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 \(fσ_8(z)\) 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 \(Λ\)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.

Figures (7)

• Figure 1: Upto $2\sigma$ ($95\%$ CL) 2D likelihood contours for the parameter space $\{H_0,\Omega_{m0},\beta_H,A_2,S_8\}$.
• Figure 2: Upto $2\sigma$ ($95\%$ CL) 2D likelihood contours for $\Lambda$CDM.
• Figure 3: Hubble parameter against redshift along with the CC data.
• Figure 4: Evolution of the Universe through the Deceleration parameter.
• Figure 5: Evolution of the Universe through effective EoS parameter.