TY - JOUR

T1 - String-inspired cosmology

T2 - A late time transition from a scaling matter era to a dark energy universe caused by a Gauss-Bonnet coupling

AU - Tsujikawa, Shinji

AU - Sami, M.

PY - 2007/1/1

Y1 - 2007/1/1

N2 - The Gauss-Bonnet (GB) curvature invariant coupled to a scalar field can lead to an exit from a scaling matter dominated epoch to a late time accelerated expansion, which is attractive for alleviating the coincidence problem of dark energy. We derive the condition for the existence of cosmological scaling solutions in the presence of the GB coupling for a general scalar field Lagrangian density p(,X), where X ≤ -(1/2)(∇φ)2 is a kinetic term of the scalar field. The GB coupling and the Lagrangian density are restricted to being in the forms f(φ) eλφ and p ≤ Xg(Xeλ), respectively, where λ is a constant and g is an arbitrary function. We also derive fixed points for such a scaling Lagrangian with a GB coupling f(φ) eμφ and clarify the conditions under which the scaling matter era is followed by a de Sitter solution which can appear in the presence of the GB coupling. Among the scaling models proposed in the current literature, we find that the models which allow such a cosmological evolution are an ordinary scalar field with an exponential potential and a tachyon field with an inverse square potential, although the latter requires a coupling between dark energy and dark matter.

AB - The Gauss-Bonnet (GB) curvature invariant coupled to a scalar field can lead to an exit from a scaling matter dominated epoch to a late time accelerated expansion, which is attractive for alleviating the coincidence problem of dark energy. We derive the condition for the existence of cosmological scaling solutions in the presence of the GB coupling for a general scalar field Lagrangian density p(,X), where X ≤ -(1/2)(∇φ)2 is a kinetic term of the scalar field. The GB coupling and the Lagrangian density are restricted to being in the forms f(φ) eλφ and p ≤ Xg(Xeλ), respectively, where λ is a constant and g is an arbitrary function. We also derive fixed points for such a scaling Lagrangian with a GB coupling f(φ) eμφ and clarify the conditions under which the scaling matter era is followed by a de Sitter solution which can appear in the presence of the GB coupling. Among the scaling models proposed in the current literature, we find that the models which allow such a cosmological evolution are an ordinary scalar field with an exponential potential and a tachyon field with an inverse square potential, although the latter requires a coupling between dark energy and dark matter.

KW - Cosmological applications of theories with extra dimensions

KW - String theory and cosmology

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U2 - 10.1088/1475-7516/2007/01/006

DO - 10.1088/1475-7516/2007/01/006

M3 - Article

AN - SCOPUS:42749099918

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

SN - 1475-7516

IS - 1

M1 - 006

ER -