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Required Conditions for Late Time Acceleration and Early Time Deceleration in Generalized Scalar-Tensor Theories | | L. M. Diaz-Rivera
; Luis O. Pimentel
; | | Date: |
21 Aug 2002 | | Journal: | Int.J.Mod.Phys. A18 (2003) 651-672 | | Subject: | gr-qc | | Abstract: | We consider a generalized scalar-tensor theory, where we let the coupling function $omega(phi)$ and the effective cosmological constants $Lambda(phi)$ undetermined. We obtain general expressions for $omega(phi)$ and $Lambda(phi)$ in terms of the scalar field and the scale factor, and show that $omega(phi)$ depends on the scalar field and the scale factor in a complicated way. In order to study the conditions for an accelerated expansion at the present time and a decelerated expansion in the past, we assume a power law evolution for the scalar field and the scale factor. We analyse the required conditions that allow our model to satisfy the weak field limits on $omega(phi)$, and at the same time, to obtain the correct values of cosmological parameters, as the energy density $ Omega_{m0}$ and cosmological constant $Lambda(t_0)$. We also study the conditions for a decelerated expansion at an early time dominated by radiation. We find values for $omega(phi)$ and $Lambda(phi)$ consistent with the expectations of a theory where the cosmological constant decreases with the time and the coupling function increases until the values accepted today. | | Source: | arXiv, gr-qc/0208061 | | Services: | Forum | Review | PDF | Favorites | |
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