Helson Beurling Teoremi ve Uygulamaları

Abstract

In thesis we treat the celebrated Helson-Beurling Theorem which charac- terizes the closed subspaces of L2 which are invariant under the shift operator. We also treat the characterization of invariant subspaces of the Volterra op- erator as an application of Helson-Beurling Theorem due to D. Sarason, char- acterization of multiplication and translation invariant subspaces of L2(R) as an application of Helson-Beurling theorem due to A. Katavolos and S. Power and characterization of multiplication and dilation invariant subspaces of L2(R) as an application of Helson-Beurling theorem due to A. Katavolos and S. Power.