$f(Q,T)$ Gravity with Barrow Holographic Dark Energy and Massive Neutrinos: DESI DR2 Constraints and Implications for the Hubble Tension

We study a modification of symmetric teleparallel gravity in which the function $f(Q,T)$ is linear in the non-metricity scalar $Q$ and the trace $T$ of the energy-momentum tensor, combined with a Barrow holographic dark energy (BHDE) density built from the Granda-Oliveros infrared cutoff. The resulting background equations are solved in a modified version of \texttt{hi_class} and constrained with Pantheon+ supernovae, 32 cosmic chronometer $H(z)$ points, DESI DR2 baryon acoustic oscillations, and Planck 2018 CMB distance priors, sampled with MontePython. Two versions of the model are considered, one with the neutrino sector held massless and one with the sum of neutrino masses $Σm_ν$ left free. Across five data combinations, $H_0$ falls between 67.5 and 72.3 km s$^{-1}$ Mpc$^{-1}$, closer to the Planck value when cosmic chronometers dominate the fit and closer to the SH0ES value when Pantheon+ is included; adding $Σm_ν$ as a free parameter raises $H_0$ in four of the five combinations, by amounts ranging from a few hundredths of a km s$^{-1}$ Mpc$^{-1}$ up to about 1.5 km s$^{-1}$ Mpc$^{-1}$, while the CMB-only combination shifts slightly the other way, and the fit uncertainties loosen throughout. The 95% upper bound on $Σm_ν$ ranges from 0.13 to 0.22 eV depending on the data combination, comparable to standard $Λ$CDM constraints. Comparison with $Λ$CDM through the Akaike and Bayesian Information Criteria gives mixed results: the extended model is favored once Pantheon+ is included, particularly with massive neutrinos, but is disfavored for CMB-only and CMB+BAO fits, where the improvement in $χ^2$ does not offset the larger parameter count. The Barrow exponent $Δ$ stays below 0.005 throughout, and the Granda-Oliveros parameters $λ$ and $γ$ remain near 1 and 0.5 across all combinations.

Source: arXiv:2610.23957v1 - http://arxiv.org/abs/2610.23957v1 PDF: https://arxiv.org/pdf/2610.23957v1 Original Link: http://arxiv.org/abs/2610.23957v1