Abstract

The propose of this paper is to present a modified block iterative algorithm for finding a common element between the set of solutions of the fixed points of two countable families of asymptotically relatively nonexpansive mappings and the set of solution of the system of generalized mixed equilibrium problems in a uniformly smooth and uniformly convex Banach space. Our results extend many known recent results in the literature.

1. Introduction

The equilibrium problem theory provides a novel and unified treatment of a wide class of problems which arise in economics, finance, image reconstruction, ecology, transportation, networks, elasticity, and optimization, and it has been extended and generalized in many directions.

In the theory of equilibrium problems, the development of an efficient and implementable iterative algorithm is interesting and important. This theory combines theoretical and algorithmic advances with novel domain of applications. Analysis of these problems requires a blend of techniques from convex analysis, functional analysis, and numerical analysis.

Let ๐ธ be a Banach space with norm โ€–โ‹…โ€–, ๐ถ be a nonempty closed convex subset of ๐ธ, and let ๐ธโˆ— denote the dual of ๐ธ. Let ๐‘“๐‘–โˆถ๐ถร—๐ถโ†’โ„ be a bifunction, ๐œ“๐‘–โˆถ๐ถโ†’โ„ be a real-valued function, where โ„ is denoted by the set of real numbers, and ๐ด๐‘–โˆถ๐ถโ†’๐ธโˆ— be a nonlinear mapping. The goal of the system of generalized mixed equilibrium problem is to find ๐‘ขโˆˆ๐ถ such that ๐‘“1(๐‘ข,๐‘ฆ)+โŸจ๐ด1๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐œ“1(๐‘ฆ)โˆ’๐œ“1๐‘“(๐‘ข)โ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ,2(๐‘ข,๐‘ฆ)+โŸจ๐ด2๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐œ“2(๐‘ฆ)โˆ’๐œ“2โ‹ฎ๐‘“(๐‘ข)โ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ,๐‘(๐‘ข,๐‘ฆ)+โŸจ๐ด๐‘๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐œ“๐‘(๐‘ฆ)โˆ’๐œ“๐‘(๐‘ข)โ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ.(1.1) If ๐‘“๐‘–=๐‘“, ๐ด๐‘–=๐ด, and ๐œ“๐‘–=๐œ“, the problem (1.1) is reduced to the generalized mixed equilibrium problem, denoted by GEMP(๐‘“,๐ด,๐œ“), to find ๐‘ขโˆˆ๐ถ such that ๐‘“(๐‘ข,๐‘ฆ)+โŸจ๐ด๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐œ“(๐‘ฆ)โˆ’๐œ“(๐‘ข)โ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ.(1.2) The set of solutions to (1.2) is denoted by ฮฉ, that is, ฮฉ={๐‘ฅโˆˆ๐ถโˆถ๐‘“(๐‘ข,๐‘ฆ)+โŸจ๐ด๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐œ‘(๐‘ฆ)โˆ’๐œ‘(๐‘ข)โ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ}.(1.3) If ๐ด=0, the problem (1.2) is reduced to the mixed equilibrium problem for ๐‘“, denoted by MEP(๐‘“,๐œ“), to find ๐‘ขโˆˆ๐ถ such that ๐‘“(๐‘ข,๐‘ฆ)+๐œ“(๐‘ฆ)โˆ’๐œ“(๐‘ข)โ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ.(1.4) If ๐‘“โ‰ก0, the problem (1.2) is reduced to the mixed variational inequality of Browder type, denoted by VI(๐ถ,๐ด,๐œ“), is to find ๐‘ขโˆˆ๐ถ such that โŸจ๐ด๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐œ“(๐‘ฆ)โˆ’๐œ“(๐‘ข)โ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ.(1.5) If ๐ด=0 and ๐œ“=0, the problem (1.2) is reduced to the equilibrium problem for ๐‘“, denoted by EP(๐‘“), to find ๐‘ขโˆˆ๐ถ such that ๐‘“(๐‘ข,๐‘ฆ)โ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ.(1.6)

The above formulation (1.6) was shown in [1] to cover monotone inclusion problems, saddle-point problems, variational inequality problems, minimization problems, vector equilibrium problems, and Nash equilibria in noncooperative games. In addition, there are several other problems, for example, the complementarity problem, fixed-point problem, and optimization problem, which can also be written in the form of an EP(๐‘“). In other words, the EP(๐‘“) is a unifying model for several problems arising in physics, engineering, science, economics, and so forth. In the last two decades, many papers have appeared in the literature on the existence of solutions to EP(๐‘“); see, for example [1โ€“4] and references therein. Some solution methods have been proposed to solve the EP(๐‘“); see, for example, [2, 4โ€“15] and references therein. In 2005, Combettes and Hirstoaga [5] introduced an iterative scheme of finding the best approximation to the initial data when EP(๐‘“) is nonempty, and they also proved a strong convergence theorem.

