Fazzari, E. orcid.org/0009-0005-0594-4128, Giarè, W. orcid.org/0000-0002-4012-9285 and Di Valentino, E. orcid.org/0000-0001-8408-6961 (2026) Cosmographic footprints of dynamical dark energy. The Astrophysical Journal Letters, 996 (1). L5. ISSN: 2041-8205
Abstract
We introduce a novel cosmographic framework to trace the late-time kinematics of the Universe without assuming any underlying dynamics. The method relies on generalized Padé (2, 1) expansions around arbitrary pivot redshifts, which, compared to state-of-the-art calculations, reduce truncation errors by up to two orders of magnitude at high redshift and yield more precise constraints by defining cosmographic parameters exactly where the data lie. This avoids extrapolations, mitigates degeneracies, and enables a clean disentangling of their effects. Using the latest low-redshift datasets, we center the generalized expansion in multiple bins across z ∈ [0, 1] and obtain precise constraints on the redshift evolution of cosmographic parameters. We find that all key parameters deviate from their ΛCDM predictions in a redshift-dependent way that can be naturally explained within dynamical dark energy scenarios. The deceleration parameter q(z) follows a redshift evolution consistent with the Chevallier–Polarski–Linder (CPL) parameterization, while the generalized Om(z) diagnostic shows deviations of up to ∼4σ from the constant ΛCDM expectation, closely matching the CPL predictions. Taken together, these results point to footprints of dynamical dark energy in the kinematics of the Universe at z ≲ 1.
Metadata
| Item Type: | Article |
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| Authors/Creators: |
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| Copyright, Publisher and Additional Information: | © 2025. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence (https://creativecommons.org/licenses/by/4.0/). Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. |
| Keywords: | Deceleration parameter; Dark energy; Cosmology; Cosmological constant |
| Dates: |
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| Institution: | The University of Sheffield |
| Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Mathematical and Physical Sciences |
| Funding Information: | Funder Grant number SCIENCE AND TECHNOLOGY FACILITIES COUNCIL ST/X000621/1 |
| Date Deposited: | 07 Jan 2026 14:52 |
| Last Modified: | 07 Jan 2026 14:52 |
| Status: | Published |
| Publisher: | American Astronomical Society |
| Refereed: | Yes |
| Identification Number: | 10.3847/2041-8213/ae2917 |
| Related URLs: | |
| Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:236239 |
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