Roles of dark energy perturbations in the dynamical dark energy models: Can we ignore them?

TL;DR

This paper emphasizes the critical importance of including dark energy perturbations in dynamical dark energy models, demonstrating that neglecting them leads to inconsistent results and gauge-dependent deviations in observable power spectra.

Contribution

It highlights the necessity of accounting for dark energy perturbations in scalar field and modified gravity models to ensure observational consistency and gauge invariance.

Findings

Ignoring dark energy perturbations causes gauge-dependent power spectrum deviations.

Including perturbations yields consistent, gauge-invariant predictions.

Neglecting perturbations can lead to incorrect interpretations of observational data.

Abstract

We show the importance of properly including the perturbations of the dark energy component in the dynamical dark energy models based on a scalar field and modified gravity theories in order to meet with present and future observational precisions. Based on a simple scaling scalar field dark energy model, we show that observationally distinguishable substantial differences appear by ignoring the dark energy perturbation. By ignoring it the perturbed system of equations becomes inconsistent and deviations in (gauge-invariant) power spectra depend on the gauge choice.