Using H(z) data as a probe of the concordance model
  Direct observations of the Hubble rate, from cosmic chronometers and the
radial baryon acoustic oscillation scale, can out-perform supernovae
observations in understanding the expansion history, because supernovae
observations need to be differentiated to extract H(z). We use existing H(z)
data and smooth the data using a new Gaussian Processes package, GaPP, from
which we can also estimate derivatives. The obtained Hubble rate and its
derivatives are used to reconstruct the equation of state of dark energy and to
perform consistency tests of the LCDM model, some of which are newly devised
here. Current data is consistent with the concordance model, but is rather
sparse. Future observations will provide a dramatic improvement in our ability
to constrain or refute the concordance model of cosmology. We produce simulated
data to illustrate how effective H(z) data will be in combination with Gaussian
Processes.
