Non-Minimal Quintessence With Nearly Flat Potential

Abstract

We consider Brans-Dicke type nonminimally coupled scalar field as a candidate for dark energy. In the conformally transformed Einstein's frame, our model is similar to {\it coupled quintessence} model. In such models, we consider potentials for the scalar field which satisfy the slow-roll conditions: $[(1/V)(dV/d\phi)]^2 << 1$ and $(1/V)(d^2V/d\phi^2) << 1$. For such potentials, we show that the equation of state for the scalar field can be described by a universal behaviour, provided the scalar field rolls only in the flat part of the potentials where the slow-roll conditions are satisfied. Our work generalizes the previous work by Scherrer and Sen \cite{scherrer} for minimally coupled scalar field case. We have also studied the observational constraints on the model parameters considering the Supernova and BAO observational data.