A Banach space ๐ธ is said to be strictly convex if โ€–(๐‘ฅ+๐‘ฆ)/2โ€–<1 for all ๐‘ฅ,๐‘ฆโˆˆ๐ธ with โ€–๐‘ฅโ€–=โ€–๐‘ฆโ€–=1 and ๐‘ฅโ‰ ๐‘ฆ. Let ๐‘ˆ={๐‘ฅโˆˆ๐ธโˆถโ€–๐‘ฅโ€–=1} be the unit sphere of ๐ธ. Then the Banach space ๐ธ is said to be smooth, provided lim๐‘กโ†’0โ€–๐‘ฅ+๐‘ก๐‘ฆโ€–โˆ’โ€–๐‘ฅโ€–๐‘ก(1.7) exists for each ๐‘ฅ,๐‘ฆโˆˆ๐‘ˆ. It is also said to be uniformly smooth if the limit is attained uniformly for ๐‘ฅ,๐‘ฆโˆˆ๐ธ. The modulus of convexity of ๐ธ is the function ๐›ฟโˆถ[0,2]โ†’[0,1] defined by ๎‚†โ€–โ€–โ€–๐›ฟ(๐œ€)=inf1โˆ’๐‘ฅ+๐‘ฆ2โ€–โ€–โ€–๎‚‡.โˆถ๐‘ฅ,๐‘ฆโˆˆ๐ธ,โ€–๐‘ฅโ€–=โ€–๐‘ฆโ€–=1,โ€–๐‘ฅโˆ’๐‘ฆโ€–โ‰ฅ๐œ€(1.8) A Banach space ๐ธ is uniformly convex, if and only if ๐›ฟ(๐œ€)>0 for all ๐œ€โˆˆ(0,2].

