Dark energy model with very large-scale inhomogeneity

TL;DR

This paper proposes a dark energy model with large-scale inhomogeneities using an ultralight scalar field, which can mimic standard cosmology and impact CMB anisotropies and luminosity distance measurements.

Contribution

It introduces a novel inhomogeneous dark energy model based on superhorizon scalar field perturbations, analyzing its evolution and observational constraints.

Findings

Model can replicate $\\Lambda$CDM cosmology with spatially dependent dark energy.

Constraints on inhomogeneity amplitude from CMB anisotropy data.

Inhomogeneities influence luminosity distance estimates.

Abstract

We consider a dynamical model for dark energy based on an ultralight mass scalar field with very large-scale inhomogeneities. This model may cause observable impacts on the anisotropic properties of the cosmic microwave background (CMB) intensity and luminosity distance. We formulate the model as the cosmological perturbations of the superhorizon scales, focusing on the local region of our universe. Moreover, we investigated the characteristic properties of the late-time evolution of inhomogeneous dark energy. Our numerical solutions show that the model can mimic the standard $\Lambda$CDM cosmology while including spatially dependent dark energy with flexible ranges of the model parameters. We put a constraint on the amplitude of these inhomogeneities of the dark energy on very large scales with the observations of the CMB anisotropies. We also discuss their influence on the estimation of the luminosity distance.