Green's function as a defect state in a boundary value problem

A perspective of the Green's function in a boundary value problem as only eigenstate an auxiliary formulation is introduced. In this treatment, can be perceived defect state presence $\ensuremath{\delta}$-function potential, height which depends on itself. This approach illustrated one-dimensional and two-dimensional Helmholtz equation problems, with emphasis systems that are open have non-Hermitian potential. We then draw analogy between obtained way chiral edge circumventing topological lattice, shines light local minimum at source position.