A quintessence scalar field in Brans-Dicke theory

Abstract

It is shown that a minimally coupled scalar field in Brans-Dicke theory yields a non-decelerated expansion for the present universe for open, flat and closed Friedmann-Robertson-Walker models.

An interacting scalar field and the recent cosmic acceleration

“…So, the idea of varying ω is crucial here as it can very well serve the purpose of providing a signature flip in q in this interacting scenario. It deserves mention that the specific choice for the interaction in equation (8) and the choice of ω = ω(φ) in equation (12) are taken so as to yield the desired result. This is indeed a toy model which simply shows that investigations regarding an interaction amongst matter and the nonminimally coupled scalar field is worthwhile.…”

Time Dependent Cosmological Term and Holography

“…First of all, the holographic idea we have adopted to justify the EddingtonWeinberg relation is still just a conjecture, despite the several theoretical developments this subject has received in the last years [20]. On the other hand, the Friedmann equation (1) applied to this varying G context is something to be theoretically validated, for example in the realm of scalar-tensor theories [3,29]. It is possible to verify that our solutions, together with equation (1), are solutions of Brans-Dicke theories, and an exhaustive study about this will be shown elsewhere.…”

“…But why has m the order of the pion mass? The common belief is that a natural cutoff for the vacuum fluctuations should be given by the Planck mass m p = l (29) to (28) with m = m p , one obtains a Hubble radius of the order of l p , which is not consistent with our universe.…”

A Theoretical Study of the Cosmic Expansion in the Framework of Brans-Dicke Theory

“…Thus the BD theory or its modified versions have been shown to account for the present acceleration of universe [13,14]. An observation regarding the BD theory is that it can potentially generate sufficient acceleration in the matter dominated era even without taking into consideration an exotic quintessence field [15]. However, the researchers have been looking for a theory which can explain the change of cosmic expansion state from deceleration to acceleration.…”