Gamma-ray bursts as dark energy-matter probes in the context of the   generalized Chaplygin gas model
  In this paper we consider the use of Gamma Ray Bursts (GRBs) as distance markers to study the unification of dark energy and dark matter in the context of the so-called Generalized Chaplygin Gas (GCG) model. We consider that the GRB luminosity may be estimated from its variability, time-lag, and also use the so-called Ghirlanda relation. We evaluate the improvements one may expect once more GRBs and their redshift become available. We show that although GRBs allow for extending the Hubble diagram to higher redshifts, its use as a dark energy probe is limited when compared to SNe Ia. We find that the information from GRBs can provide some bounds on the amount of dark matter and dark energy independently of the equation of state. This is particularly evident for XCDM-type models, which are, for low-redshifts ($z\leq2$), degenerate with the GCG. 
O. Bertolami, P.T. Silva