Influence of Small-Scale Inhomogeneities on the Cosmological Consistency Tests

TL;DR

This paper investigates how small-scale inhomogeneities like clumps and voids can affect cosmological tests of the standard model, revealing potential false violations of fundamental assumptions and proposing methods to account for these effects.

Contribution

It demonstrates that local inhomogeneities can mimic violations of the cosmological principle and introduces a new reconstruction method to assess their impact within LCDM models.

Findings

Local inhomogeneities can produce false positives in consistency tests.

The amplitude of deviations helps evaluate the reliability of the Dyer-Roeder approximation.

A new method for reconstructing inhomogeneity effects in LCDM models is proposed.

Abstract

The current cosmological dark sector (dark matter plus dark energy) is challenging our comprehension about the physical processes taking place in the Universe. Recently, some authors tried to falsify the basic underlying assumptions of such dark matter-dark energy paradigm. In this Letter, we show that oversimplifications of the measurement process may produce false positives to any consistency test based on the globally homogeneous and isotropic LCDM model and its expansion history based on distance measurements. In particular, when local inhomogeneity effects due to clumped matter or voids are taken into account, an apparent violation of the basic assumptions ("Copernican Principle") seems to be present. Conversely, the amplitude of the deviations also probes the degree of reliability underlying the phenomenological Dyer-Roeder procedure by confronting its predictions with the accuracy of the weak lensing approach. Finally, a new method is devised to reconstruct the effects of the inhomogeneities in a LCDM model, and some suggestions of how to distinguish between clumpiness (or void) effects from different cosmologies are discussed.