Hints for possible low redshift oscillation around the best-fitting ΛCDM model in the expansion history of the Universe

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-fitting Lambda CDM matter density parameter Omega(0m) and the best-fitting effective absolute magnitude M oscillate about their full data set best-fitting 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 approximate to 0.5 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.

Automated summary

By analyzing supernovae and simulation data, we found significant fluctuations in the expansion history of the universe at low redshifts, possibly indicating behavior beyond the expectations of the concordance model.