Spectra of infinite graphs: two methods of computation

Leonid Golinskii

Published 2020-01-23Version 1

Two method for computation of the spectra of certain infinite graphs are suggested. The first one can be viewed as a reversed Gram--Schmidt orthogonalization procedure. It relies heavily on the spectral theory of Jacobi matrices. The second method is related to the Schur complement for block matrices. A number of examples including infinite graphs with tails, chains of cycles and ladders are worked out in detail.