TY - JOUR

T1 - Scalar-tensor models of normal and phantom dark energy

AU - Gannouji, Radouane

AU - Polarski, David

AU - Ranquet, André

AU - Starobinsky, Alexei A.

PY - 2006/9/1

Y1 - 2006/9/1

N2 - We consider the viability of dark energy (DE) models in the framework of the scalar-tensor theory of gravity, including the possibility of having 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 = -ρ at small z are presented. Considering the solar system constraints, we find for the post-Newtonian parameters that γPN < 1 and γPN,0 ≈ 1 for the model to be viable, and βPN,0 > 1 (but very close to 1) if the model has a significantly phantom DE today. However, prospects for establishing the phantom behaviour of DE are much better with cosmological data than with solar system experiments. Earlier obtained results for a Λ-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 rules them out. Models of currently phantom 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.

AB - We consider the viability of dark energy (DE) models in the framework of the scalar-tensor theory of gravity, including the possibility of having 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 = -ρ at small z are presented. Considering the solar system constraints, we find for the post-Newtonian parameters that γPN < 1 and γPN,0 ≈ 1 for the model to be viable, and βPN,0 > 1 (but very close to 1) if the model has a significantly phantom DE today. However, prospects for establishing the phantom behaviour of DE are much better with cosmological data than with solar system experiments. Earlier obtained results for a Λ-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 rules them out. Models of currently phantom 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.

KW - Cosmological constant experiments

KW - Dark energy theory

KW - Gravity

UR - http://www.scopus.com/inward/record.url?scp=37649031001&partnerID=8YFLogxK

U2 - 10.1088/1475-7516/2006/09/016

DO - 10.1088/1475-7516/2006/09/016

M3 - Article

AN - SCOPUS:37649031001

SN - 1475-7516

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

IS - 9

M1 - 016

ER -