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

Understand

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.