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Investigating the $w$CDM Model with Latest DESI BAO Observations

Manisg Yadav, Archana Dixit, M. S. Barak, Anirudh Pradhan

TL;DR

This study tests a constant-$w$ dark energy model ($w_{de0}$) against DESI BAO and other CMB-independent data to assess deviations from $ ext{ΛCDM}$ and the impact on the $H_0$ tension. It employs the wCDM Friedmann relation $H^2(z)/H_0^2 = \Omega_{r0}(1+z)^4 + \Omega_{m0}(1+z)^3 + \Omega_{de0}(1+z)^{3(1+w_{de0})}$ with a parameter set $\{\omega_b,\omega_{cdm},H_0,w_{de0}\}$ and flat priors, analyzed via MCMC using CLASS+MontePython, incorporating DESI BAO, BBN, OHD, Pantheon Plus, and SH0ES data. The results show $w_{de0}$ generally near $-1$, with SH0ES data nudging it toward phantom values and SN$^+$ data toward quintessence; an inverse $w_{de0}$–$H_0$ correlation is observed. Importantly, the wCDM model reduces the $H_0$ tension from ≈$3.1\sigma$ (ΛCDM) to ≈$1\sigma$ for certain combinations, though model comparison via AIC/BIC typically favors ΛCDM, with Bayesian evidence often inconclusive. These findings demonstrate that DESI BAO and complementary low-redshift probes can constrain dark-energy dynamics and influence late-time expansion, motivating future DESI-era observations.

Abstract

In this study, we explore the impact of various combinations of CMB-independent datasets, including the recent DESI BAO measurements, on the equation of state (EoS) of dark energy and other cosmological parameters within the framework of the dynamical dark energy model ($w$CDM). Assuming a constant EoS parameter for dark energy, we derive constraints on the free parameters of the model using observational datasets such as DESI BAO, BBN, Observational Hubble Data (OHD), and Pantheon Plus (SN$^+$) $\&$ SH0ES. Our analysis examines the deviations of the $w$CDM model from the standard $Λ$CDM scenario and assesses its implications for cosmological tensions, particularly the $H_0$ tension [$\text{km} \text{s}^{-1} \text{Mpc}^{-1}$]. We find that the combination of DESI BAO + BBN + OHD + SN$^+$ (DESI BAO + BBN + OHD + SN$^+$ \&SH0ES) datasets provides constraints on $w_{\mathrm{de}0}$, suggesting a possible deviation from the cosmological constant scenario at a significance level of $1.6σ$ ($1.4σ$), respectively. Furthermore, we observe an inverse correlation between $w_{\text{de0}}$ and $H_0$, which highlights the role of dark energy dynamics in resolving the tension $H_0$ by approximately $2.1σ(0.8σ)$ from DESI BAO + BBN + OHD (DESI BAO + BBN + OHD + SN$^+$ \&SH0ES) datasets, respectively. Our findings offer valuable insights into the nature of dark energy and its influence on the cosmic expansion history, with implications for future observational efforts. We utilize the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) to evaluate our model's performance. The results indicate that the $w$CDM model demonstrates superior effectiveness.

Investigating the $w$CDM Model with Latest DESI BAO Observations

TL;DR

This study tests a constant- dark energy model () against DESI BAO and other CMB-independent data to assess deviations from and the impact on the tension. It employs the wCDM Friedmann relation with a parameter set and flat priors, analyzed via MCMC using CLASS+MontePython, incorporating DESI BAO, BBN, OHD, Pantheon Plus, and SH0ES data. The results show generally near , with SH0ES data nudging it toward phantom values and SN data toward quintessence; an inverse – correlation is observed. Importantly, the wCDM model reduces the tension from ≈ (ΛCDM) to ≈ for certain combinations, though model comparison via AIC/BIC typically favors ΛCDM, with Bayesian evidence often inconclusive. These findings demonstrate that DESI BAO and complementary low-redshift probes can constrain dark-energy dynamics and influence late-time expansion, motivating future DESI-era observations.

Abstract

In this study, we explore the impact of various combinations of CMB-independent datasets, including the recent DESI BAO measurements, on the equation of state (EoS) of dark energy and other cosmological parameters within the framework of the dynamical dark energy model (CDM). Assuming a constant EoS parameter for dark energy, we derive constraints on the free parameters of the model using observational datasets such as DESI BAO, BBN, Observational Hubble Data (OHD), and Pantheon Plus (SN) SH0ES. Our analysis examines the deviations of the CDM model from the standard CDM scenario and assesses its implications for cosmological tensions, particularly the tension []. We find that the combination of DESI BAO + BBN + OHD + SN (DESI BAO + BBN + OHD + SN \&SH0ES) datasets provides constraints on , suggesting a possible deviation from the cosmological constant scenario at a significance level of (), respectively. Furthermore, we observe an inverse correlation between and , which highlights the role of dark energy dynamics in resolving the tension by approximately from DESI BAO + BBN + OHD (DESI BAO + BBN + OHD + SN \&SH0ES) datasets, respectively. Our findings offer valuable insights into the nature of dark energy and its influence on the cosmic expansion history, with implications for future observational efforts. We utilize the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) to evaluate our model's performance. The results indicate that the CDM model demonstrates superior effectiveness.

Paper Structure

This paper contains 4 sections, 3 equations, 5 figures, 2 tables.

Table of Contents

  1. Introduction
  2. MODEL, DATA AND METHODOLOGY
  3. Results and discussion
  4. Conclusions

Figures (5)

  • Figure 1: The posterior distribution functions (PDFs) of the Hubble constant ($H_{0}$) are presented, with shaded regions indicating the constraints on $H_{0}$ along with their corresponding 1$\sigma$ intervals. These constraints are derived from SH0ES (Brout et al. 2022), SNa Ia, BBN, and DESI 2024.
  • Figure 2: 2-dimensional marginalized confidence regions at 68% and 95% C.L of $H_0$ and $w_{de0}$ for the $w$CDM models from all combination data sets are presented in Table \ref{['tab3']}. The vertical dotted black line represents $w_{de0} = -1$.
  • Figure 3: One-dimensional and two-dimensional marginalized contour plots at 68% and 95% C.L for various parameters obtained from DESI BAO+BBN, DESI BAO+BBN+OHD, DESI BAO+BBN+OHD+SN$^+$, and DESI BAO+BBN+CC+SN$^+$&SH0ES datasets with the $w$CDM model.
  • Figure 4: Two-dimensional marginalized confidence regions at 68% and 95% C.L of $\Omega_m$ and $H_0$ for the $w$CDM and $\Lambda$CDM models from all considered combination data sets are presented in Table \ref{['tab3']}. The vertical light brown band represents SH0ES $(H_0=73.04 \pm 1.04)$ measurement.
  • Figure 5: One-dimensional and two-dimensional marginalized contour plots at 68 %and 95% C.L for various parameters obtained from DESI BAO+BBN, DESI BAO+BBN+OHD, DESI BAO+BBN+OHD+SN$^+$, and DESI BAO+BBN+CC+SN$^+$&SH0ES datasets with the $\Lambda$CDM model.