Let ๐ธ be a Banach space, ๐ถ be a closed convex subset of ๐ธ, a mapping ๐‘‡โˆถ๐ถโ†’๐ถ is said to be nonexpansive if โ€–๐‘‡๐‘ฅโˆ’๐‘‡๐‘ฆโ€–โ‰คโ€–๐‘ฅโˆ’๐‘ฆโ€–(1.9) for all ๐‘ฅ,๐‘ฆโˆˆ๐ถ. We denote by ๐น(๐‘‡) the set of fixed points of ๐‘‡. If ๐ถ is a bounded closed convex set and ๐‘‡ is a nonexpansive mapping of ๐ถ into itself, then ๐น(๐‘‡) is nonempty (see [16]). A point ๐‘ in ๐ถ is said to be an asymptotic fixed point of ๐‘‡ [17] if ๐ถ contains a sequence {๐‘ฅ๐‘›} which converges weakly to ๐‘ such that lim๐‘›โ†’โˆžโ€–๐‘ฅ๐‘›โˆ’๐‘‡๐‘ฅ๐‘›โ€–=0. The set of asymptotic fixed points of ๐‘‡ will be denoted byโ€‰โ€‰๎ƒ€๐น(๐‘‡). A point ๐‘โˆˆ๐ถ is said to be a strong asymptotic fixed point of ๐‘‡, if there exists a sequence {๐‘ฅ๐‘›}โŠ‚๐ถ such that ๐‘ฅ๐‘›โ†’๐‘ and โ€–๐‘ฅ๐‘›โˆ’๐‘‡๐‘ฅ๐‘›โ€–โ†’0. The set of strong asymptotic fixed points of ๐‘‡ will be denoted by ๎๐น(๐‘‡). A mapping ๐‘‡ from ๐ถ into itself is said to be relatively nonexpansive [18โ€“20] if ๎ƒ€๐น(๐‘‡)=๐น(๐‘‡) and ๐œ™(๐‘,๐‘‡๐‘ฅ)โ‰ค๐œ™(๐‘,๐‘ฅ) for all ๐‘ฅโˆˆ๐ถ and ๐‘โˆˆ๐น(๐‘‡). The asymptotic behavior of a relatively nonexpansive mapping was studied in [21, 22]. ๐‘‡ is said to be ๐œ™-nonexpansive, if ๐œ™(๐‘‡๐‘ฅ,๐‘‡๐‘ฆ)โ‰ค๐œ™(๐‘ฅ,๐‘ฆ) for ๐‘ฅ,๐‘ฆโˆˆ๐ถ. ๐‘‡ is said to be quas-ฯ•-nonexpansive if ๐น(๐‘‡)โ‰ โˆ… and ๐œ™(๐‘,๐‘‡๐‘ฅ)โ‰ค๐œ™(๐‘,๐‘ฅ) for ๐‘ฅโˆˆ๐ถ and ๐‘โˆˆ๐น(๐‘‡). A mapping ๐‘‡ is said to be asymptotically relatively nonexpansive, if ๐น(๐‘‡)โ‰ โˆ…, and there exists a real sequence {๐‘˜๐‘›}โŠ‚[1,โˆž) with ๐‘˜๐‘›โ†’1 such that ๐œ™(๐‘,๐‘‡๐‘›๐‘ฅ)โ‰ค๐‘˜๐‘›๐œ™(๐‘,๐‘ฅ), forall๐‘›โ‰ฅ1,๐‘ฅโˆˆ๐ถ, and ๐‘โˆˆ๐น(๐‘‡). {๐‘‡๐‘›}โˆž๐‘›=0 is said to be a countable family of weak relatively nonexpansive mappings [23] if the following conditions are satisfied: (i)๐น({๐‘‡๐‘›}โˆž๐‘›=0)โ‰ โˆ…; (ii)๐œ™(๐‘ข,๐‘‡๐‘›๐‘ฅ)โ‰ค๐œ™(๐‘ข,๐‘ฅ),forall๐‘ขโˆˆ๐น(๐‘‡๐‘›),๐‘ฅโˆˆ๐ถ,๐‘›โ‰ฅ0; (iii)๎๐น({๐‘‡๐‘›}โˆž๐‘›=0)=โˆฉโˆž๐‘›=0๐น(๐‘‡๐‘›). A mapping ๐‘‡โˆถ๐ถโ†’๐ถ is said to be uniformly L-Lipschitz continuous, if there exists a constant ๐ฟ>0 such that โ€–๐‘‡๐‘›๐‘ฅโˆ’๐‘‡๐‘›๐‘ฆโ€–โ‰ค๐ฟโ€–๐‘ฅโˆ’๐‘ฆโ€–,โˆ€๐‘ฅ,๐‘ฆโˆˆ๐ถ,โˆ€๐‘›โ‰ฅ1.(1.10) A mapping ๐‘‡โˆถ๐ถโ†’๐ถ is said to be closed if for any sequence {๐‘ฅ๐‘›}โŠ‚๐ถ with ๐‘ฅ๐‘›โ†’๐‘ฅ and ๐‘‡๐‘ฅ๐‘›โ†’๐‘ฆ, then ๐‘‡๐‘ฅ=๐‘ฆ. Let {๐‘‡๐‘–}โˆž๐‘–=1โˆถ๐ถโ†’๐ถ be a sequence of mappings. {๐‘‡๐‘–}โˆž๐‘–=1 is said to be a countable family of uniformly asymptotically relatively nonexpansive mappings, if โˆฉโˆž๐‘›=1๐น(๐‘‡๐‘›)โ‰ โˆ…, and there exists a sequence {๐‘˜๐‘›}โŠ‚[1,โˆž) with ๐‘˜๐‘›โ†’1 such that for each ๐‘–>1๐œ™๎€ท๐‘,๐‘‡๐‘›๐‘–๐‘ฅ๎€ธโ‰ค๐‘˜๐‘›๐œ™(๐‘,๐‘ฅ),โˆ€๐‘โˆˆโˆž๎™๐‘›=1๐น๎€ท๐‘‡๐‘›๎€ธ,๐‘ฅโˆˆ๐ถ,โˆ€๐‘›โ‰ฅ1.(1.11)

