Hu-Sawicki f(R) Gravity in a Non-Flat Universe: Constraints from DESI-DR2, BBN, and Type Ia Supernovae
Abstract
Late-time cosmic acceleration is conventionally ascribed to a cosmological constant, though ΛCDM continues to face several theoretical difficulties that keep alternative gravity models under active consideration. This work examines the Hu-Sawicki f(R) model in a spatially non-flat background, with the modified-gravity parameter b and the curvature density Ωk both treated as free parameters, constrained using DESI-DR2 BAO, BBN, and four Type Ia supernova compilations -- PantheonPlus, PantheonPlus+SH0ES, Union3, and DESY5yr. Across all four combinations, H0 and Ωm stay close to their ΛCDM values, with a noticeable shift in H0 appearing only for the SH0ES-calibrated dataset. The parameter b departs from zero at better than 2σ in three of the four fits, most prominently for DESY5yr, whereas the SH0ES-calibrated combination alone prefers b<0. A strong positive correlation among b, H0, and Ωk underlies this shift, suggesting that curvature signatures obtained under ΛCDM can be reabsorbed into the modified-gravity sector once this additional freedom is allowed. Statistical model comparison via AIC and BIC gives a mixed picture: AIC leans toward the Hu-Sawicki model in three of the four combinations, while BIC's heavier penalty on the extra parameter favors ΛCDM in most cases, and only DESY5yr is preferred under both criteria. These findings show that the Hu-Sawicki f(R) scenario with unconstrained curvature is nonetheless a statistically feasible, if not obviously preferred, alternative to ΛCDM, and that curvature restrictions generated inside ΛCDM cannot be viewed as independent of the underlying gravity model.
Related
- Stress-testing the spatially flat Universe: nonparametric spatial curvature determination from DESI DR2
- Late-time cosmological constraints on three holographic dark energy models with DESI DR2 BAO and Type Ia supernovae
- Sound-Horizon-Agnostic Forecast for Constraints on H0 and Σmν from BAO, CMB Lensing, Supernovae and LSST-like Galaxy Lensing
- A Casimir turning point as the beginning of a small flat universe
- Hadamard states for linearized gravity on asymptotically flat spacetimes
BibTeX
@misc{verma2026husawicki,
title = {{Hu-Sawicki $f(R)$ Gravity in a Non-Flat Universe: Constraints from DESI-DR2, BBN, and Type Ia Supernovae}},
author = {Saurabh Verma and Manish Yadav and Archana Dixit and Anirudh Pradhan and M. S. Barak},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.17643},
eprint = {2609.17643},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.17643},
note = {CC0},
}
RIS
TY - UNPB
TI - Hu-Sawicki f(R) Gravity in a Non-Flat Universe: Constraints from DESI-DR2, BBN, and Type Ia Supernovae
AU - Saurabh Verma
AU - Manish Yadav
AU - Archana Dixit
AU - Anirudh Pradhan
AU - M. S. Barak
PY - 2026
DA - 2026/09/15
PB - arXiv
DO - 10.48550/arxiv.2609.17643
UR - https://arxiv.org/abs/2609.17643
AB - Late-time cosmic acceleration is conventionally ascribed to a cosmological constant, though ΛCDM continues to face several theoretical difficulties that keep alternative gravity models under active consideration. This work examines the Hu-Sawicki f(R) model in a spatially non-flat background, with the modified-gravity parameter b and the curvature density Ω_k both treated as free parameters, constrained using DESI-DR2 BAO, BBN, and four Type Ia supernova compilations -- PantheonPlus, PantheonPlus+SH0ES, Union3, and DESY5yr. Across all four combinations, H_0 and Ω_m stay close to their ΛCDM values, with a noticeable shift in H_0 appearing only for the SH0ES-calibrated dataset. The parameter b departs from zero at better than 2σ in three of the four fits, most prominently for DESY5yr, whereas the SH0ES-calibrated combination alone prefers b<0. A strong positive correlation among b, H_0, and Ω_k underlies this shift, suggesting that curvature signatures obtained under ΛCDM can be reabsorbed into the modified-gravity sector once this additional freedom is allowed. Statistical model comparison via AIC and BIC gives a mixed picture: AIC leans toward the Hu-Sawicki model in three of the four combinations, while BIC's heavier penalty on the extra parameter favors ΛCDM in most cases, and only DESY5yr is preferred under both criteria. These findings show that the Hu-Sawicki f(R) scenario with unconstrained curvature is nonetheless a statistically feasible, if not obviously preferred, alternative to ΛCDM, and that curvature restrictions generated inside ΛCDM cannot be viewed as independent of the underlying gravity model.
ER -