  An unexpected distribution of temperatures in the CMB could be a sign of new
physics. In particular, the existence of cosmic defects could be indicated by
temperature discontinuities via the Kaiser-Stebbins effect. In this paper, we
show how performing finite differences on a CMB map, with the noise regularized
in harmonic space, may expose such discontinuities, and we report the results
of this process on the 7-year Wilkinson Microwave Anisotropy Probe data.
