Let be a real locally uniformly convex reflexive Banach space with locally uniformly convex dual space * . Let : ⊇ ( ) → 2 * and : ⊇ ( ) → 2 * be maximal monotone operators. The maximality of the sum of two maximal monotone operators has been an open problem for many years. In this paper, new maximality theorems are proved for + under weaker sufficient conditions. These theorems improved the well-known maximality results of Rockafellar who used condition ∘ ( ) ∩ ( ) ̸ = 0 and Browder and Hess who used the quasiboundedness of and condition 0 ∈ ( ) ∩ ( ). In particular, the maximality of + is proved provided that ∘ ( ) ∩ ( ) ̸ = 0, where : → (−∞, ∞] is a proper, convex, and lower semicontinuous function. Consequently, an existence theorem is proved addressing solvability of evolution type variational inequality problem for pseudomonotone perturbation of maximal monotone operator.
PreliminariesIn what follows, the norm of spaces and * will be denoted by ‖ ⋅ ‖. For ∈ and * ∈ * , pairing ⟨ * , ⟩ denotes value * ( ). Let and be real Banach spaces. For operator : → 2 , we define domain ( ) of by ( ) = { ∈ : ̸ = 0} and range ( ) of by ( ) = ⋃ ∈ ( ) . We also use symbol ( ) for the graph of : ( ) = {( , * ) : ∈ ( ), * ∈ }. A single-valued operator : ⊃ ( ) → is "demicontinuous," if it is continuous from the strong topology of ( ) to the weak topology of . It is "compact," if it is strongly continuous and maps bounded subsets of ( ) to relatively compact subsets of . A multivalued operator : ⊃ ( ) → 2 is "bounded," if it maps each bounded subset of ( ) into a bounded subset of . It is "finitely continuous," if it is upper semicontinuous from each finite dimensional subspace of to the weak topology of . Throughout the paper, we use notations ⇀ 0 and → 0 in to denote the weak and strong convergence of sequence { }, respectively. Analogous notations are used for convergence of a sequence in * . Let : [0, ∞) → (−∞, ∞) be a continuous and strictly increasing function such that ( ) → ∞ as → ∞. The mapping : → 2 * defined byis called the "generalized duality mapping" associated with . If ( ) = for all ≥ 0, is denoted by and is called "the normalized duality mapping." As a consequence of the Hahn-Banach theorem, it is well-known that ( ) ̸ = 0 for all ∈ . Since and * are locally uniformly convex, is single valued, bounded, monotone, and bicontinuous. Definition 1. An operator : ⊃ ( ) → 2 * is said to be (i) "monotone" if for every ∈ ( ), ∈ ( ), * ∈ , and V * ∈ , one has ⟨ * − V * , − ⟩ ≥ 0;(ii) "maximal monotone" if is monotone and ( + ) = * for every > 0; that is, is maximal monotone if and only if is monotone and then ( , * ) ∈ and ⟨ * , ⟩ → ⟨ * , ⟩ as → ∞.
Browder and Hess [2] introduced the following definitions. The original definition of single valued pseudomonotone operator is due to Brézis [3].Definition 3. An operator : ⊃ ( ) → 2 * is said to be "pseudomonotone" if the following conditions are satisfied:is nonempty, closed, convex, and bounded subset of * .(ii) is finitely continuous; that is, for every 0 ∈ ( )∩ and every...