Do stochastic inhomogeneities affect dark-energy precision measurements?

TL;DR

This paper investigates how stochastic cosmological perturbations influence dark energy measurements, finding they cannot mimic dark energy effects and proposing energy flux as the optimal observable for precision cosmology.

Contribution

It introduces a covariant, gauge-invariant averaging method to assess perturbation effects on luminosity distance, showing perturbations do not significantly bias dark energy estimates.

Findings

Perturbations do not mimic dark energy effects.

Energy flux is minimally affected by perturbations at high redshift.

Stochastic variance introduces a few percent statistical error in dark energy parameters.

Abstract

The effect of a stochastic background of cosmological perturbations on the luminosity-redshift relation is computed to second order through a recently proposed covariant and gauge-invariant light-cone averaging procedure. The resulting expressions are free from both ultraviolet and infrared divergences, implying that such perturbations cannot mimic a sizable fraction of dark energy. Different averages are estimated and depend on the particular function of the luminosity distance being averaged. The energy flux, being minimally affected by perturbations at large z, is proposed as the best choice for precision estimates of dark-energy parameters. Nonetheless, its irreducible (stochastic) variance induces statistical errors on \Omega_{\Lambda}(z) typically lying in the few-percent range.