Hints for possible low redshift oscillation around the best fit ΛCDM model in the expansion history of the universe

Abstract

We search for possible deviations from the expectations of the concordance ΛCDM 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 ΛCDM matter density parameter Ω0m 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 ≈ 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.

Observational constraints on the deceleration parameter in a tilted universe

“…In this subsection, we present only the derived results of the Python code, however the two publicly available codes are fully consistent with each other. In particular, for the standard ΛCDM scenario we obtain M = 23.809 ± 0.011 and Ω 0m = 0.299 ± 0.022 (see the first row of Table I) in agreement with previous studies [9,77,78,80].…”

“…where H 0 = 100h km sec −1 M pc −1 . Even though this degenerate combination is marginalized in most cases [9,76], recent studies [77][78][79][80] argue that this process may lead to physical information loss, since a physical model with an abrupt transition on the absolute magnitude M at a low redshift z t has the potential to alleviate simultaneously the H 0 and growth tensions [81][82][83][84][85][86][87][88]. Hence, we decide to use this degenerate parameter in the minimization process.…”

Running Hubble tension and a H0 diagnostic

“…2 of [49], but there the data used is intrinsically low redshift, whereas our diagnostic comprises Planck MCMC chains: the diagnostic mixes low and high redshifts. One also observes wiggles in matter density Ω m0 in the Pantheon dataset when it is binned according to redshift [54][55][56]. This observation is backed up by the compressed EðzÞ data reported originally in [57].…”

Is the Hubble crisis connected with the extinction of dinosaurs?

“…★ leandros@uoi.gr 2021; Kazantzidis et al 2021;Sapone et al 2021;Dainotti et al 2021). It is therefore becoming increasingly likely that it is due to new physics and an extension of ΛCDM is required to explain this mismatch (Di Valentino et al 2021;Perivolaropoulos & Skara 2021a).…”