Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8899656 | Journal of Mathematical Analysis and Applications | 2018 | 25 Pages |
Abstract
Let A be a complex unital Banach algebra, aâA, nâZ+ and ϵ>0. The (n,ϵ)-pseudospectrum În,ϵ(a) of a is defined asÎn,ϵ(a):=Ï(a)âª{λâÏ(a):â(λâa)â2nâ1/2nâ¥1ϵ}. Here Ï(a) denotes the spectrum of a. The usual pseudospectrum Îϵ(a) of a is a special case of this, namely Î0,ϵ(a). It is proved that (n,ϵ)-pseudospectrum approximates the closed ϵ-neighbourhood of spectrum for large n. Further, it has been shown that (n,ϵ)-pseudospectrum has no isolated points, has a finite number of connected components and each component contains an element from Ï(a). Some examples are given to illustrate these results.
Keywords
Related Topics
Physical Sciences and Engineering
Mathematics
Analysis
Authors
Kousik Dhara, S.H. Kulkarni,