Stringent Restriction from the Growth of Large-Scale Structure on Apparent Acceleration in Inhomogeneous Cosmological Models

TL;DR

This paper evaluates inhomogeneous cosmological models, specifically Szekeres models, against observational data, finding they cannot replicate observed late-time structure growth without including a cosmological constant, thus supporting the standard Lambda-CDM model.

Contribution

It demonstrates that Szekeres inhomogeneous models without a cosmological constant cannot match observed structure growth, reinforcing the necessity of Lambda in cosmological modeling.

Findings

Szekeres models fit expansion history without Lambda

They fail to reproduce observed late-time growth suppression

Lambda-CDM model aligns with both expansion and growth data at high confidence

Abstract

Probes of cosmic expansion constitute the main basis for arguments to support or refute a possible apparent acceleration due to different expansion rates in the universe as described by inhomogeneous cosmological models. We present in this Letter a separate argument based on results from an analysis of the growth rate of large-scale structure in the universe as modeled by the inhomogeneous cosmological models of Szekeres. We use the models with no assumptions of spherical or axial symmetries. We find that while the Szekeres models can fit very well the observed expansion history without a $\Lambda$, they fail to produce the observed late-time suppression in the growth unless $\Lambda$ is added to the dynamics. A simultaneous fit to the supernova and growth factor data shows that the cold dark matter model with a cosmological constant ($\Lambda$CDM) provides consistency with the data at a confidence level of 99.65% while the Szekeres model without $\Lambda$ achieves only a 60.46% level. When the data sets are considered separately, the Szekeres with no $\Lambda$ fits the supernova data as well as the $\Lambda$CDM does, but provides a very poor fit to the growth data with only 31.31% consistency level compared to 99.99% for the $\Lambda$CDM. This absence of late-time growth suppression in inhomogeneous models without a $\Lambda$ is consolidated by a physical explanation.