The complementarity of the redshift drift
  We derive some basic equations related to the redshift drift and we show how
some dark energy (DE) properties can be retrieved from it. We consider in
particular three kinds of DE models which exhibit a characteristic signature in
their redshift drift while no such signature would be present in their
luminosity-distances: a sudden change of the equation of state parameter w_{DE}
at low redshifts, oscillating DE and finally an equation of state with spikes
at low redshifts. Accurate redshift drift measurements would provide
interesting complementary probes for some of these models and for models with
varying gravitational coupling. While the redshift drift would efficiently
constrain models with a spike at z~1, the signature of the redshift drift for
models with large variations at very low redshifts z<0.1 would be unobservable,
allowing a large arbitrariness in the present expansion of the universe.
