On 2D Inverse Problems/ An infinite example

The following construction provides an example of an infinite graph, which Dirichlet-to-Neumann operator satisfies the operator equation in the title of this chapter. The operator equation reflects the self-duality and self-symmetry of the infinite graph. thumbnail|The self-dual and self-symmetric infinite graph Exercise (**). Prove that the Dirichlet-to-Neumann operator of the graph with the natural boundary satisfies the functional equation. (Hint) Use the fact that the operator/matrix is the fixed point of the Schur complement where is the circular matrix of first differences.