The functional calculus for normal elements in -algebras is an important tool of analysis. We suggest an approximate substitute for such calculus for elements with the small self-commutator norm . We show that many properties of the functional calculus are conserved up to order .
Cite this article
Nikolai D. Filonov, Ilya Kachkovskiy, Polynomials of almost normal arguments in -algebras. J. Spectr. Theory 2 (2012), no. 4, pp. 355–371