σCDM coupled to radiation: Dark energy and Universe acceleration

Abstract

Recently, the Chiral Cosmological Model (CCM) coupled to cold dark matter (CDM) has been investigated as [Formula: see text]CDM model to study the observed accelerated expansion of the Universe. Dark sector fields (as Dark Energy content) coupled to cosmic dust were considered as the source of Einstein gravity in Friedmann–Robertson–Walker (FRW) cosmology. Such model had a beginning at the matter-dominated era. The purposes of our present investigation are two-fold: To extend “life” of the [Formula: see text]CDM for earlier times to radiation-dominated era and to take into account variation of the exponential potential [Formula: see text] via variation of the interaction parameter [Formula: see text]. We use Markov Chain Monte Carlo (MCMC) procedure to investigate possible values of initial conditions constrained by the measured amount of the dark matter, dark energy and radiation component today. Our analysis includes dark energy contribution to critical density, the ratio of the kinetic and potential energies, deceleration parameter, effective equation of state (EoS) and evolution of DE EoS with variation of coupling constant [Formula: see text]. A comparison with the [Formula: see text]CDM model was performed. A new feature of the model is the existence of some values of potential coupling constant, leading to a [Formula: see text]CDM solution without transition into accelerated expansion epoch.