In 2009, Petrot et al. [24], introduced a hybrid projection method for approximating a common element of the set of solutions of fixed points of hemirelatively nonexpansive (or quasi-๐œ™-nonexpansive) mappings in a uniformly convex and uniformly smooth Banach space:๐‘ฅ0โˆˆ๐ถ,๐ถ0๐‘ฆ=๐ถ,๐‘›=๐ฝโˆ’1๎€ท๐›ผ๐‘›๐ฝ๐‘ฅ๐‘›+๎€ท1โˆ’๐›ผ๐‘›๎€ธ๐ฝ๐‘‡๐‘›๐‘ง๐‘›๎€ธ,๐‘ง๐‘›=๐ฝโˆ’1๎€ท๐›ฝ๐‘›๐ฝ๐‘ฅ๐‘›+๎€ท1โˆ’๐›ฝ๐‘›๎€ธ๐ฝ๐‘‡๐‘›๐‘ฅ๐‘›๎€ธ,๐ถ๐‘›+1=๎€ฝ๐‘ฃโˆˆ๐ถ๐‘›๎€ทโˆถ๐œ™๐‘ฃ,๐‘ฆ๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘ฃ,๐‘ฅ๐‘›,๐‘ฅ๎€ธ๎€พ๐‘›+1=ฮ ๐ถ๐‘›+1๎€ท๐‘ฅ0๎€ธ.(1.12) They proved that the sequence {๐‘ฅ๐‘›} converges strongly to ๐‘โˆˆ๐น(๐‘‡), where ๐‘โˆˆฮ ๐น(๐‘‡)๐‘ฅ and ฮ ๐ถ is the generalized projection from ๐ธ onto ๐น(๐‘‡). Kumam and Wattanawitoon [25], introduced a hybrid iterative scheme for finding a common element of the set of common fixed points of two quasi-๐œ™-nonexpansive mappings and the set of solutions of an equilibrium problem in Banach spaces, by the following manner: ๐‘ฅ0โˆˆ๐ถ,๐ถ0๐‘ฆ=๐ถ๐‘›=๐ฝโˆ’1๎€ท๐›ผ๐‘›๐ฝ๐‘ฅ๐‘›+๎€ท1โˆ’๐›ผ๐‘›๎€ธ๐ฝ๐‘†๐‘ง๐‘›๎€ธ,๐‘ง๐‘›=๐ฝโˆ’1๎€ท๐›ฝ๐‘›๐ฝ๐‘ฅ๐‘›+๎€ท1โˆ’๐›ฝ๐‘›๎€ธ๐ฝ๐‘‡๐‘ฅ๐‘›๎€ธ,๐‘ข๐‘›๎€ท๐‘ขโˆˆ๐ถsuchthat๐‘“๐‘›๎€ธ+1,๐‘ฆ๐‘Ÿ๐‘›โŸจ๐‘ฆโˆ’๐‘ข๐‘›,๐ฝ๐‘ข๐‘›โˆ’๐ฝ๐‘ฆ๐‘›๐ถโŸฉโ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ,๐‘›+1=๎€ฝ๐‘งโˆˆ๐ถ๐‘›๎€ทโˆถ๐œ™๐‘ง,๐‘ข๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›,๐‘ฅ๎€ธ๎€พ๐‘›+1=ฮ ๐ถ๐‘›+1๎€ท๐‘ฅ0๎€ธ.(1.13) They proved that the sequence {๐‘ฅ๐‘›} converges strongly to ๐‘โˆˆ๐น(๐‘‡)โˆฉ๐น(๐‘†)โˆฉEP(๐‘“), where ๐‘โˆˆฮ ๐น(๐‘‡)โˆฉ๐น(๐‘†)โˆฉEP(๐‘“)๐‘ฅ under the assumptions (C1) limsup๐‘›โ†’โˆž๐›ผ๐‘›<1, (C2) lim๐‘›โ†’โˆž๐›ฝ๐‘›<1, and (C3) liminf๐‘›โ†’โˆž(1โˆ’๐›ผ๐‘›)๐›ฝ๐‘›(1โˆ’๐›ฝ๐‘›)>0.

Recently, Chang et al. [26], introduced the modified block iterative method to propose an algorithm for solving the convex feasibility problems for an infinite family of quasi-๐œ™-asymptotically nonexpansive mappings,๐‘ฅ0โˆˆ๐ถchosenarbitrary,๐ถ0๐‘ฆ=๐ถ,๐‘›=๐ฝโˆ’1๎ƒฉ๐›ผ๐‘›,0๐ฝ๐‘ฅ๐‘›+โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–๐ฝ๐‘†๐‘›๐‘–๐‘ฅ๐‘›๎ƒช,๐ถ๐‘›+1=๎€ฝ๐‘ฃโˆˆ๐ถ๐‘›๎€ทโˆถ๐œ™๐‘ฃ,๐‘ฆ๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘ฃ,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›๎€พ,๐‘ฅ๐‘›+1=ฮ ๐ถ๐‘›+1๐‘ฅ0,โˆ€๐‘›โ‰ฅ0,(1.14)where ๐œ‰๐‘›=sup๐‘ขโˆˆ๐น(๐‘˜๐‘›โˆ’1)๐œ™(๐‘ข,๐‘ฅ๐‘›). Then, they proved that under appropriate control conditions the sequence {๐‘ฅ๐‘›} converges strongly to ฮ โˆฉโˆž๐‘›=1๐น(๐‘†๐‘–)๐‘ฅ0.

Very recently, Tan and Chang [27], introduced a new hybrid iterative scheme for finding a common element between set of solutions for a system of generalized mixed equilibrium problems, set of common fixed points of a family of quasi-๐œ™-asymptotically nonexpansive mappings (which is more general than quasi-๐œ™-nonexpansive mappings), and null spaces of finite family of ๐›พ-inverse strongly monotone mappings in a 2-uniformly convex and uniformly smooth real Banach space.

