Dynamical Dark Energy in light of DESI BAO and Full-Shape Data

TL;DR

This work addresses constraining dynamical dark energy by leveraging DESI Y1 Full-Shape data in addition to DESI DR2 BAO and Planck+SNe information. It implements a DESI Y1 likelihood based on the matter power spectrum and uses MCMC with the CPL parametrization $w(a)=w_{0}+w_{a}(1-a)$ to tighten constraints on $w_{0}$ and $w_{a}$. Across three dataset combinations, incorporating DESI Y1 yields tighter 68% CL bounds, with the most notable improvement when DESY5 is included, suggesting a trend away from $\Lambda$CDM. The approach demonstrates the value of full-shape DESI information for dark energy studies and can be extended to future DESI data and other dynamical dark energy parametrizations.

Abstract

Recently, the DESI BAO data has reported a preference of dynamical dark energy (DDE) over the \LambdaCDM cosmology. Apart from the BAO data, the DDE model should be also sensitive to low-redshift measurements of the matter power spectrum data. In this study, we address this point by combining the DESI Y1 data about the matter power spectrum, extracted from the DESI Full-Shape data, with the DESI DR2 BAO data among other probes. After building the DESI Y1 likelihood, we carry out a Markov Chain Monte Carlo analysis, showing that the constraints on $w_0$ and $w_a$ with DESI Y1 data included are improved over those without it for three different datasets widely considered, especially in the case of the DESY5 sample.

Figures (3)

• Figure 1: Constraints on $w_{0}$ and $w_{a}$ in Eq.(\ref{['par']}). The contours represent the 68% and 95% credible intervals. The solid (dashed) contours represent the dataset of Planck$+$ DESI DR2 BAO$+$PantheonPlus$+$DESI Y1 with (without) the DESI Y1 Full-Shape data, showing that an inclusion of the DESI Full-Shape data slightly improves the constraints on the two parameters.
• Figure 2: Same as in Fig.\ref{['set1']} but with the dataset of Planck$+$DESI DR2 BAO$+$Union3, where the constraints on $w_{0}$ and $w_{a}$ are improved more obviously than in the previous dataset.
• Figure 3: Same as in Fig.\ref{['set1']} but with the dataset of Planck$+$DESI DR2 BAO$+$DESY5, where the improvement on $w_{0}$ and $w_{a}$ is the most significant among the three datasets considered.