The role of potential in the ghost-condensate dark energy model

Abstract

We consider the ghost-condensate model of dark energy with a generic potential term. The inclusion of the potential is shown to give greater freedom in realising the phantom regime. The self-consistency of the analysis is demonstrated using WMAP7 + BAO + Hubble data.

Energy momentum tensor of a non-minimally coupled scalar from the equivalence of the Einstein and Jordan frames

“…The widespread use of scalar-tensor theories [8][9][10][11][12] in cosmology demands a close examination of the ambiguity that is present in the energy momentum tensor (EMT) of the non-minimally coupled scalar. This is owing to the non-minimal nature of it's coupling with gravity in the action which renders a direct application of the standard definition of symmetric EMT unsuitable in such theories.…”

“…The Brans-Dicke type of coupling has gained popularity in recent past, because observational evidence in favour of the late time cosmic acceleration has opened up possibilities for such alternatives. These are called scalar-tensor theories [8][9][10][11][12] and they are adopted as modified theories of gravity in numerous investigations [13]. The energy momentum tensor (EMT) of the scalar field in these scalar-tensor theories can not be obtained using the standard definition of symmetric EMT [2] that applies to minimally coupled scalar field models because the action in such theories contain terms that can not be classified either into purely gravitational or non-gravitational sectors [14].…”

Vacuum polarization in Siklos spacetimes

“…They also applied the formulation to gravitational wave spacetime (in the weak-field approximation) and also to the Schwarzschild spacetime and the superluminalsubluminal motion and also birefringence were shown explicitly. Their theory has then been examined in several spacetimes; namely in Reissner-Nordstrum spacetime in [2], in Kerr spacetime in [3], in dilaton black hole spacetimes in [4], in the static and rotating topological back hole backgrounds in [5], and more recently in [6], in which by considering the Kerr-de Sitter and static de Sitter cosmic string spacetimes, the effect of a positive cosmological canstant was studied. Other aspects of this theory have been discussed in the literature, including generalization to high frequency limit and discussion of various kinds of velocity in [7], the issue of causality violation in [8,9], and the problem of superluminality in [10].…”

Galileons, phantom fields, and the fate of the Universe

“…Following this, a special class of dark energy models based on the large scale modification of gravity called Galileon gravity [66][67][68][69][70][71][72][73][74][75][76][77][78][79] was proposed. The distinguishing feature of this theory is that it provides a consistent modification of general relativity leaving the local physics intact.…”