Accelerating universe in scalar tensor models – comparison of theoretical predictions with observations

¹ Institute for Theoretical Physics, University of Warsaw, Hoza 69, 00-681 Warsaw, Poland
² Department of Astronomy, Williams College, Williamstown, MA 01267, USA
³ Dipartimento di Scienze Fisiche, Università di Napoli Federico II, Compl. Univ. Monte S. Angelo, 80126 Naples, Italy e-mail: ester@na.infn.it
⁴ Istituto Nazionale di Fisica Nucleare, Sez. Napoli, via Cinthia, Compl. Univ. Monte S. Angelo, 80126 Naples, Italy

Received: 28 November 2005
Accepted: 13 March 2006

Abstract

Aims.To study the possibility of the appearance of an accelerated universe in scalar tensor cosmological models.

Methods.We consider scalar tensor theories of gravity assuming that the scalar field is not minimally coupled with gravity. We use this theory to study evolution of a flat homogeneous and isotropic universe. In this case the dynamical equations can be derived form a point-like Lagrangian. We study the general properties of dynamics of this system and show that for a wide range of initial conditions such models lead in a natural way to an accelerated phase of expansion of the universe. Assuming that the point-like Lagrangian admits a Noether symmetry, we are able to explicitly solve the dynamical equations.

Results.We study one particular model and show that its predictions are compatible with observational data, namely the publicly available data on type Ia supernovae, the parameters of large scale structure determined by the 2-degree Field Galaxy Redshift Survey (2dFGRS), the measurements of cosmological distances with the Sunyaev-Zel'dovich effect and the rate of growth of density perturbations. This model produces in a natural way an epoch of accelerated expansion. With an appropriate choice of parameters our model is fully compatible with several observed characteristics of the universe.