ABSTRACT In this paper, we present an alternative to standard dark energy (DE), where the vacuum energy density (VED) decays and generates the dark matter (DM) via gravitationally induced creation. This decay is considered as an irreversible energy flow maintaining the thermodynamic equilibrium through the constant entropy per particle. Motivated by quantum field theoretic considerations of vacuum decay and adiabatic matter creation, we analyze both the background dynamics and the growth rate of perturbations. The model is confronted with diverse datasets, including cosmic chronometers, Pantheon Type Ia supernovae (SNIa), Baryon acoustic oscillations, cosmic microwave background distance priors, weighted linear growth rate measurements and the local R22 value of , with parameter estimation performed via Markov Chain Monte Carlo (MCMC) methods. Model comparison is performed using the Akaike information criterion (AIC), the Deviance information criterion (DIC), and Bayesian evidence quantified through the Bayes factor. Our results show a consistent transition from a decelerated to an accelerated expansion phase, with present Hubble parameter estimates lying between the Planck and SH0ES values. The structure growth parameter is also compatible with Planck 2018 and recent weak lensing surveys. A thermodynamic analysis confirms consistency with the generalized second law (GSL), and including Casimir contributions provides further insights into the model's dynamics. Overall, the proposed model effectively captures the Universe's evolution at both theoretical and observational levels.
Chander et al. (Wed,) studied this question.
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