Is the Cosmic Transparency Spatially Homogeneous?
  We study the constraints on the cosmic opacity using the latest BAO and
Union2 SNIa data in this paper and find that the best fit values seem to
indicate that an opaque universe is preferred in redshift regions $0.20-0.35$,
$0.35-0.44$ and $0.60-0.73$, whereas, a transparent universe is favored in
redshift regions $0.106-0.20$, $0.44-0.57$and $0.57-0.60$. However, our result
is still consistent with a transparent universe at the 1$\sigma$ confidence
level, even though the best-fit cosmic opacity oscillates between zero and some
nonzero values as the redshift varies.
