Constraining scalar-tensor quintessence by cosmic clocks

¹ Dipartimento di Scienze Fisiche, Università di Napoli “Federico II”, Italy e-mail: capozziello@na.infn.it
² Istituto Nazionale di Fisica Nucleare, Sez. Napoli, via Cinthia, Compl. Univ. Monte S. Angelo, 80126 Naples, Italy
³ Department of Mathematics and Applied Mathematics, University of Cape Town and South African Astronomical Observatory, Observatory Cape Town, South Africa

Received: 9 May 2007
Accepted: 17 June 2007

Abstract

Aims.We study scalar tensor theories of gravity with power law scalar field potentials as cosmological models for accelerating universe, using cosmic clocks.

Methods.Scalar-tensor quintessence models can be constrained by identifying suitable cosmic clocks which allow one to select confidence regions for cosmological parameters. In particular, we constrain the characterizing parameters of non-minimally coupled scalar-tensor cosmological models which admit exact solutions of the Einstein field equations. Lookback time to galaxy clusters at low intermediate, and high redshifts is considered. The high redshift time-scale problem is also discussed in order to select other cosmic clocks such as quasars.

Results.The presented models seem to work in all the regimes considered: the main feature of this approach is the fact that cosmic clocks are completely independent of each other, so that, in principle, it is possible to avoid bias due to primary, secondary and so on indicators in the cosmic distance ladder.

Conclusions.We have used different methods to test cosmological models at low, intermediate and high redshift by different indicators: this seems to confirm independently these proposed dark energy models.