Exploring Late-Time Cosmic Acceleration in VCDM Cosmology

TL;DR

This paper investigates a minimally modified gravity model mimicking VCDM to explain late-time cosmic acceleration, constrained by multiple datasets, showing it fits observations well and may outperform DM.

Contribution

It introduces a minimally modified gravity model with VCDM-like behavior and demonstrates its consistency with cosmological data, offering a competitive alternative to DM.

Findings

The model reproduces the observed expansion history with a smooth transition around z  0.3.

It fits the combined datasets better than DM in statistical comparisons.

The model remains consistent at both background and perturbation levels.

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.