Mass-to-Horizon Entropic Cosmology: A Unified Thermodynamic Pathway to Cosmic Acceleration

TL;DR

This work tests a thermodynamically consistent generalization of entropic cosmology where the horizon mass obeys $M \propto L^{n}$ and the entropy scales as $S_n \propto L^{n+1}$. An entropic force on the Hubble horizon drives cosmic acceleration, and the model reduces to $\Lambda$CDM for appropriate limits, with $n=3$ reproducing a cosmological-constant behavior. By solving the background equations and the linear perturbation growth, the authors fit a joint data set that includes Pantheon+ SH0ES, DESI DR2 BAO, CMB priors, and growth measurements via $f\sigma_8(z)$, finding that the generalized models are statistically competitive with, and sometimes mildly preferred over, $\Lambda$CDM. The results show that with thermodynamic consistency, entropic cosmologies can accommodate structure formation without ad hoc growth parameters, though current data favor weak entropic corrections and near-$\Lambda$CDM behavior; future high-precision observations are needed to break degeneracies between the entropy index $n$ and the coupling parameter $\gamma$.

Abstract

We investigate the observational tests of generalized mass-to-horizon entropic cosmology by incorporating large-scale structure growth data in addition to purely geometric probes. The theoretical framework is constructed from a generalized mass-to-horizon scaling relation, $M \propto L^n$, which implies a corresponding generalized entropic functional $S_n \propto L^{n+1}$. Within this setting, cosmic acceleration arises as an emergent phenomenon driven by an entropic force acting on the cosmological horizon. While earlier studies demonstrated that these entropic cosmologies can reproduce the background expansion history of the standard $Λ$CDM model, here we present a comprehensive observational analysis that jointly employs Pantheon+ Type Ia supernova data with SH0ES calibration, DESI DR2 baryon acoustic oscillation measurements, cosmic microwave background (CMB) distance priors, and a suite of cosmological structure growth observations. A Bayesian model comparison indicates that the entropic models are statistically preferred over the conventional $Λ$CDM scenario, thereby providing strong support for an entropic origin of the observed late-time cosmic acceleration in place of a fundamental cosmological constant.