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Interacting dark sector with variable vacuum energy

Luis P. Chimento, Martín G. Richarte, Iván E. Sánchez García

TL;DR

The paper studies a flat FRW cosmology in which dark matter exchanges energy with a variable vacuum energy through a nonlinear coupling $Q=\alpha\,\rho'\rho$, while baryons and radiation are decoupled. Solving the dark-sector dynamics yields a total-density solution $\rho(a)$ and a variable vacuum energy $\rho_x=[\alpha\rho^2/2+{\cal D}]=\Lambda$, producing a history from radiation and baryon domination to de Sitter phase. A likelihood analysis using updated $H(z)$ data provides best-fit cosmological parameters (e.g., $H_0\sim70.3$–$70.8$, $\Omega_{x0}\sim0.74$, $\Omega_{m0}\sim0.20$, $\Omega_{b0}\sim0.04$–$0.06$, $\alpha\sim10^{-7}$–$10^{-6}$, $\gamma_m\sim1.01$–$1.04$) with $\chi^2_{\rm dof}\lesssim0.75$, while demanding early-dark-energy bounds. The results yield $\Omega_{\rm x}(z\simeq1100)\in[10^{-6},10^{-5}]$ and $\Omega_{\rm x}(z\simeq10^{10})<0.04$ at $1\sigma$, ensuring Planck and BBN viability and supporting the model's compatibility with future Euclid and CMBPol constraints.

Abstract

We examine a cosmological scenario where dark matter is coupled to a variable vacuum energy while baryons and photons are two decoupled components for a spatially flat Friedmann-Robertson-Walker spacetime. We apply the $χ^{2}$ method to the updated observational Hubble data for constraining the cosmological parameters and analyze the amount of dark energy in the radiation era. We show that our model fulfills the severe bound of $Ω_{x}(z\simeq 1100)<0.009$ at the $2σ$ level, so it is consistent with the recent analysis that includes cosmic microwave background anisotropy measurements from the Planck survey, the Atacama Cosmology Telescope, and the South Pole Telescope along with the future constraints achievable by the Euclid and CMBPol experiments, and fulfills the stringent bound $Ω_{x}(z\simeq 10^{10})<0.04$ at the $2σ$ level in the big-bang nucleosynthesis epoch.

Interacting dark sector with variable vacuum energy

TL;DR

The paper studies a flat FRW cosmology in which dark matter exchanges energy with a variable vacuum energy through a nonlinear coupling , while baryons and radiation are decoupled. Solving the dark-sector dynamics yields a total-density solution and a variable vacuum energy , producing a history from radiation and baryon domination to de Sitter phase. A likelihood analysis using updated data provides best-fit cosmological parameters (e.g., –, , , –, –, –) with , while demanding early-dark-energy bounds. The results yield and at , ensuring Planck and BBN viability and supporting the model's compatibility with future Euclid and CMBPol constraints.

Abstract

We examine a cosmological scenario where dark matter is coupled to a variable vacuum energy while baryons and photons are two decoupled components for a spatially flat Friedmann-Robertson-Walker spacetime. We apply the method to the updated observational Hubble data for constraining the cosmological parameters and analyze the amount of dark energy in the radiation era. We show that our model fulfills the severe bound of at the level, so it is consistent with the recent analysis that includes cosmic microwave background anisotropy measurements from the Planck survey, the Atacama Cosmology Telescope, and the South Pole Telescope along with the future constraints achievable by the Euclid and CMBPol experiments, and fulfills the stringent bound at the level in the big-bang nucleosynthesis epoch.

Paper Structure

This paper contains 4 sections, 13 equations, 3 figures, 2 tables.

Table of Contents

  1. Introduction
  2. The model
  3. Observational Hubble data constraints
  4. Summary

Figures (3)

  • Figure 1: Two-dimensional C.L. associated with $1\sigma$, $2\sigma$ for different $\theta$ planes.
  • Figure 2: Comparison of Hubble parameter, dark energy and dark matter amounts , with estimates of $±\sigma$ errors, from a number of different methods.
  • Figure 3: Upper panel: Plot of $\Omega_{\rm x}$ and $\Omega_{\rm m}$ in terms of the redshift $z$. Lower panel: Plot $\Omega_{\rm b}$, $\Omega_{\rm r}$, ${\rm w}_{\rm eff t}$, ${\rm w}_{\rm eff x}$, and $q$ in terms of the redshift $z$.