Statistical hierarchy of varying speed of light cosmologies
  Variation of the speed of light is quite a debated issue in cosmology with
some benefits, but also with some controversial concerns. Many approaches to
develop a consistent varying speed of light (VSL) theory have been developed
recently. Although a lot of theoretical debate has sprout out about their
feasibility and reliability, the most obvious and straightforward way to
discriminate and check if such theories are really workable has been missed out
or not fully employed. What is meant here is the comparison of these theories
with observational data in a fully comprehensive way. In this paper we try to
address this point i.e., by using the most updated cosmological probes, we test
three different candidates for a VSL theory (Barrow \& Magueijo, Avelino \&
Martins, and Moffat) signal. We consider many different ans\"{a}tze for both
the functional form of $c(z)$ (which cannot be fixed by theoretical
motivations) and for the dark energy dynamics, in order to have a clear global
picture from which we extract the results. We compare these results using a
reliable statistical tool such as the Bayesian Evidence. We find that the
present cosmological data is perfectly compatible with any of these VSL
scenarios, but in one case (Moffat model) we have a higher Bayesian Evidence
ratio in favour of VSL than in the standard $c=$ constant $\Lambda$CDM
scenario. Moreover, in such a scenario, the VSL signal can help to strengthen
constraints on the spatial curvature (with indication toward an open universe),
to clarify some properties of dark energy (exclusion of a cosmological constant
at $2\sigma$ level) and is also falsifiable in the nearest future due to some
peculiar issues which differentiate this model from the standard model.
Finally, we have applied some priors which come from cosmology and, in
particular, from information theory and gravitational thermodynamics.
