Hints for possible low redshift oscillation around the best fit $\Lambda$CDM model in the expansion history of the Universe

TL;DR

This study investigates potential low-redshift deviations from the standard $\\Lambda$CDM model in the universe's expansion history by analyzing supernova data, revealing possible oscillations that could suggest new physics or systematic effects.

Contribution

It provides the first detailed analysis of low-redshift oscillations in the expansion history using the Pantheon supernova dataset and Monte Carlo simulations, highlighting potential deviations from the standard model.

Findings

Oscillations in matter density parameter and absolute magnitude at low redshift.

Such oscillations occur in only 4-5% of simulations, indicating they are likely not due to random fluctuations.

Possible implications include inhomogeneities or scalar field oscillations beyond standard cosmology.

Abstract

We search for possible deviations from the expectations of the concordance $\Lambda$CDM model in the expansion history of the Universe by analysing the Pantheon Type Ia Supernovae (SnIa) compilation along with its Monte Carlo simulations using redshift binning. We demonstrate that the redshift binned best fit $\Lambda$CDM matter density parameter $\Omega_{0m}$ and the best fit effective absolute magnitude $\cal M$ oscillate about their full dataset best fit values with considerably large amplitudes. Using the full covariance matrix of the data taking into account systematic and statistical errors, we show that at the redshifts below $z\approx0.5$ such oscillations can only occur in 4 to 5$\%$ of the Monte Carlo simulations. While statistical fluctuations can be responsible for this apparent oscillation, we might have observed a hint for some behaviour beyond the expectations of the concordance model or a possible additional systematic in the data. If this apparent oscillation is not due to statistical or systematic effects, it could be due to either the presence of coherent inhomogeneities at low $z$ or due to oscillations of a quintessence scalar field.