The Bulk-Edge Correspondence in Three Simple Cases

We present examples in three symmetry classes of topological insulators in one or two dimensions where the proof of the bulk-edge correspondence is particularly simple. This serves to illustrate the mechanism behind the bulk-edge principle without the overhead of the more general proofs which are available. We also give a new formula for the $\mathbb{Z}$_{2}-index of our time-reversal invariant systems inspired by Moore and Balents.