Subdifferentials with Autoconjugate Fitzpatrick Function

Abstract

In the framework of real Banach spaces, the present paper provides a necessary and sufficient condition for the Fitzpatrick function of the subdifferential of a proper lower semicontinuous convex function to be autoconjugate. This enables us to: obtain a new proof of the fact that subdifferentials of indicator and sublinear functions have autoconjugate Fitzpatrick functions; characterize those classes of functions whose subdifferentials fulfill the condition under study in the same special way as indicator and sublinear functions do; prove that, in the one-dimensional case, the functions of these classes are the only ones whose subdifferentials have autoconjugate Fitzpatrick functions, while this is not true in higher dimensions.