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Motohashi H.,University of Tokyo | Starobinsky A.A.,University of Tokyo | Starobinsky A.A.,Ld Landau Institute For Theoretical Physics Res | Yokoyama J.,University of Tokyo
Journal of Cosmology and Astroparticle Physics | Year: 2011

It is known that scalar-tensor theory of gravity admits regular crossing of the phantom divide line wDE = -1 for dark energy, and existing viable models of present dark energy for its particular case - f(R) gravity - possess one such crossing in the recent past, after the end of the matter dominated stage. It was recently noted that during the future evolution of these models the dark energy equation of state wDE may oscillate with an arbitrary number of phantom divide crossings. In this paper we prove that the number of crossings can be infinite, present an analytical condition for the existence of this effect and investigate it numerically. With the increase of the present mass of the scalaron (a scalar particle appearing in f(R) gravity) beyond the boundary of the appearance of such oscillations, their amplitude is shown to decrease very fast. As a result, the effect quickly becomes small and its beginning is shifted to the remote future. © 2011 IOP Publishing Ltd and SISSA.

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