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The General Iterative Methods for Asymptotically Nonexpansive Semigroups in Banach Spaces

DOI: 10.1155/2012/695183

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We introduce the general iterative methods for finding a common fixed point of asymptotically nonexpansive semigroups which is a unique solution of some variational inequalities. We prove the strong convergence theorems of such iterative scheme in a reflexive Banach space which admits a weakly continuous duality mapping. The main result extends various results existing in the current literature. 1. Introduction Let be a normed linear space. Let be a self-mapping on . Then is said to be asymptotically nonexpansive if there exists a sequence with such that for each , The class of asymptotically nonexpansive maps was introduced by Goebel and Kirk [1] as an important generalization of the class of nonexpansive maps (i.e., mappings such that , for all ). We use to denote the set of fixed points of , that is, . A self-mapping is a contraction on if there exists a constant such that We use to denote the collection of all contractions on . That is, ??is a contraction on?? . A family of mappings of into itself is called a strongly continuous semigroup of Lipschitzian mappings on if it satisfies the following conditions: (i) for all ; (ii) for all ; (iii)for each , there exists a bounded measurable function such that , for all?? ; (iv)for all , the mapping is continuous. A strongly continuous semigroup of Lipchitszian mappings is called strongly continuous semigroup of nonexpansive mappings if for all and strongly continuous semigroup of asymptotically nonexpansive if . Note that for asymptotically nonexpansive semigroup , we can always assume that the Lipchitszian constant is such that for each ,?? is nonincreasing in , and ; otherwise we replace , for each , with . We denote by the set of all common fixed points of , that is, is called uniformly asymptotically regular on [2, 3] if for all and any bounded subset of , and almost uniformly asymtotically regular on [4] if Let . Then, for each and for a nonexpansive map , there exists a unique point satisfying the following condition: since the mapping is a contraction. When is a Hilbert space and is a self-map, Browder [5] showed that converges strongly to an element of which is nearest to as . This result was extended to more various general Banach space by Morales and Jung [6], Takahashi and Ueda [7], Reich [8], and a host of other authors. Many authors (see, e.g., [9, 10]) have also shown the convergence of the path , in Banach spaces for asymptotically nonexpansive mapping self-map under some conditions on . It is an interesting problem to extend the above results to a strongly continuous semigroup of

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