Calculating the Hubble diagram by perturbation theory

TL;DR

This paper uses second-order perturbation theory to analyze how density fluctuations in a matter-dominated universe affect the Hubble diagram, causing it to broaden and mimic accelerated expansion.

Contribution

It provides a perturbative calculation of the impact of density fluctuations on light propagation and the resulting Hubble diagram in a matter-dominated universe.

Findings

Density fluctuations broaden the Hubble diagram into a strip.

Perturbations can mimic effects of accelerated cosmic expansion.

Abstract

The effect of density fluctuations upon light propagation is calculated perturbatively in a matter dominated irrotational universe. The starting point is the perturbed metric (second order in the perturbation strength), while the output is the Hubble diagram. Density fluctuations cause this diagram to broaden to a strip. Moreover, the shift of the diagram mimics accelerated expansion.