Minimal Gerschgorin sets. II

On a problem of O. Taussky

“…Taussky [5, p. 129] has an immediate answer in terms of the results of [3]. In [3], the authors completely characterized the spectrum S(Ω σ ) of a related set Ω o of matrices, where C = (c itj ) was an arbitrary n x 7i complex matrix and (1.…”

“…In [3], the authors completely characterized the spectrum S(Ω σ ) of a related set Ω o of matrices, where C = (c itj ) was an arbitrary n x 7i complex matrix and (1. (1)(2)(3)(4) S(Ω A ) = U S(Ω Λmθ) ) .…”

“…In the general case when A is not essentially diagonally dominant, we must use permutations and intersections (Theorem 3) to fully o describe S(Ω Λ ), in the spirit of [3]. These results are described in § 3.…”

Convexity and Minimal Gerschgorin Sets

“…The problem of how to determine all eigenvalues of matrices in Ua was solved by R. S. Varga and the author [6], [4] by the introduction of minimal Gerschgorin sets, G*(Q^), to be defined in §3.…”

“…In this note, we give a new derivation of the main results of [4] using a lemma of V. Klee on convex sets [3].…”