Observational constraints on Diffusion Cosmologies in Unimodular Gravity from DESI DR2
Abstract
Diffusion functions in unimodular gravity induce a dynamical effective cosmological constant, providing an appealing framework in light of recent DESI observations. In this work, we investigate the observational viability of a general class of diffusion models using baryon acoustic oscillation measurements from DESI DR2, Type Ia supernova compilations (Pantheon+, DES-Dovekie, and DESY5), and Cosmic Chronometer data. We find that diffusion models systematically achieve lower best-fit χ2 values than ΛCDM across all dataset combinations considered, indicating a modest but persistent improvement in goodness of fit. Nevertheless, the reduction in χ2 is insufficient to offset the larger parameter space, leading standard information criteria to favor the simpler ΛCDM model. Despite this result, all dataset combinations consistently prefer a nonvanishing diffusion contribution corresponding to approximately 20% of the present dark-energy budget, with a posterior probability P(fQ>0.05) =96.78%. From an observational perspective, diffusion models therefore remain a viable extension of the standard cosmological scenario and motivate the exploration of simpler diffusion parameterizations, particularly in light of upcoming high-precision cosmological surveys.
Related
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BibTeX
@misc{gomez2026observational,
title = {{Observational constraints on Diffusion Cosmologies in Unimodular Gravity from DESI DR2}},
author = {Gabriel Gomez and Guillermo Palma and Norman Cruz},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.10574},
eprint = {2609.10574},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.10574},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Observational constraints on Diffusion Cosmologies in Unimodular Gravity from DESI DR2
AU - Gabriel Gomez
AU - Guillermo Palma
AU - Norman Cruz
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.10574
UR - https://arxiv.org/abs/2609.10574
AB - Diffusion functions in unimodular gravity induce a dynamical effective cosmological constant, providing an appealing framework in light of recent DESI observations. In this work, we investigate the observational viability of a general class of diffusion models using baryon acoustic oscillation measurements from DESI DR2, Type Ia supernova compilations (Pantheon+, DES-Dovekie, and DESY5), and Cosmic Chronometer data. We find that diffusion models systematically achieve lower best-fit χ^2 values than ΛCDM across all dataset combinations considered, indicating a modest but persistent improvement in goodness of fit. Nevertheless, the reduction in χ^2 is insufficient to offset the larger parameter space, leading standard information criteria to favor the simpler ΛCDM model. Despite this result, all dataset combinations consistently prefer a nonvanishing diffusion contribution corresponding to approximately 20% of the present dark-energy budget, with a posterior probability P(f_Q>0.05) =96.78%. From an observational perspective, diffusion models therefore remain a viable extension of the standard cosmological scenario and motivate the exploration of simpler diffusion parameterizations, particularly in light of upcoming high-precision cosmological surveys.
ER -