Model-independent constraints on the cosmic opacity
  We use current measurements of the expansion rate $H(z)$ and cosmic
background radiation bounds on the spatial curvature of the Universe to impose
cosmological model-independent constraints on cosmic opacity. To perform our
analyses, we compare opacity-free distance modulus from $H(z)$ data with those
from two supernovae Ia compilations: the Union2.1 plus the most distant
spectroscopically confirmed SNe Ia (SNe Ia SCP-0401 $z=1.713$) and two Sloan
Digital Sky Survey (SDSS) subsamples. The influence of different SNe Ia
light-curve fitters (SALT2 and MLCS2K2) on the results is also verified. We
find that a completely transparent universe is in agreement with the largest
sample in our analysis (Union 2.1 plus SNe Ia SCP-0401). For SDSS sample a such
universe it is compatible at $< 1.5\sigma$ level regardless the SNe Ia
light-curve fitting used.
