{"paper":{"title":"Sign-Switching Dark Energy: Smooth Transitions with Recent DESI DR2 Observations","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"Sign-switching dark energy models reduce the Hubble tension and fit DESI DR2 observations better than standard ΛCDM.","cross_cats":["gr-qc","hep-ph","hep-th"],"primary_cat":"astro-ph.CO","authors_text":"Be\\~nat Ibarra-Uriondo, Mariam Bouhmadi-L\\'opez","submitted_at":"2026-02-12T19:08:27Z","abstract_excerpt":"Sign-switching dark energy provides a novel mechanism for modifying the late-time expansion history of the Universe without invoking additional fields or finely tuned initial conditions. In this work, we investigate a class of background--level cosmological models in which the dark energy contribution changes sign at a transition redshift $z_\\dagger$, producing a sharp deviation from standard $\\Lambda$CDM dynamics. We confront these models with a comprehensive set of cosmological observations, including Planck 18 cosmic microwave background (CMB) measurements, DESI DR2 Baryonic Acoustic Oscill"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"the sign-switching scenario significantly alleviates the Hubble tension while obtaining better results when statistically comparing with ΛCDM, as quantified by the Akaike and Bayesian information Criteria.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The model is explored only at the background level, so the assumption that perturbations around the sign switch do not spoil the fit or introduce new tensions with structure-formation data must hold.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"Sign-switching dark energy with a transition at z_† fits recent DESI DR2, Planck CMB, and Pantheon+ data better than ΛCDM while raising the inferred Hubble constant and easing the Hubble tension.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Sign-switching dark energy models reduce the Hubble tension and fit DESI DR2 observations better than standard ΛCDM.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"b154d3896fa46b6057386a190bf32235ad87e9bd743d736817c27079ef434717"},"source":{"id":"2602.12347","kind":"arxiv","version":2},"verdict":{"id":"8e183ec3-c21f-457d-ba18-76a8b8d1a119","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-16T05:15:21.548155Z","strongest_claim":"the sign-switching scenario significantly alleviates the Hubble tension while obtaining better results when statistically comparing with ΛCDM, as quantified by the Akaike and Bayesian information Criteria.","one_line_summary":"Sign-switching dark energy with a transition at z_† fits recent DESI DR2, Planck CMB, and Pantheon+ data better than ΛCDM while raising the inferred Hubble constant and easing the Hubble tension.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The model is explored only at the background level, so the assumption that perturbations around the sign switch do not spoil the fit or introduce new tensions with structure-formation data must hold.","pith_extraction_headline":"Sign-switching dark energy models reduce the Hubble tension and fit DESI DR2 observations better than standard ΛCDM."},"references":{"count":124,"sample":[{"doi":"","year":null,"title":"Although BAO data are also sensitive to Ω m, an additional prior is required to fully break the degeneracy between the expansion rate and the sound-horizon scale","work_id":"7355d246-e5cc-4c45-aba0-30c9e4420194","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2018,"title":"Baryon Acoustic Oscillations BAO constitute a powerful observational probe for constraining cosmological parameters, particularly when combined with complementary datasets such as the CMB. The charact","work_id":"f62f286c-348e-4ea7-8714-e1c4bd777aca","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":null,"title":"Cosmic Microwave Background The CMB is one of the most powerful observational tools for studying the early Universe, carrying detailed information about cosmological evolution from the epoch of photon","work_id":"bd008f6a-1b02-462d-a6b3-975c45e6c6a8","ref_index":3,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":null,"title":"Fitting the models to these data reveals a significant shift in the inferred value ofH 0 relative to ΛCDM","work_id":"0fe9cf54-ca96-4d3e-b896-c3f73fbc8c4b","ref_index":4,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":null,"title":"The parametersH 0 and Ω m0 appear to increase across all models relative to ΛCDM, particularly in LΛCDM and SSCDM","work_id":"32883c5c-0e80-4c2b-be0e-a9a7443535a1","ref_index":5,"cited_arxiv_id":"","is_internal_anchor":false}],"resolved_work":124,"snapshot_sha256":"0181fcf4783b90b38e0639528e21d0e1ff23f9324cba8be0934301ae5cc7be61","internal_anchors":46},"formal_canon":{"evidence_count":2,"snapshot_sha256":"cc6fc8405e3e483b2df49e8aa10a1438d784ac43439697222b78cf2b3aa51ac6"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}