ΛCDM-Rastall cosmology revisited: constraints from a recent quasars datasample

Abstract

In this paper we study the impact of a recent quasar datasample in the constraint of the free parameters of an extension of general relativity. As a ruler to test, we use Rastall gravity in the context of background cosmology being a simple extension to general relativity. We compare the results from quasars dataset with other known samples such as cosmic chronometers, supernovae of the Ia type, baryon acoustic oscillations, HII galaxies, and also a joint analysis. Results are consistent with the standard cosmological model emphasizing that Rastall gravity is equivalent to General Relativity. According to the constraints provided from the joint sample, the age of the Universe is τU = 12.601+0.067 −0.066 Gyrs and the transition to an accelerated phase occurs at zT = 0.620 ± 0.025 in the redshift scale, being only the phase transition consistent with the standard paradigm and having a younger Universe. With the quasars sample, the universe age differs with that expected in ΛCDM having a result of τU = 11.958+0.139 −0.109 Gyrs with a transition at zT = 0.652 ± 0.032 this last consistent with standard cosmology. A remarkable result is that quasars constraints has the capability to differentiate among general relativity and Rastall gravity due to the result for the parameter λ = −2.231+0.785 −0.546. Moreover, the parameter j under quasars constraints suggests that the cause of the late universe’s acceleration is a dark energy fluid different from a cosmological constant.