What is needed of a tachyon if it is to be the dark energy?

Edmund J. Copeland; Mohammad R. Garousi; M. Sami; Shinji Tsujikawa

doi:10.1103/PhysRevD.71.043003

paper

What is needed of a tachyon if it is to be the dark energy?

arXiv:hep-th/0411192 · doi:10.1103/PhysRevD.71.043003

Abstract

We study a dark energy scenario in the presence of a tachyon field $ϕ$ with potential $V (ϕ)$ and a barotropic perfect fluid. The cosmological dynamics crucially depends on the asymptotic behavior of the quantity $λ = - M_{p} V_{ϕ} / V^{3/2}$ . If $λ$ is a constant, which corresponds to an inverse square potential $V (ϕ) \propto ϕ^{- 2}$ , there exists one stable critical point that gives an acceleration of the universe at late times. When $λ \to 0$ asymptotically, we can have a viable dark energy scenario in which the system approaches an ``instantaneous'' critical point that dynamically changes with $λ$ . If $∣ λ ∣$ approaches infinity asymptotically, the universe does not exhibit an acceleration at late times. In this case, however, we find an interesting possibility that a transient acceleration occurs in a regime where $∣ λ ∣$ is smaller than of order unity.

arXiv comment11 pages and 3 figures, minor clarifications added; final version to appear in PRD

What is needed of a tachyon if it is to be the dark energy?

Abstract

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