Hints of Primordial Magnetic Fields at Recombination and Implications for the Hubble Tension

Hints of Primordial Magnetic Fields at Recombination and Implications for the Hubble Tension | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Hints of Primordial Magnetic Fields at Recombination and Implications for the Hubble Tension Levon Pogosian, Karsten Jedamzik, Tom Abel This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6248021/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 12 Dec, 2025 Read the published version in Nature Astronomy → Version 1 posted You are reading this latest preprint version Abstract Primordial Magnetic Fields (PMFs), long studied as potential relics of the early Universe, accelerate the recombination process and have been proposed as a possible way to relieve the Hubble tension. However, previous studies relied on simplified toy models. In this study, for the first time, we use the recent high-precision evaluations of recombination with PMFs, incorporating full magnetohydrodynamic (MHD) simulations and detailed Lyman-alpha radiative transfer, to test PMF-enhanced recombination (bΛCDM) against observational data from the cosmic microwave background (CMB), baryon acoustic oscillations (BAO), and Type Ia supernovae (SN). Focusing on non-helical PMFs with a Batchelor spectrum, we find a preference for present-day total field strengths of approximately 5-10 pico-Gauss. Depending on the dataset combination, this preference ranges from mild (∼ 1.8σ with Planck + DESI) to moderate (∼ 3σ with Planck + DESI + SH0EScalibrated SN) significance. The bΛCDM has Planck + DESI χ 2 values equal or better than those of the ΛCDM model while predicting a higher Hubble constant. The favored field strengths align closely with those required for cluster magnetic fields to originate entirely from primordial sources, without the need for additional dynamo amplification or stellar magnetic field contamination. Future high-resolution CMB temperature and polarization measurements will be crucial for confirming or further constraining the presence of PMFs at recombination. Physical sciences/Physics/Astronomy and astrophysics/Cosmology Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Cosmology Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Published Journal Publication published 12 Dec, 2025 Read the published version in Nature Astronomy → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6248021","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":446235392,"identity":"664929c9-9af9-44de-aeef-dd2c9d5c9715","order_by":0,"name":"Levon Pogosian","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAm0lEQVRIiWNgGAWjYBACPjBZwcBPvBY2MHmGQbKBNC2MbSRpYe8xfFw4r07C4ADzww/EaeE5Y2w8c9thoBY2YwnitEikpUnzbjtQZ3CAh4FILfLPgFrmgBzGw/yDSFuYj0nzNjCDtLARaQtP8mFjnmOHJSQPs5lZEKWFn/1g42OemjoJvuPNj28QpQUBmElUPwpGwSgYBaMADwAAr8AkYyIdGmsAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0001-5108-0854","institution":"Simon Fraser University","correspondingAuthor":true,"prefix":"","firstName":"Levon","middleName":"","lastName":"Pogosian","suffix":""},{"id":446235393,"identity":"3e060707-9242-4d9f-93a5-5f01bc0b977f","order_by":1,"name":"Karsten Jedamzik","email":"","orcid":"","institution":"Laboratoire de Univers et Particules de Montpellier","correspondingAuthor":false,"prefix":"","firstName":"Karsten","middleName":"","lastName":"Jedamzik","suffix":""},{"id":446235394,"identity":"9e0e7042-b4a1-465d-bc85-27f9554e247a","order_by":2,"name":"Tom Abel","email":"","orcid":"","institution":"Kavli Institute for Particle Astrophysics and Cosmology","correspondingAuthor":false,"prefix":"","firstName":"Tom","middleName":"","lastName":"Abel","suffix":""}],"badges":[],"createdAt":"2025-03-17 23:45:57","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6248021/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6248021/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41550-025-02737-x","type":"published","date":"2025-12-12T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":98118548,"identity":"89e5a0b8-bce3-4b79-b275-42d0b8fedba7","added_by":"auto","created_at":"2025-12-13 08:05:22","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1870112,"visible":true,"origin":"","legend":"Article File","description":"","filename":"paperv1.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6248021/v1_covered_a6ce9b08-0c97-4504-abc9-9f63fc95105e.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Hints of Primordial Magnetic Fields at Recombination and Implications for the Hubble Tension","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6248021/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6248021/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePrimordial Magnetic Fields (PMFs), long studied as potential relics of the early Universe, accelerate the recombination process and have been proposed as a possible way to relieve the Hubble tension. 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