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 = -MpVφ/V3/2. die;/í3/É2. If λ is a constant, which corresponds to an inverse square potential V(φ) ∝ φ-2, there exists one stable critical point that gives an acceleration of the Universe at late times. When λ → 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.
|ジャーナル||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|出版ステータス||Published - 2005 2|
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