{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"d69da848d667086e2f39611253ba64ddf65e0dc490adaddf13cc087be3dc1731","created":"2026-10-03T07:18:02Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"6ad8fb78b6d8f61630894d6d9558aa2c30f97974abc4fb80c78a3ef090b834bc","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"cosmo.dark-energy.evolving-dark-energy","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"plain":"If dark energy is the energy of empty space it never changes, but if it comes from a slowly rolling field its density should drift. New maps of millions of galaxies hint at a drift.","posed_since":"1998","precise":"In the parametrization $w(a) = w0 + wa (1 - a)$, with w the pressure-to-density ratio and a the scale factor, determine whether $(w0, wa) = (-1, 0)$ is excluded at $5\\sigma$ by baryon acoustic oscillations, CMB and type Ia supernovae. DESI DR2 BAO plus CMB plus DES-Dovekie supernovae give $w0 = -0.803 \\pm 0.054, wa = -0.72 \\pm 0.21$. Answer yes or no at $5\\sigma$ with datasets whose systematics are independently validated.","problem_ref":null,"references":"","settled_by":"Final DESI BAO, Euclid clustering and Rubin LSST supernovae combined with CMB, giving a $5\\ \\sigma$ result stable across supernova samples.","status_note":"DESI DR2 BAO plus CMB gives $3.1\\sigma$ (2025); adding supernovae gives $2.8\\sigma$ (Pantheon+), $3.8\\sigma$ (Union3) and $3.2\\sigma$ (DES-Dovekie, 2025).","title":"Is the dark energy density constant in 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