Study of Composition Operators in Certain Functional Spaces

Abstract

In this thesis we study three problems. The first is the superposition of the operators and their proprities, such as boundedness,continuity,regularity and the inequalities of the norms of the composition of functions in some functional spaces. The second is to generalize some results of the composition of more than two functions, and the third is to give a generalization of Peetre's theorem.