Low redshift constraints on scale-covariant models

The search for a physical model which explains the observed recent acceleration of the universe is a compelling task of modern fundamental cosmology. Recently Fernandes et al. presented low redshift observational constraints on a scale invariant model by Maeder. Phenomenologically this can be interpreted as a bimetric theory with a time-dependent cosmological constant. It was shown that a matter density Omega(m) similar to 0.3 is a poor fit to the data, and the best-fit model would require a fluid with a much smaller density and a significantly positive equation of state parameter. This model is a particular case of an earlier and broader class of models by Canuto et al., which we study here. Specifically, we consider it in two distinct scenarios: as a genuine alternative to ACDM (i.e., without any cosmological constant) and as a parametric extension thereof (where both a cosmological constant and the new mechanism can coexist, and the relative contributions of both are determined by the data). We find that the first scenario can in principle fit the low-redshift data (but a good fit would require values of model parameters, such as the matter equation of state, in conflict with other data), while in the second one the deviation from ACDM is constrained to be small. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

The search for a physical model to explain the recent acceleration of the universe has led researchers to investigate a scale invariant model and its low redshift observational constraints. The findings indicate that the best-fit model requires a fluid with smaller density and a positive equation of state parameter, and this model can be considered as a particular case or a parameter extension of ACDM.