Observational tests of \texorpdfstring{$\Lambda(t)$}{Lambda(t)} cosmology in light of DESI DR2

TL;DR

This study tests two decaying vacuum cosmological models against recent observational data, constraining parameters and examining their physical behavior, revealing a mild deviation from the standard Lambda-CDM model.

Contribution

It provides new observational constraints on decaying vacuum models using the latest datasets, including DESI DR2, and analyzes their physical implications.

Findings

All datasets favor H_0 around 72.5-73 km/s/Mpc.

The evolution parameter n is approximately 0.30, indicating a mild deviation from Lambda-CDM.

Models show a smooth transition from deceleration to acceleration in cosmic expansion.

Abstract

In this article, we investigate two phenomenological decaying vacuum cosmological models describing the accelerated expansion of the Universe. We constrain the model parameters using a Markov Chain Monte Carlo (MCMC) technique with recent datasets, including cosmic chronometer (CC), Pantheon+SH0ES (PPS), and DESI BAO data release (DR2). Our analysis provides constraints from PPS, PPS+CC, and the joint PPS+CC+DR2 datasets for both models. All datasets favor $H_0 \simeq 72.53$--$73.01~\mathrm{Km\,s^{-1}\,Mpc^{-1}}$, while $\Omega_{m0}$ is higher with PPS alone and decreases to standard paradigm estimates with the inclusion of additional data. The evolution parameter is $n \approx 0.30$ from joint analysis, indicating a mild deviation from the $\Lambda$CDM framework. Furthermore, the physical behavior of the models is examined through the deceleration parameter and the total equation of state, confirming a smooth transition from past deceleration expansion to the present accelerated expansion.