Properties and computations of matrix pseudospectra

摘要

Pseudospectra were introduced as early as 1975 [J. Analyse Math. 28 (1975) 335] and became popular tool during the 1990s. In this paper, we give a new definition of pseudospectra by using QR decomposition. Some properties of pseudospectra are explored and an algorithm for the computation of pseudospectra is given.