%0 Journal Article
%T Scalar-Tensor Models of Normal and Phantom Dark Energy
%+ Laboratoire de Physique Théorique et Astroparticules (LPTA)
%A Gannouji, R.
%A Polarski, D.
%A Ranquet, A.
%A Starobinsky, A.A.
%Z 30 pages, 4 figures; Matches the published version containing an expanded discussion of various points
%< avec comité de lecture
%@ 1475-7508
%J Journal of Cosmology and Astroparticle Physics
%I Institute of Physics (IOP)
%V 0609
%P 016
%8 2006
%D 2006
%Z astro-ph/0606287
%R 10.1088/1475-7516/2006/09/016
%K dark energy theory
%K cosmological constant experiments
%K gravity
%Z Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]
%Z Physics [physics]/General Relativity and Quantum Cosmology [gr-qc]
%Z Physics [physics]/High Energy Physics - Theory [hep-th]Journal articles
%X We consider the viability of dark energy (DE) models in the framework of the scalar-tensor theory of gravity, including the possibility to have a phantom DE at small redshifts $z$ as admitted by supernova luminosity-distance data. For small $z$, the generic solution for these models is constructed in the form of a power series in $z$ without any approximation. Necessary constraints for DE to be phantom today and to cross the phantom divide line $p=-\rho$ at small $z$ are presented. Considering the Solar System constraints, we find for the post-Newtonian parameters that $\gamma_{PN}<1$ and $\gamma_{PN,0}\approx 1$ for the model to be viable, and $\beta_{PN,0}>1$ (but very close to 1) if the model has a significantly phantom DE today. However, prospects to establish the phantom behaviour of DE are much better with cosmological data than with Solar System experiments. Earlier obtained results for a $\Lambda$-dominated universe with the vanishing scalar field potential are extended to a more general DE equation of state confirming that the cosmological evolution of these models rule them out. Models of currently fantom DE which are viable for small $z$ can be easily constructed with a constant potential; however, they generically become singular at some higher $z$. With a growing potential, viable models exist up to an arbitrary high redshift.
%G English
%L in2p3-00115596
%U https://hal.in2p3.fr/in2p3-00115596
%~ IN2P3
%~ LPTA
%~ CNRS
%~ UNIV-MONTP2
%~ UNIV-MONTPELLIER
%~ UM1-UM2