Exploring Rényi Entropic Cosmology Constrained by DESI DR2 BAO and Complementary Late-Time Observations

Abstract

We investigate the late-time cosmological viability of Rényi entropic cosmology (REC) by confronting its modified Friedmann dynamics with DESI DR2 BAO, cosmic chronometers, gravitational-wave standard sirens, redshift-space distortions, and two independent Type Ia supernova compilations, PantheonPlus and Union3. Unlike earlier works, we obtain a stringent constraint on the Rényi parameter $\lambda \sim (3.7\text{–}3.8)\times 10^{-124}$, with the resulting value even satisfying recent Big Bang Nucleosynthesis and baryogenesis bounds. Across all observational combinations, REC yields $H_0\simeq 68.2$--$68.4$ $km{s}^{-1}Mp{c}^{-1}$ and ${\Omega }_{m0}\simeq 0.291$--$0.295$, with a transition from deceleration to acceleration at $z_{\mathrm{tr}}\simeq 0.66$--$0.68$. The effective equation of state remains quintessence-like, with $w_{\mathrm{eff}}(0)\simeq -0.68$, and does not cross the phantom boundary. REC provides a modest improvement in the minimum ${\chi }^2$ relative to $\Lambda$CDM, while the AIC, DIC, BIC, and Bayesian evidence indicate that the preference for REC is statistically competitive but not decisive. Conclusively, the results show that Rényi entropy can produce a controlled modification of the late-time expansion history while remaining observationally close to $\Lambda$CDM.

17 pages, 4 figures, and 6 tables (Some new datasets have been added)