Stress-testing the spatially flat Universe: nonparametric spatial curvature determination from DESI DR2
Abstract
We present a nonparametric determination of spatial curvature using only late-time geometrical probes. Under a Gaussian Process smoothness prior, we jointly constrain the dimensionless expansion history and ΩK, combining three Type Ia Supernovae (SNeIa) samples with either DESI DR2 line-of-sight baryon acoustic oscillations (BAO) or cosmic chronometers (CC) data. From our baseline SNeIa+BAO analyses we find ΩK=0.219+0.110−0.111, ΩK=0.330+0.098−0.150 and ΩK=0.260+0.124−0.127 for the PantheonPlus, DES Dovekie and Union3 SNeIa samples respectively. These nonparametric results mildly favour an open Universe, supporting recent hints in this direction, and improve on the sensitivity of a previous application of the method by up to a factor of ∼ 2.5. We find consistent constraints combining SNeIa and CC, whereas restricting SNeIa data to the redshift range covered by BAO somewhat weakens the constraints and shifts the PantheonPlus central value to ΩK<0. Our results depend only on late-time relative distances and expansion rates, making them insensitive to the absolute distance scale calibration, while relying neither on Cosmic Microwave Background data nor on a parametric dark energy model.
Related
- The Euler Universe: A Relational Phase Framework for Cosmology — Construction, Philosophy, and Stress-Testing of the Spiral U(θ) = e^((λ+i)θ)
- KiDS J1447-0149: The first spatially resolved spectroscopy of a relic galaxy beyond the local universe. An old high-dispersion core embedded in a compact rotating stellar structure
- Testing the Isotropy of the Universe with the CHIME/FRB Catalog I
- Testing dark matter models and modified gravity theories with spatially resolved HI observations
- New Tsallis holographic dark energy with the Granda-Oliveros cutoff in a non-flat universe: curvature tracking and DESI DR2 constraints
BibTeX
@misc{turner2026stresstesting,
title = {{Stress-testing the spatially flat Universe: nonparametric spatial curvature determination from DESI DR2}},
author = {Hannah C. Turner and Suhail Dhawan and Sunny Vagnozzi and Alice Townsend and Peter Massey},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22470},
eprint = {2609.22470},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22470},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Stress-testing the spatially flat Universe: nonparametric spatial curvature determination from DESI DR2
AU - Hannah C. Turner
AU - Suhail Dhawan
AU - Sunny Vagnozzi
AU - Alice Townsend
AU - Peter Massey
PY - 2026
DA - 2026/09/18
PB - arXiv
DO - 10.48550/arxiv.2609.22470
UR - https://arxiv.org/abs/2609.22470
AB - We present a nonparametric determination of spatial curvature using only late-time geometrical probes. Under a Gaussian Process smoothness prior, we jointly constrain the dimensionless expansion history and Ω_K, combining three Type Ia Supernovae (SNeIa) samples with either DESI DR2 line-of-sight baryon acoustic oscillations (BAO) or cosmic chronometers (CC) data. From our baseline SNeIa+BAO analyses we find Ω_K=0.219^+0.110_−0.111, Ω_K=0.330^+0.098_−0.150 and Ω_K=0.260^+0.124_−0.127 for the PantheonPlus, DES Dovekie and Union3 SNeIa samples respectively. These nonparametric results mildly favour an open Universe, supporting recent hints in this direction, and improve on the sensitivity of a previous application of the method by up to a factor of ∼ 2.5. We find consistent constraints combining SNeIa and CC, whereas restricting SNeIa data to the redshift range covered by BAO somewhat weakens the constraints and shifts the PantheonPlus central value to Ω_K<0. Our results depend only on late-time relative distances and expansion rates, making them insensitive to the absolute distance scale calibration, while relying neither on Cosmic Microwave Background data nor on a parametric dark energy model.
ER -