Constraints on interacting dark energy models through cosmic chronometers and Gaussian process

Abstract

Energy flows between dark energy and dark matter may alleviate the Hubble tension and mitigate the coincidence problem. In this paper, after reconstructing the redshift evolution of the Hubble function by adopting Gaussian process techniques, we estimate the best-fit parameters for some flat Friedmann cosmological models based on a Modified Chaplygin Gas interacting with dark matter. In fact, the expansion history of the Universe will be investigated because passively evolving early galaxies constitute cosmic chronometers. An estimate for the present-day values of the deceleration parameter, adiabatic speed of sound within the dark energy fluid, effective dark energy, and dark matter equation of state parameters is provided. By this, we mean that the interaction term between the two dark fluids, which breaks the Bianchi symmetries, will be interpreted as an effective contribution to the dark matter pressure similarly to the framework of the \lq\lq Generalized Dark Matter". Fixing a certain value for the dark matter abundance at the present day as initial condition will allow us to investigate whether the estimate of the Hubble constant is sensitive to the dark matter - dark energy coupling. We will also show that the cosmic chronometers data favor a hot dark matter, and that our findings are in agreement with the Le Ch\^atelier-Braun principle according to which dark energy should decay into dark matter (and not vice versa).Comment: 14 pages, 2 figure