyen, Hung-I Yang, Jae Hwan Kang, Jake Connors, James A. Grayson, James Cornelison, James J. Bock, James R. Cheshire IV, Jeffrey P. Filippini, J. M. Kovac, Johannes Hubmayr, Justin Willmert, Keith L. Thompson, Kekoa Lasko, Kent D. Irwin, King Lau, Kirit S. Karkare, Koko G. Megerian, Lingzhen Zeng, Lionel Duband, Lorenzo Minutolo, Lorenzo Moncelsi, Mandana Amiri, Margaret Lautzenhiser, Maria Salatino, Mark Halpern, Matthew A. Petroff, Michael Crumrine, Michael Echter, Min Gao, Miranda Eiben, Neil Goeckner-Wald, Nolan Maher, Paul K. Grimes, Rashmi Sudiwala, Ritoban Basu Thakur, Robert Schwarz, Roger O'Brient, Sam A. Harrison, Scott Mackey, Scott Paine, Shawn Henderson, Silvia Zhang, Sinan Kefeli, Sofia Fatigoni, Steffen Richter, Stephen Gratton, Thibault Romand, Thomas Prouve, Thuong Hoang, Tongtian Liu, Tyler St Germaine, Victor Buza, Wai Ling K. Wu, Yuka Nakato, Zeeshan Ahmed","submitted_at":"2026-03-06T19:18:01Z","abstract_excerpt":"We present the first constraints on multipole-dependent cosmic birefringence using CMB polarization data from the BK18 dataset, which combines observations from BICEP2, Keck Array, and BICEP3 at frequencies of 95, 150, and 220 GHz. Photon coupling to an axion-like field leads to the rotation of CMB polarization, inducing non-zero EB cross-correlations. We show that a multipole-dependent rotation beta(l) imprints a distinct signature in the polarization spectra that can be constrained. Specifically, we consider an Early Dark Energy (EDE) scenario in which a pseudoscalar field couples to photons"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2603.06812","kind":"arxiv","version":2},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2603.06812/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}