Exploring Late-Time Cosmic Acceleration in VCDM Cosmology

Abstract

In this work, we have considered a minimally modified gravity theory that effectively reproduces VCDM-like behavior to investigate its cosmological implications. The model parameters are constrained using a combination of CC, RSD, DESI BAO DR2, and Union3 datasets. The model parameters are constrained using an MCMC framework, ensuring a robust estimation of credible intervals. We examine both background and perturbation-level observables, analyzing the Hubble parameter, deceleration parameter, effective equation of state, distance modulus, and the growth rate of cosmic structures through the \(f\sigma_8(z)\) observable. Our results show that the model successfully reproduces the observed expansion history, featuring a smooth transition in the Hubble evolution around \(z \simeq 0.3\), and consistent behaviour of cosmological parameters. The model outperforms \(\Lambda\)CDM in the statistical comparisons for the full dataset combination (CC+RSD+DESI DR2+Union3). These results highlight the potential of minimally modified gravity theories with VCDM-like dynamics as consistent and competitive alternatives to the standard cosmological paradigm.