English

Model-Independent Indication for a Localized Anomaly in the Late-Time Expansion History

Cosmology and Nongalactic Astrophysics 2026-07-14 v1 General Relativity and Quantum Cosmology

Abstract

We investigate the late-time expansion history of the Universe using a model-independent spline reconstruction of cosmological distances based on the latest DESI DR2 baryon acoustic oscillation (BAO) measurements and the DES Dovekie Type Ia supernova compilation. Comparing the reconstructed expansion history with the prediction of the Planck 2018 Λ\LambdaCDM model, we identify a localized deviation over the redshift interval 0.3z0.60.3\lesssim z\lesssim0.6, reaching a maximum significance of approximately 3.5σ3.5\sigma at z0.47z\simeq0.47. We demonstrate that this feature persists under substantial variations of the reconstruction methodology, dataset composition and sound-horizon calibration. Mock analyses further show that the reconstruction is unbiased and that the observed anomaly is unlikely to arise from reconstruction bias or miscalibrated uncertainties. If confirmed by future observations, this localized feature could point to previously unrecognized late-time physics or reveal subtle inconsistencies between early and late Universe cosmological probes.

Keywords

Cite

@article{arxiv.2607.13009,
  title  = {Model-Independent Indication for a Localized Anomaly in the Late-Time Expansion History},
  author = {Shibendu Gupta Choudhury and Purba Mukherjee and Eleonora Di Valentino and Anjan A Sen},
  journal= {arXiv preprint arXiv:2607.13009},
  year   = {2026}
}

Comments

15 pages, 5 figures, comments are welcome