Entropic Chaplygin-Gas cosmology and late-universe tension diagnostics

Persistent discrepancies between early- and late-Universe measurements have made cosmological tensions a major test of the standard CDM 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 CDM background expansion while introducing a controlled late-time deformation of the distance--redshift relation. This shifts the preferred (H 0, m,S 8) region and partially reduces background-driven discrepancies, especially those involving H 0. Using Tensiometer to quantify posterior shifts in the common derived parameter space (H 0, m,S 8), we show that the displacement relative to CDM occurs mainly along background-sensitive directions. The model therefore modifies the late-time expansion sector more effectively than the growth sector, leaving residual S 8 discrepancies comparatively robust. These results support the possibility that the H 0 and S 8 tensions arise from distinct physical sectors.