Perturbation theorems for Hermitian elements in Banach algebras
Tom 134 / 1999
Studia Mathematica 134 (1999), 111-117
DOI: 10.4064/sm-134-2-111-117
Streszczenie
Two well-known theorems for Hermitian elements in C*-algebras are extended to Banach algebras. The first concerns the solution of the equation ax - xb = y, and the second gives sharp bounds for the distance between spectra of a and b when a, b are Hermitian.