In this paper, motivated and inspired by Petrot et al. [24], Kumam and Wattanawitoon [25], Chang et al. [26], and Tan and Chang [27], we introduce the new hybrid block algorithm for two countable families of closed and uniformly Lipschitz continuous and uniformly asymptotically relatively nonexpansive mappings in a Banach space. Let {๐‘ฅ๐‘›} be a sequence defined by ๐‘ฅ0โˆˆ๐ถ, ๐ถ0=๐ถ and ๐‘ฆ๐‘›=๐ฝโˆ’1๎ƒฉ๐›ฝ๐‘›,0๐ฝ๎€ท๐‘ฅ๐‘›๎€ธ+โˆž๎“๐‘–=1๐›ฝ๐‘›,๐‘–๐ฝ๎€ท๐‘‡๐‘›๐‘–๐‘ฅ๐‘›๎€ธ๎ƒช,๐‘ง๐‘›=๐ฝโˆ’1๎ƒฉ๐›ผ๐‘›,0๐ฝ๎€ท๐‘ฅ๐‘›๎€ธ+โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–๐ฝ๎€ท๐‘†๐‘›๐‘–๐‘ฆ๐‘›๎€ธ๎ƒช,๐‘ข๐‘›(๐‘–)=๐พ๐‘“๐‘–,๐‘Ÿ๐‘–๐พ๐‘“๐‘–โˆ’1,๐‘Ÿ๐‘–โˆ’1โ‹ฏ๐พ๐‘“1,๐‘Ÿ1๎€ท๐‘ง๐‘›๎€ธ๐ถ,๐‘–=1,2,โ€ฆ,๐‘,๐‘›+1=๎ƒฏ๐‘งโˆˆ๐ถ๐‘›โˆถmax๐‘–=1,2,โ€ฆ,๐‘๐œ™๎‚€๐‘ง,๐‘ข๐‘›(๐‘–)๎‚๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ+๐œƒ๐‘›๎€ท,๐œ™๐‘ง,๐‘ฆ๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›๎ƒฐ,๐‘ฅ๐‘›+1=ฮ ๐ถ๐‘›+1๐‘ฅ0,โˆ€๐‘›โ‰ฅ0.(1.15) Under appropriate conditions, we will prove that the sequence {๐‘ฅ๐‘›} generated by algorithms (1.15) converges strongly to the point ฮ (โˆฉ๐‘๐‘–=1ฮฉ๐‘–)โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘‡๐‘–))โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘†๐‘–))๐‘ฅ0. Our results extend many known recent results in the literature.

2. Preliminaries

Let ๐ธ be a real Banach space with norm โ€–โ‹…โ€–, and let ๐ฝ be the normalized duality mapping from ๐ธ into 2๐ธโˆ— given by ๎€ฝ๐‘ฅ๐ฝ๐‘ฅ=โˆ—โˆˆ๐ธโˆ—โˆถโŸจ๐‘ฅ,๐‘ฅโˆ—โŸฉ=โ€–๐‘ฅโ€–โ€–๐‘ฅโˆ—โ€–,โ€–๐‘ฅโ€–=โ€–๐‘ฅโˆ—โ€–๎€พ(2.1) for all ๐‘ฅโˆˆ๐ธ, where ๐ธโˆ— denotes the dual space of ๐ธ and โŸจโ‹…,โ‹…โŸฉ the generalized duality pairing between ๐ธ and ๐ธโˆ—. It is also known that if ๐ธ is uniformly smooth, then ๐ฝ is uniformly norm-to-norm continuous on each bounded subset of ๐ธ.

We know the following (see [28, 29]):(i)if ๐ธ is smooth, then ๐ฝ is single valued;(ii)if ๐ธ is strictly convex, then ๐ฝ is one-to-one and โŸจ๐‘ฅโˆ’๐‘ฆ,๐‘ฅโˆ—โˆ’๐‘ฆโˆ—โŸฉ>0 holds for all (๐‘ฅ,๐‘ฅโˆ—),(๐‘ฆ,๐‘ฆโˆ—)โˆˆ๐ฝ with ๐‘ฅโ‰ ๐‘ฆ;(iii)if ๐ธ is reflexive, then ๐ฝ is surjective;(iv)if ๐ธ is uniformly convex, then it is reflexive;(v)if ๐ธ is a reflexive and strictly convex, then ๐ฝโˆ’1 is norm-weak-continuous;(vi)๐ธ is uniformly smooth if and only if ๐ธโˆ— is uniformly convex;(vii)if ๐ธโˆ— is uniformly convex, then ๐ฝ is uniformly norm-to-norm continuous on each bounded subset of ๐ธ;(viii)each uniformly convex Banach space ๐ธ has the Kadec-Klee property, that is, for any sequence {๐‘ฅ๐‘›}โŠ‚๐ธ, if ๐‘ฅ๐‘›โ‡€๐‘ฅโˆˆ๐ธ and โ€–๐‘ฅ๐‘›โ€–โ†’โ€–๐‘ฅโ€–, then ๐‘ฅ๐‘›โ†’๐‘ฅ.

