  An important characteristic of topological band insulators is the necessary
presence of in-gap edge states on the sample boundary. We utilize this fact to
show that when the boundary is reconnected with a twist, there are always
zero-energy defect states. This provides a natural connection between novel
defects in the two-dimensional $p_{x}+ip_{y}$ superconductor, the Kitaev model,
the fractional quantum Hall effect, and the one-dimensional domain wall of
polyacetylene.

Strongly Correlated Electrons;Mesoscale and Nanoscale Physics