Convergent spectral inclusion sets for banded matrices

Abstract

AbstractWe obtain sequences of inclusion sets for the spectrum, essential spectrum, and pseudospectrum of banded, in general non‐normal, matrices of finite or infinite size. Each inclusion set is the union of the pseudospectra of certain submatrices of a chosen size n. Via the choice of n, one can balance accuracy of approximation against computational cost, and we show, in the case of infinite matrices, convergence as of the respective inclusion set to the corresponding spectral set.