Impact of small scale inhomogeneities on observations of standard candles

TL;DR

This paper examines how small scale inhomogeneities affect standard candle observations like supernovae, using the Dyer-Roeder approach to understand potential tensions with CMB data and infer inhomogeneity properties.

Contribution

It introduces a method to determine the smoothness parameter as a function of redshift to account for inhomogeneities affecting cosmological measurements.

Findings

The smoothness parameter $\alpha(z)$ can compensate for deviations in cosmological parameters.

The range of $\alpha(z)$ satisfying physical constraints is identified.

Inhomogeneities may explain observed tensions between different cosmological observations.

Abstract

We investigate the effect of small scale inhomogeneities on standard candle observations, such as type Ia supernovae (SNe) observations. Existence of the small scale inhomogeneities may cause a tension between SNe observations and other observations with larger diameter sources, such as the cosmic microwave background (CMB) observation. To clarify the impact of the small scale inhomogeneities, we use the Dyer-Roeder approach. We determined the smoothness parameter $\alpha(z)$ as a function of the redshift $z$ so as to compensate the deviation of cosmological parameters for SNe from those for CMB. The range of the deviation which can be compensated by the smoothness parameter $\alpha(z)$ satisfying $0\leq\alpha(z)\leq1$ is reported. Our result suggests that the tension may give us the information of the small scale inhomogeneities through the smoothness parameter.