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Non-minimally coupled quintessence with sign-switching interaction

Jia-Qi Wang, Rong-Gen Cai, Zong-Kuan Guo, Yun-He Li, Shao-Jiang Wang, Xin Zhang

Abstract

We propose a new non-minimally coupled quintessence model to account for the late-time dark energy dynamics indicated by recent DESI measurements. Within this framework, the quintessence density begins to decrease only when it starts to dominate the universe, which naturally accounts for the late-time onset of dark energy weakening. The coupling also induces a sign change in the effective energy transfer between dark matter and dark energy during cosmic evolution. While the scalar field itself remains canonical and never crosses the phantom divide, the modified evolution of the dark matter density gives rise to an effective crossing behavior in the observationally inferred dark energy sector. Compared with both $Λ$CDM and $w_0w_a$CDM models, our model is favored more strongly by current cosmological data. This work may provide a promising avenue for understanding the observational late-time weakening of dark energy and the origin of its dynamics.

Non-minimally coupled quintessence with sign-switching interaction

Abstract

We propose a new non-minimally coupled quintessence model to account for the late-time dark energy dynamics indicated by recent DESI measurements. Within this framework, the quintessence density begins to decrease only when it starts to dominate the universe, which naturally accounts for the late-time onset of dark energy weakening. The coupling also induces a sign change in the effective energy transfer between dark matter and dark energy during cosmic evolution. While the scalar field itself remains canonical and never crosses the phantom divide, the modified evolution of the dark matter density gives rise to an effective crossing behavior in the observationally inferred dark energy sector. Compared with both CDM and CDM models, our model is favored more strongly by current cosmological data. This work may provide a promising avenue for understanding the observational late-time weakening of dark energy and the origin of its dynamics.

Paper Structure

This paper contains 8 sections, 10 equations, 5 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Model Setup
  3. Methodology and Data
  4. Cosmological Constraints
  5. Discussions
  6. Dynamical Dark Energy
  7. $H_0$ tension
  8. Conclusions

Figures (5)

  • Figure 1: Background evolution of the scalar field $\varphi$ (blue line) and the coupling factor $\mathcal{A}(\varphi)$ (orange line) as a function of redshift.
  • Figure 2: Effective potential $V_{\rm eff}(\varphi)$ defined by Eq. \ref{['eq:Veff']} in the late Universe ($0<z\leq 5$), in which $\{\alpha,\beta\}=\{0.8,0.2\}$
  • Figure 3: 2-dimensional marginalized constraints on the $\beta\varphi$CDM model parameters from the combined datasets of Baseline and SN measurements from DES-Dovekie (blue), DES-Y5 (orange), and PantheonPlus (purple), respectively.
  • Figure 4: Low-redshift evolution of the energy densities and reconstructed equations of state for the scalar field, dark matter, the effective DE, and the apparent DE defined in Eq. \ref{['eq:rho_DE_eff']} and Eq. \ref{['eq:rho_DE_app']}. The phantom-divide crossing in the reconstructed $w(z)$ occurs at different redshifts depending on the bookkeeping used to define the dark-energy sector.
  • Figure 5: Cosmological constraints on $H_0$ and three model parameters $\alpha,\beta,\mathcal{A}_\mathrm{ini}$ in the $\beta\varphi\mathrm{CDM}$ model from Baseline+DES-Dovekie (blue) and Baseline+DES-Dovekie+$H_0$ (orange) datasets.