(1) Departamento de Matematicas, CINVESTAV del I.P.N, Apartado Postal 14-740, 07000 Mexico, D.F., Mexico;(2) Department of Mathematics, King‘s College London, Strand, London, WC2R 2LS, UK
Abstract:
We discuss the optimality of a sufficient condition from [12] for a point to belong to the essential spectrum of a Toeplitz operator with a bounded measurable coefficient. Our approach is based on a new sufficient condition for a composition of a Muckenhoupt weight with a Blaschke product to belong to the same Muckenhoupt class. The first author was partially supported by CONACYT project U46936-F, Mexico.