Let ๐ธ be a smooth, strictly convex, and reflexive Banach space, and let ๐ถ be a nonempty closed convex subset of ๐ธ. Throughout this paper, we denote by ๐œ™ the function defined by ๐œ™(๐‘ฅ,๐‘ฆ)=โ€–๐‘ฅโ€–2โˆ’2โŸจ๐‘ฅ,๐ฝ๐‘ฆโŸฉ+โ€–๐‘ฆโ€–2,for๐‘ฅ,๐‘ฆโˆˆ๐ธ.(2.2) Following Alber [30], the generalized projection ฮ ๐ถโˆถ๐ธโ†’๐ถ is a map that assigns to an arbitrary point ๐‘ฅโˆˆ๐ธ the minimum point of the function ๐œ™(๐‘ฅ,๐‘ฆ), that is, ฮ ๐ถ๐‘ฅ=๐‘ฅ, where ๐‘ฅ is the solution to the minimization problem ๐œ™๎€ท๎€ธ๐‘ฅ,๐‘ฅ=inf๐‘ฆโˆˆ๐ถ๐œ™(๐‘ฆ,๐‘ฅ).(2.3) Existence and uniqueness of the operator ฮ ๐ถ follows from the properties of the functional ๐œ™(๐‘ฅ,๐‘ฆ) and strict monotonicity of the mapping ๐ฝ. It is obvious from the definition of function ๐œ™ that (see [30]) (โ€–๐‘ฆโ€–โˆ’โ€–๐‘ฅโ€–)2)โ‰ค๐œ™(๐‘ฆ,๐‘ฅ)โ‰ค(โ€–๐‘ฆโ€–+โ€–๐‘ฅโ€–2,โˆ€๐‘ฅ,๐‘ฆโˆˆ๐ธ.(2.4) If ๐ธ is a Hilbert space, then ๐œ™(๐‘ฅ,๐‘ฆ)=โ€–๐‘ฅโˆ’๐‘ฆโ€–2.

If ๐ธ is a reflexive, strictly convex, and smooth Banach space, then for ๐‘ฅ,๐‘ฆโˆˆ๐ธ, ๐œ™(๐‘ฅ,๐‘ฆ)=0 if and only if ๐‘ฅ=๐‘ฆ. It is sufficient to show that if ๐œ™(๐‘ฅ,๐‘ฆ)=0, then ๐‘ฅ=๐‘ฆ. From (2.4), we have โ€–๐‘ฅโ€–=โ€–๐‘ฆโ€–. This implies that โŸจ๐‘ฅ,๐ฝ๐‘ฆโŸฉ=โ€–๐‘ฅโ€–2=โ€–๐ฝ๐‘ฆโ€–2. From the definition of ๐ฝ, one has ๐ฝ๐‘ฅ=๐ฝ๐‘ฆ. Therefore, we have ๐‘ฅ=๐‘ฆ; see [28, 29] for more details.

We also need the following lemmas for the proof of our main results.

Lemma 2.1 (see Kamimura and Takahashi [31]). Let ๐ธ be a uniformly convex and smooth real Banach space, and let {๐‘ฅ๐‘›},{๐‘ฆ๐‘›} be two sequences of ๐ธ. If ๐œ™(๐‘ฅ๐‘›,๐‘ฆ๐‘›)โ†’0 and either {๐‘ฅ๐‘›} or {๐‘ฆ๐‘›} is bounded, then โ€–๐‘ฅ๐‘›โˆ’๐‘ฆ๐‘›โ€–โ†’0.

Lemma 2.2 (see Alber [30]). Let ๐ถ be a nonempty closed convex subset of a smooth Banach space ๐ธ and ๐‘ฅโˆˆ๐ธ. Then, ๐‘ฅ0=ฮ ๐ถ๐‘ฅ if and only if โŸจ๐‘ฅ0โˆ’๐‘ฆ,๐ฝ๐‘ฅโˆ’๐ฝ๐‘ฅ0โŸฉโ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ.(2.5)

Lemma 2.3 (see Alber [30]). Let ๐ธ be a reflexive, strictly convex, and smooth Banach space, let ๐ถ be a nonempty closed convex subset of ๐ธ, and let ๐‘ฅโˆˆ๐ธ. Then ๐œ™๎€ท๐‘ฆ,ฮ ๐ถ๐‘ฅ๎€ธ๎€ทฮ +๐œ™๐ถ๎€ธ๐‘ฅ,๐‘ฅโ‰ค๐œ™(๐‘ฆ,๐‘ฅ),โˆ€๐‘ฆโˆˆ๐ถ.(2.6)

