Probing the Evolution of Dark Energy: A Joint Analysis of DESI DR2, Pantheon+, and Cosmic Chronometers

TL;DR

This study analyzes late-time cosmological data to explore whether dark energy is consistent with a cosmological constant or shows signs of evolution, finding mild evidence for dynamical dark energy.

Contribution

It provides a joint analysis of multiple datasets to test phenomenological dark energy models, highlighting potential deviations from a constant dark energy equation of state.

Findings

Allowing for a time-varying dark energy improves fit over $ ext{Lambda}$CDM.

Current data suggest a departure of the present-day equation-of-state from -1.

Dynamical dark energy models are mildly favored over $ ext{Lambda}$CDM.

Abstract

We investigate several phenomenological dark energy parameterizations using a joint analysis of late-time cosmological observations, including cosmic-chromatometer measurements of the Hubble parameter, DESI DR2 baryon acoustic oscillation data, and the Pantheon+ Type Ia supernova sample. Our results show that allowing for a time-varying dark energy equation of state significantly improves the overall fit compared to $\Lambda$CDM. The present-day equation-of-state parameter departs from the standard cosmological constant value. In contrast, the evolution parameter in two-parameter models tends to be negative, indicating a possible time dependence of dark energy. However, the constraints on the evolution remain moderate, and current data cannot clearly distinguish the specific functional form of dark energy. Model comparison using information criteria suggests that dynamical dark energy models are favored over $\Lambda$CDM, with the most straightforward one-parameter extension emerging as the most parsimonious scenario. These findings indicate a mild preference for dark energy evolution, though future high-precision observations will be required for definitive conclusions.