Journal Home Page Cumulative Index List of all Volumes Complete Contentsof this Volume Previous Article Journal of Convex Analysis 16 (2009), No. 2, 409--421Copyright Heldermann Verlag 2009 Maximal Monotone Operators with a Unique Extension to the Bidual Maicon Marques Alves Instituto de Matemática Pura e Aplicada, Estrada Dona Castorina 110, Jardim Botânico, Rio de Janeiro, RJ 22460-320, Brazil maicon@impa.br Benar Fux Svaiter Instituto de Matemática Pura e Aplicada, Estrada Dona Castorina 110, Jardim Botânico, Rio de Janeiro, RJ 22460-320, Brazil benar@impa.br [Abstract-pdf] \newcommand{\tos}{\rightrightarrows} We study a sufficient condition under which a maximal monotone operator $T\colon X\tos X^*$ admits a unique maximal monotone extension to the bidual $\widetilde T\colon X^{**}\tos X^*$. We will prove that for non-linear operators this condition is equivalent to uniqueness of the extension. The central tool in our approach is the $\mathcal{S}$-function defined and studied previously by R. S. Burachik and B. F. Svaiter ["Maximal monotone operators, convex functions and a special family of enlargements", Set-Valued Analysis 10 (2002) 297--316]. For a generic operator, this function is the supremum of all convex lower semicontinuous functions which are majorized by the duality product in the graph of the operator.\par We also prove in this work that if the graph of a maximal monotone operator is convex, then this graph is an affine linear subspace. Keywords: Maximal monotone operators, extension, bidual, Banach spaces, Broendsted-Rockafellar property, S-function. MSC: 47H05, 49J52, 47N10 [ Fulltext-pdf  (137  KB)] for subscribers only.