Observational and Thermodynamic aspects of one-dimensional Dark Energy EoS parametrization models

Abstract

We investigate the observational and thermodynamic viability of Gong-Zhang (GZ) Type~I (GZ1) and Type~II (GZ2) dark-energy parametrizations using late-time cosmological probes including Type~Ia supernovae (Union3, Pantheon+SH0ES, and DES-SN5YR), DESI baryon acoustic oscillations, cosmic chronometer $H(z)$ measurements, and growth-rate data. Using Bayesian Markov Chain Monte Carlo analysis together with Akaike and Bayesian information criteria, we show that both parametrizations provide observationally consistent and phenomenologically competitive late-time alternatives to $\Lambda$CDM, while the GZ2 model generally provides tighter constraints and reduced parameter degeneracies. The reconstructed evolution of the dark-energy equation of state and coincidence parameter demonstrates that both models recover the standard matter-dominated behaviour at high redshift while producing controlled late-time deviations from the cosmological-constant scenario. A complementary cosmographic, sound-speed, and growth analysis further confirms stable late-time accelerated expansion together with physically viable perturbative behaviour. Finally, using configuration entropy as a thermodynamic probe, we show that the entropy-production rate sensitively captures the influence of dynamical dark energy on late-time structure formation while remaining consistent with standard early-time cosmology.

23 pages, 14 figures and 2 tables

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