Modified Cosmology from Mass-to-Horizon Relation: Observational Bounds
Abstract
We constrain the class of modified cosmologies derived in Paper I [1] from a generalized mass-to-horizon relation (MHR) that enforces thermodynamic consistency between the Cai-Kim horizon temperature and generalized horizon entropies. The modified Friedmann equations depend on an entropy exponent m, an MHR coupling parameter γ, and an entanglement-correction amplitude fB, with standard ΛCDM recovered in the appropriate limit. Using Pantheon+/SH0ES Type~Ia supernovae, cosmic chronometers, DESI DR2 baryon acoustic oscillations, and Planck 2018 CMB distance priors, we constrain eight physically motivated sub-cases via Markov chain Monte Carlo and compare models through the Bayesian log-evidence. The entropy exponent is tightly bounded, |m−1|≲ O(10−4) when the MHR coupling is fixed (γ=1), relaxing to O(10−3) along the m-γ degeneracy, excluding any macroscopically significant departure from standard horizon thermodynamics. Freeing the MHR coupling parameter or the entanglement amplitude raises the inferred Hubble constant to h≃0.70-$0.71$, reducing the CMB-SH0ES tension from ∼4σ to ∼1.2-2.6σ, but no scenario fully resolves it within a flat universe. The Bayesian log-evidence nevertheless disfavors every extension relative to ΛCDM in all dataset combinations (−16≲Δln Z ≲−1): the improved fits obtained when the SH0ES calibration is included reflect an absorption of the Hubble tension by the additional parameters rather than genuine evidence for modified horizon entropy.
Versions
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BibTeX
@misc{prasanthan2026modified,
title = {{Modified Cosmology from Mass-to-Horizon Relation: Observational Bounds}},
author = {Pranav Prasanthan and Hussain Gohar and Vincenzo Salzano},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.18521},
eprint = {2607.18521},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.18521},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Modified Cosmology from Mass-to-Horizon Relation: Observational Bounds
AU - Pranav Prasanthan
AU - Hussain Gohar
AU - Vincenzo Salzano
PY - 2026
DA - 2026/10/24
PB - arXiv
DO - 10.48550/arxiv.2607.18521
UR - https://arxiv.org/abs/2607.18521
AB - We constrain the class of modified cosmologies derived in Paper I [1] from a generalized mass-to-horizon relation (MHR) that enforces thermodynamic consistency between the Cai-Kim horizon temperature and generalized horizon entropies. The modified Friedmann equations depend on an entropy exponent m, an MHR coupling parameter γ, and an entanglement-correction amplitude f_B, with standard ΛCDM recovered in the appropriate limit. Using Pantheon+/SH0ES Type~Ia supernovae, cosmic chronometers, DESI DR2 baryon acoustic oscillations, and Planck 2018 CMB distance priors, we constrain eight physically motivated sub-cases via Markov chain Monte Carlo and compare models through the Bayesian log-evidence. The entropy exponent is tightly bounded, |m−1|≲ O(10^−4) when the MHR coupling is fixed (γ=1), relaxing to O(10^−3) along the m-γ degeneracy, excluding any macroscopically significant departure from standard horizon thermodynamics. Freeing the MHR coupling parameter or the entanglement amplitude raises the inferred Hubble constant to h≃0.70-$0.71$, reducing the CMB-SH0ES tension from ∼4σ to ∼1.2-2.6σ, but no scenario fully resolves it within a flat universe. The Bayesian log-evidence nevertheless disfavors every extension relative to ΛCDM in all dataset combinations (−16≲Δln Z ≲−1): the improved fits obtained when the SH0ES calibration is included reflect an absorption of the Hubble tension by the additional parameters rather than genuine evidence for modified horizon entropy.
ER -