Lemma 2.4 (see Chang et al. [26]). Let ๐ธ be a uniformly convex Banach space, ๐‘Ÿ>0 a positive number, and ๐ต๐‘Ÿ(0) a closed ball of ๐ธ. Then, for any given sequence {๐‘ฅ๐‘–}โˆž๐‘–=1โŠ‚๐ต๐‘Ÿ(0) and for any given sequence {๐œ†๐‘–}โˆž๐‘–=1 of positive number with โˆ‘โˆž๐‘›=1๐œ†๐‘›=1, there exists a continuous, strictly increasing, and convex function ๐‘”โˆถ[0,2๐‘Ÿ)โ†’[0,โˆž) with ๐‘”(0)=0 such that for any positive integers ๐‘–,๐‘— with ๐‘–<๐‘—, โ€–โ€–โ€–โ€–โˆž๎“๐‘›=1๐œ†๐‘›๐‘ฅ๐‘›โ€–โ€–โ€–โ€–2โ‰คโˆž๎“๐‘›=1๐œ†๐‘›โ€–โ€–๐‘ฅ๐‘›โ€–โ€–2โˆ’๐œ†๐‘–๐œ†๐‘—๐‘”๎€ทโ€–โ€–๐‘ฅ๐‘–โˆ’๐‘ฅ๐‘—โ€–โ€–๎€ธ.(2.7)

Lemma 2.5 (see Chang et al. [26]). Let ๐ธ be a real uniformly smooth and strictly convex Banach space with Kadec-Klee property, and ๐ถ be a nonempty closed convex subset of ๐ธ. Let ๐‘‡โˆถ๐ถโ†’๐ถ be a closed and asymptotically relatively nonexpansive mapping with a sequence {๐‘˜๐‘›}โŠ‚[1,โˆž),๐‘˜๐‘›โ†’1. Then ๐น(๐‘‡) is closed and convex subset of ๐ถ.

For solving the generalized mixed equilibrium problem (or a system of generalized mixed equilibrium problem), let us assume that the bifunction ๐‘“โˆถ๐ถร—๐ถโ†’โ„ and ๐œ“โˆถ๐ถโ†’โ„ is convex and lower semicontinuous satisfies the following conditions: (A1)๐‘“(๐‘ฅ,๐‘ฅ)=0 for all ๐‘ฅโˆˆ๐ถ; (A2)๐‘“ is monotone, that is, ๐‘“(๐‘ฅ,๐‘ฆ)+๐‘“(๐‘ฆ,๐‘ฅ)โ‰ค0 for all ๐‘ฅ,๐‘ฆโˆˆ๐ถ; (A3) for each ๐‘ฅ,๐‘ฆ,๐‘งโˆˆ๐ถ, limsup๐‘กโ†“0๐‘“(๐‘ก๐‘ง+(1โˆ’๐‘ก)๐‘ฅ,๐‘ฆ)โ‰ค๐‘“(๐‘ฅ,๐‘ฆ);(2.8)(A4) for each ๐‘ฅโˆˆ๐ถ, ๐‘ฆโ†ฆ๐‘“(๐‘ฅ,๐‘ฆ) is convex and lower semicontinuous.

Lemma 2.6 (see Chang et al. [26]). Let ๐ถ be a closed convex subset of a smooth, strictly convex, and reflexive Banach space ๐ธ. Let ๐ดโˆถ๐ถโ†’๐ธโˆ— be a continuous and monotone mapping, ๐œ“โˆถ๐ถโ†’โ„ is convex and lower semicontinuous and ๐‘“ be a bifunction from ๐ถร—๐ถ to โ„ satisfying (A1)โ€“(A4). For ๐‘Ÿ>0 and ๐‘ฅโˆˆ๐ธ, then there exists ๐‘ขโˆˆ๐ถ such that 1๐‘“(๐‘ข,๐‘ฆ)+โŸจ๐ด๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐œ“(๐‘ฆ)โˆ’๐œ“(๐‘ข)+๐‘ŸโŸจ๐‘ฆโˆ’๐‘ข,๐ฝ๐‘ขโˆ’๐ฝ๐‘ฅโŸฉโ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ.(2.9) Define a mapping ๐พ๐‘“,๐‘Ÿโˆถ๐ถโ†’๐ถ as follows: ๐พ๐‘“,๐‘Ÿ๎‚†1(๐‘ฅ)=๐‘ขโˆˆ๐ถโˆถ๐‘“(๐‘ข,๐‘ฆ)+โŸจ๐ด๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐œ“(๐‘ฆ)โˆ’๐œ“(๐‘ข)+๐‘Ÿ๎‚‡โŸจ๐‘ฆโˆ’๐‘ข,๐ฝ๐‘ขโˆ’๐ฝ๐‘ฅโŸฉโ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ(2.10) for all ๐‘ฅโˆˆ๐ธ. Then, the following hold: (i)๐พ๐‘“,๐‘Ÿ is singlevalued; (ii)๐พ๐‘“,๐‘Ÿ is firmly nonexpansive, that is, for all ๐‘ฅ,๐‘ฆโˆˆ๐ธ, โŸจ๐พ๐‘“,๐‘Ÿ๐‘ฅโˆ’๐พ๐‘“,๐‘Ÿ๐‘ฆ,๐ฝ๐พ๐‘“,๐‘Ÿ๐‘ฅโˆ’๐ฝ๐พ๐‘“,๐‘Ÿ๐‘ฆโŸฉโ‰คโŸจ๐พ๐‘“,๐‘Ÿ๐‘ฅโˆ’๐พ๐‘“,๐‘Ÿ๐‘ฆ,๐ฝ๐‘ฅโˆ’๐ฝ๐‘ฆโŸฉ;(iii)๐น(๐พ๐‘“,๐‘Ÿ๎„Ÿ)=๐น(๐พ๐‘“,๐‘Ÿ); (iv)๐‘ขโˆˆ๐ถ is a solution of variational equation (2.9) if and only if ๐‘ขโˆˆ๐ถ is a fixed point of ๐พ๐‘“,๐‘Ÿ; (v)๐น(๐พ๐‘“,๐‘Ÿ)=ฮฉ; (vi)ฮฉ is closed and convex; (vii)๐œ™(๐‘,๐พ๐‘“,๐‘Ÿ๐‘ง)+๐œ™(๐พ๐‘“,๐‘Ÿ๐‘ง,๐‘ง)โ‰ค๐œ™(๐‘,๐‘ง), forall๐‘โˆˆ๐น(๐พ๐‘“,๐‘Ÿ), ๐‘งโˆˆ๐ธ.

