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We use high-redshift type Ia supernova and compact radio source data in order to
test the infrared (IR) fixed point model of the late Universe which was proposed
recently. It describes a cosmology with a time dependent cosmological constant
and Newton constant whose dynamics arises from an underlying renormalization
group flow near an IR-attractive fixed point. Without any finetuning or
quintessence field it yields
. Its
characteristic - dependence of the scale factor leads to a
distance-redshift relation whose predictions are compared both to the supernova
and to the radio source data. According to the test, the fixed point
model reproduces the data at least as well as the best-fit
(Friedmann-Robertson-Walker) standard cosmology (see Fig.(1.23). Using
median statistics and a Bayesian model selection criterion we show that the
fixed point cosmology has even better chances of being the correct theory of
the late Universe than any standard cosmology. Furthermore, we extend the
original fixed point model by assuming that the fixed point epoch is preceded by
an era with constant and . By means of a Monte Carlo simulation we
show that the data expected from the forthcoming SNAP satellite mission could
detect the transition to the fixed point regime provided it took place at a
redshift of less than about ().

** Next:** Arnowittr-Deser-Misner gravity with variable
** Up:** Theoretical Cosmology
** Previous:** Cosmological Perturbations in Renormalization
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Innocenza Busa'
2005-11-14