Operators and Matrices · Volume 11, Issue 1 Pseudospectrum of an element of a Banach algebra 11-18 Pages 263-287 DOI 10.7153/oam-11-18 Downloads Short PDF Full PDF PNG Authors Arundhathi Krishnan S. H. Kulkarni Keywords Banach algebra Hermitian idempotent numerical range pseudospectrum semisimple spectrum Subject classes 47A10 46H05 47A12