Avoidance of Big Crunch Singularity in the Q-SC-CDM model via nonminimal coupling: Theory and Data Analyses

Abstract

We investigate a class of scalar field dark energy models non-minimally coupled to gravity, characterized by a double exponential potential and parameterized coupling $\xi$. We study the cosmological dynamics for a recently proposed descending dark energy model, namely, Q-SC-CDM. Initially, we choose distinct values of coupling parameter. For some values of $\xi$, the evolution of the universe is split up into three different phases: {\it decelerated expansion (early time), accelerated expansion (late-time) and slow-contraction (future era)}, and provide Big Crunch Singularity at distant future. In other scenario, the phase of slow-contraction vanishes, cosmic acceleration is obtained at current epoch, and the universe gets de-Sitter expansion at distant future. It is remarkable to see that the Big Crunch Singularity is redundant in the later case. Next, we investigate the phase space analysis for the model under consideration. Our investigation brings new asymptotic regimes and finds stable de-Sitter solution. Eventually, we perform a comprehensive Bayesian analysis using recent cosmological observations, including Cosmic Chronometers, Type Ia Supernovae (Pantheon+ and DES-SN5YR), and Baryon Acoustic Oscillation (DESI DR2) data. The results demonstrate that the present model yield constraints on key cosmological parameters \Omega_{0m}, H_0 and the sound horizon r_d that are consistent with {\Lambda}CDM within 68\% confidence level, yet exhibit mild tension with Pantheon+ measurements. Additionally, we employ the Om(z) diagnostic test, Akaike and Bayesian Information Criteria to distinguish our model from {\Lambda}CDM. The Statistical comparison reveals moderate support for the current model.