Improved null tests of ΛCDM and FLRW in light of DESI DR2

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dc.contributor.authorDinda, Bikash
dc.contributor.authorMaartens, Roy
dc.contributor.authorClarkson, Chris
dc.date.accessioned2025-12-01T10:04:47Z
dc.date.available2025-12-01T10:04:47Z
dc.date.issued2025
dc.description.abstractThe DESI DR2 BAO data, in combination with CMB and different SNIa datasets, exclude the flat ΛCDM model at more than 2.5σ when analyzed through the w 0 w aCDM parametrization for evolving dark energy. This simple parametrization may not accurately capture the behavior of the entire redshift range at late times, which may introduce bias in the results. We use null tests that probe for deviations from flat ΛCDM at late times, independent of any specific dark energy parametrization. We provide several diagnostics for null tests and discuss their advantages and disadvantages. In particular, we derive diagnostics that improve on previous ones, such as the popular O m diagnostic. The diagnostics are derived from both background and perturbed quantities. Using the combination of DESI DR2 BAO and supernova data, with or without CMB data, we find that deviations from flat ΛCDM are at ∼1σ confidence level in most of the redshift range (more than 1σ for a few small redshift intervals in a few cases). When considering SDSS BAO data instead of DESI BAO data, in combination with PantheonPlus, with or without CMB data, we find even smaller deviations. Since spatial curvature can potentially modify the results, we also test for curvature in the general ΛCDM model and the general FLRW model. While there is slight evidence for nonzero cosmic curvature at lower redshifts in a general ΛCDM model, there is no statistically significant evidence in a general FLRW model.
dc.identifier.citationDinda, B.R., Maartens, R., Saito, S. and Clarkson, C., 2025. Improved null tests of $\Lambda $ CDM and FLRW in light of DESI DR2. arXiv preprint arXiv:2504.09681.
dc.identifier.urihttps://doi.org/10.1088/1475-7516/2025/08/018
dc.identifier.urihttps://hdl.handle.net/10566/21485
dc.language.isoen
dc.publisherInstitute of Physics
dc.subjectbaryon acoustic oscillations
dc.subjectdark energy theory
dc.subjectDeviations from flat ΛCDM
dc.subjectnonzero cosmic curvature
dc.titleImproved null tests of ΛCDM and FLRW in light of DESI DR2
dc.typeArticle

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