A Dual Criterion for Maximal Monotonicity of Composition Operators

Abstract

In this paper we present a dual criterion for the maximal monotonicity of the composition operator \(T:=A^{\ast }SA\), where \(S:Y\rightrightarrows Y^{\,{\prime }}\) is a maximal monotone (set-valued) operator and \(A: X\rightarrow Y\) is a continuous linear map with the adjoint \(A^{\ast }\), \(X\) and \(Y\) are reflexive Banach spaces, and the product notation indicates composition. The dual criterion is expressed in terms of the closure condition involving the epigraph of the conjugate of Fitzpatrick function associated with \(S\), and the operator \(A.\) As an easy application, a dual criterion for the maximality of the sum of two maximal monotone operators is also given.