Coupled multiscalar field dark energy

The main aim of this paper is to present the multiscalar field components as candidates for the dark energy of the Universe and their observational constraints. We start with the canonical quintessence and phantom fields with quadratic potentials and show that a more complex model should satisfy current cosmological observations. Then, we present some implications for a combination of two fields, called quintom models. We consider two types of models: one as the sum of the quintessence and phantom potentials, and one including an interacting term between fields. We find that adding one extra degree of freedom, via the interacting term, enriches the dynamics considerably and could lead to an improvement in the fit of -2 ln Delta Lmax = 5.19 compared to ACDM. The resultant effective equation of state is now able to cross the phantom divide line and in several cases presents an oscillatory or discontinuous behavior, depending on the interaction value. The parameter constraints of the scalar field models (quintessence, phantom, quintom, and interacting quintom) are performed using cosmic chronometer, type Ia supernovae, and baryon acoustic oscillation data, and the log-Bayes factors are computed to compare the performance of the models. We show that single scalar fields may face serious trouble and hence more complex models, i.e., multiple fields are necessary.