3 research outputs found
The growth of matter perturbations in some scalar-tensor DE models
We consider asymptotically stable scalar-tensor dark energy (DE) models for
which the equation of state parameter tends to zero in the past. The
viable models are of the phantom type today, however this phantomness is milder
than in General Relativity if we take into account the varying gravitational
constant when dealing with the SNIa data. We study further the growth of matter
perturbations and we find a scaling behaviour on large redshifts which could
provide an important constraint. In particular the growth of matter
perturbations on large redshifts in our scalar-tensor models is close to the
standard behaviour , while it is substantially different
for the best-fit model in General Relativity for the same parametrization of
the background expansion. As for the growth of matter perturbations on small
redshifts, we show that in these models the parameter can take absolute values much larger than in models inside
General Relativity. Assuming a constant when is large
would lead to a poor fit of the growth function . This provides another
characteristic discriminative signature for these models.Comment: 13 pages, 7 figures, matches version published in JCA
The accelerating universe and a limiting curvature proposal
We consider the hypothesis of a limiting minimal curvature in gravity as a
way to construct a class of theories exhibiting late-time cosmic acceleration.
Guided by the minimal curvature conjecture (MCC) we are naturally lead to a set
of scalar tensor theories in which the scalar is non-minimally coupled both to
gravity and to the matter Lagrangian. The model is compared to the Lambda Cold
Dark Matter concordance model and to the observational data using the gold
SNeIa sample of Riess et. al. (2004). An excellent fit to the data is achieved.
We present a toy model designed to demonstrate that such a new, possibly
fundamental, principle may be responsible for the recent period of cosmological
acceleration. Observational constraints remain to be imposed on these models.Comment: 22 pages, 7 figures; revised version to appear in JCAP; references
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