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Observational constraints on dark energy model

Yungui Gong

TL;DR

This work tests a quintessence class with the general relation $V(Q)=β\,dotQ^2+C$ in a flat, accelerating universe, encompassing hyperbolic and double-exponential potentials. By combining Type Ia supernova data and the CMB shift parameter from WMAP, it constrains the primary cosmological parameters $Ω_{m0}$, $ω_{Q0}$, and $β$, and derives the transition redshift $z_T$ at which cosmic expansion changed from deceleration to acceleration. The results tend to favor ΛCDM-like behavior ($Ω_{m0}≃0.3$, $ω_{Q0}≃-1$, $β≃0.5$) but allow modest evolution in $ω_Q(z)$, with model-independent analyses indicating $Ω_{m0}≈0.4$ and $ω_{Q0}≈-1.4$ and $z_T≈0.37$. Overall, the data are consistent with a dark-energy sector that is close to, but not necessarily exactly, a cosmological constant, and the findings support a possible metamorphosis of dark energy over cosmic history.

Abstract

The recent observations support that our universe is flat and expanding with acceleration. A quintessence model with a general relation between the quintessence potential and the quintessence kinetic energy was proposed to explain the phenomenon. The dark energy potential includes both the hyperbolic and the double exponential potentials. We analyze this model in detail by using the recent supernova and the first year Wilkinson Microwave Anisotropy Probe (WMAP) observations. For a flat universe dominated by a dark energy with constant $ω$ which is a special case of the general model, we find that $Ω_{\rm m0}=0.30^{+0.06}_{-0.08}$ and $ω_{\rm Q}\le -0.82$, and the turnaround redshift $z_{\rm T}$ when the universe switched from the deceleration phase to the acceleration phase is $z_{\rm T}=0.65$. For the general model, we find that $Ω_{\rm m0}\sim 0.3$, $ω_{\rm Q0}\sim -1.0$, $β\sim 0.5$ and $z_{\rm T}\sim 0.67$. A model independent polynomial parameterization is also considered, the best fit model gives $Ω_{\rm m0}=0.40\pm 0.14$, $ω_{\rm Q0}=-1.4$ and $z_{\rm T}=0.37$.

Observational constraints on dark energy model

TL;DR

This work tests a quintessence class with the general relation in a flat, accelerating universe, encompassing hyperbolic and double-exponential potentials. By combining Type Ia supernova data and the CMB shift parameter from WMAP, it constrains the primary cosmological parameters , , and , and derives the transition redshift at which cosmic expansion changed from deceleration to acceleration. The results tend to favor ΛCDM-like behavior (, , ) but allow modest evolution in , with model-independent analyses indicating and and . Overall, the data are consistent with a dark-energy sector that is close to, but not necessarily exactly, a cosmological constant, and the findings support a possible metamorphosis of dark energy over cosmic history.

Abstract

The recent observations support that our universe is flat and expanding with acceleration. A quintessence model with a general relation between the quintessence potential and the quintessence kinetic energy was proposed to explain the phenomenon. The dark energy potential includes both the hyperbolic and the double exponential potentials. We analyze this model in detail by using the recent supernova and the first year Wilkinson Microwave Anisotropy Probe (WMAP) observations. For a flat universe dominated by a dark energy with constant which is a special case of the general model, we find that and , and the turnaround redshift when the universe switched from the deceleration phase to the acceleration phase is . For the general model, we find that , , and . A model independent polynomial parameterization is also considered, the best fit model gives , and .

Paper Structure

This paper contains 5 sections, 12 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Model Review
  3. Methodology
  4. Results
  5. Model-independent Results

Figures (4)

  • Figure 1: The confidence contours of $\Omega_{\rm m0}$ and $\omega_{\rm Q}$ for the $C=0$ model. The left upper panel is the 68%, 95% and 99% confidence regions fitted from Knop sample. The right upper panel is the 68%, 95%, 99% confidence regions fitted from Riess gold sample, the left lower panel is the 68%, 95% and 99% confidence regions fitted from Riess gold and silver sample. The right lower panel is the 68%, 95%, 99% confidence regions fitted from Riess gold sample and WMAP data.
  • Figure 2: The 68%, 95% and 99% confidence contours of $\Omega_{\rm m0}$ and $\omega_{\rm Q0}$ for $\beta=1/2$. The left panel shows fits to Knop sample and the right panel shows fits to Riess gold sample.
  • Figure 3: The 68%, 95% and 99% confidence contours of $\Omega_{\rm m0}$ and $\omega_{\rm Q0}$ for $\beta=1/2$ with Riess gold sample and WMAP data.
  • Figure 4: The best supernova and WMAP data fits to the polynomial model and linear model. The left panel shows Riess gold sample and WMAP data fits to the two parameter polynomial model, the light black lines are for $\Omega_{\rm Q}$ and the dark balck lines for $\omega_{\rm Q}$, the solid lines are from the best fit. The right panel shows Riess gold sample and WMAP data fits to the two parameter linear model of $\omega_{\rm Q}$, the solid lines are from the best fit, the light black lines are for the linear model and the dark black lines are for the stable model. The dashed lines define the 1$\sigma$ boundaries.