2026/07/24 by Kelvis A. Kulhkampa, Carlos H. Coimbra-Araújob, Abraão J. S. Capistrano +2
#gr-qc #astro-ph.CO
Persistent discrepancies between early- and late-Universe measurements have made cosmological tensions a major test of the standard ΛCDM model. We investigate whether an entropic generalized Chaplygin-gas cosmology, describing a unified dark sector, can modify the parameter degeneracies associated with these tensions. The model is constrained using Type Ia supernova data from PantheonPlus+SH0ES and DES--Dovekie, DESI BAO measurements, RSD growth data, compressed Planck 2018 distance priors, and a Planck lensing-amplitude prior. We find that the entropic gCg model closely reproduces the ΛCDM background expansion while introducing a controlled late-time deformation of the distance--redshift relation. This shifts the preferred (H0,Ωm,S8) region and partially reduces background-driven discrepancies, especially those involving H0. Using Tensiometer to quantify posterior shifts in the common derived parameter space (H0,Ωm,S8), we show that the displacement relative to ΛCDM occurs mainly along background-sensitive directions. The model therefore modifies the late-time expansion sector more effectively than the growth sector, leaving residual S8 discrepancies comparatively robust. These results support the possibility that the H0 and S8 tensions arise from distinct physical sectors.