TY - JOUR
T1 - What is needed of a tachyon if it is to be the dark energy?
AU - Copeland, Edmund J.
AU - Garousi, Mohammad R.
AU - Sami, M.
AU - Tsujikawa, Shinji
PY - 2005/2
Y1 - 2005/2
N2 - 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.
AB - 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.
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U2 - 10.1103/PhysRevD.71.043003
DO - 10.1103/PhysRevD.71.043003
M3 - Article
AN - SCOPUS:84875008906
VL - 71
SP - 043003-1-043003-11
JO - Physical Review D - Particles, Fields, Gravitation and Cosmology
JF - Physical Review D - Particles, Fields, Gravitation and Cosmology
SN - 1550-7998
IS - 4
M1 - 043003
ER -