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Brans-Dicke Theory as a Unified Model for Dark Matter- Dark Energy

By Hongsu Kim

Abstract

The Brans-Dicke (BD) theory of gravity is taken as a possible theory of k-essence coupled to gravity. It then has been realized that the BD scalar field does indeed play a role of a k-essence, but in a very unique way which distinguishes it from other k-essence fields studied in the literature. That is, first in the BD scalar field-dominated era when the contribution from this k-essence overwhelms those from other types of matter, the BD theory predicts the emergence of a yet-unknown zero acceleration epoch which is an intermediate stage acting as a “crossing bridge” between the decelerating matter-dominated era and the accelerating phase. Upon realizing this, next, closer study of the effects of this k-essence on the evolutionary behavior of the matterdominated and the accelerating eras has been performed. The result of the study indicates that the BD scalar field appears to interpolate smoothly between these two late-time stages by speeding up the expansion rate of the matter-dominated era somewhat while slowing down that of the accelerating phase to some degree. Thus with the newly found BD scalar field-dominated era in between these two, the late-time of the universe evolution appears to be mixed sequence of the three stages

Year: 2005
OAI identifier: oai:CiteSeerX.psu:10.1.1.317.5043
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