paper

Cosmology with nonminimal kinetic coupling and a power-law potential

arXiv:1306.5090 · doi:10.1103/PhysRevD.88.083539

Abstract

We consider cosmological dynamics in the theory of gravity with the scalar field possessing a nonminimal kinetic coupling to gravity, , and the power-law potential . Using the dynamical system method, we analyze all possible asymptotical regimes of the model under investigation and show that for sloping potentials with there exists a quasi-de Sitter asymptotic corresponding to an early inflationary Universe. In contrast to the standard inflationary scenario, the kinetic coupling inflation does not depend on a scalar field potential and is only determined by the coupling parameter . We obtain that there exist two different late-time asymptotical regimes. The first one leads to the usual power-like cosmological evolution with , while the second one represents the late-time inflationary Universe with . This secondary inflationary phase depends only on and is a specific feature of the model with nonminimal kinetic coupling. Additionally, an asymptotical analysis shows that for the quadric potential with N=2 the asymptotical regimes remain qualitatively the same, while the kinetic coupling inflation is impossible for steep potentials with N>2. Using a numerical analysis, we also construct exact cosmological solutions and find initial conditions leading to the initial kinetic coupling inflation followed either by a "graceful" oscillatory exit or by the secondary inflation.

10 pages, 6 figures, submitted to PRD

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