Holographic dark energy in Brans-Dicke theory with logarithmic form of scalar field

C P Singh; Pankaj Kumar

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arXiv · 1609.01477

Holographic dark energy in Brans-Dicke theory with logarithmic form of scalar field

C P Singh·Pankaj Kumar

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Abstract

In this paper, an interacting holographic dark energy model with Hubble horizon as an infra-red cut-off is considered in the framework of Brans-Dicke theory. We propose a logarithmic form $\phi \propto ln(\alpha+\beta a)$ of the Brans-Dicke scalar field to alleviate the problems of interacting holographic dark energy models in Brans-Dicke theory. We find that the equation of state parameter $w_h$ and deceleration parameter $q$ are negative in the early time which shows the early time inflation. During the evolution the sign of parameter $q$ changes from negative to positive which means that the Universe expands with decelerated rate whereas the sign of $w_h$ may change or remain negative throughout the evolution depending on the values of parameters. It is also observed that $w_h$ may cross the phantom divide line in the late time evolution. The sign of $q$ changes from positive to negative during late time of evolution which explains the late time accelerated expansion of the Universe. Thus, we present a unified model of holographic dark energy which explains the early time acceleration (inflation), medieval time deceleration and late time acceleration. We also discuss the cosmic coincidence problem. We obtain a time-varying density ratio of holographic dark energy to dark matter which is a constant of order one ($r\sim \mathcal{O}(1)$) during early and late time evolution. Therefore, our model successfully resolves the cosmic coincidence problem.

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BibTeX RIS

C P Singh, Pankaj Kumar. 2016-09-06. Holographic dark energy in Brans-Dicke theory with logarithmic form of scalar field. https://arxiv.org/abs/1609.01477

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