3. Main Results

Theorem 3.1. Let ๐ธ be a uniformly smooth and uniformly convex Banach space, let ๐ถ be a nonempty, closed, and convex subset of ๐ธ. Let ๐ด๐‘–โˆถ๐ถโ†’๐ธโˆ— be a continuous and monotone mapping, ๐œ“๐‘–โˆถ๐ถโ†’โ„ be a lower semi-continuous and convex function, ๐‘“๐‘– be a bifunction from ๐ถร—๐ถ to โ„ satisfying (A1)โ€“(A4), ๐พ๐‘“๐‘–,๐‘Ÿ๐‘– is the mapping defined by (2.10) where ๐‘Ÿ๐‘–โ‰ฅ๐‘Ÿ>0, and let {๐‘‡๐‘–}โˆž๐‘–=1, {๐‘†๐‘–}โˆž๐‘–=1 be countable families of closed and uniformly ๐ฟ๐‘–, ๐œ‡๐‘–-Lipschitz continuous and asymptotically relatively nonexpansive mapping with sequence {๐‘˜๐‘›},{๐œ๐‘›}โŠ‚[1,โˆž);โ€‰โ€‰๐‘˜๐‘›โ†’1,๐œ๐‘›โ†’1 such that โ„ฑโˆถ=(โˆฉ๐‘๐‘–=1ฮฉ๐‘–)โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘‡๐‘–))โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘†๐‘–))โ‰ โˆ…. Let {๐‘ฅ๐‘›} be a sequence generated by ๐‘ฅ0โˆˆ๐ถ and ๐ถ0=๐ถ, ๐‘ฆ๐‘›=๐ฝโˆ’1๎ƒฉ๐›ฝ๐‘›,0๐ฝ๎€ท๐‘ฅ๐‘›๎€ธ+โˆž๎“๐‘–=1๐›ฝ๐‘›,๐‘–๐ฝ๎€ท๐‘‡๐‘›๐‘–๐‘ฅ๐‘›๎€ธ๎ƒช,๐‘ง๐‘›=๐ฝโˆ’1๎ƒฉ๐›ผ๐‘›,0๐ฝ๎€ท๐‘ฅ๐‘›๎€ธ+โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–๐ฝ๎€ท๐‘†๐‘›๐‘–๐‘ฆ๐‘›๎€ธ๎ƒช,๐‘ข๐‘›(๐‘–)=๐พ๐‘“๐‘–,๐‘Ÿ๐‘–๐พ๐‘“๐‘–โˆ’1,๐‘Ÿ๐‘–โˆ’1โ‹ฏ๐พ๐‘“1,๐‘Ÿ1๎€ท๐‘ง๐‘›๎€ธ๐ถ,๐‘–=1,2,โ€ฆ,๐‘,๐‘›+1=๎‚ป๐‘งโˆˆ๐ถ๐‘›โˆถmax๐‘–=1,2,โ€ฆ,๐‘๐œ™๎‚€๐‘ง,๐‘ข๐‘›(๐‘–)๎‚๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ+๐œƒ๐‘›๎€ท,๐œ™๐‘ง,๐‘ฆ๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›๎‚ผ,๐‘ฅ๐‘›+1=ฮ ๐ถ๐‘›+1๐‘ฅ0,โˆ€๐‘›โ‰ฅ0,(3.1) where ๐œ‰๐‘›=sup๐‘โˆˆโ„ฑ(๐‘˜๐‘›โˆ’1)๐œ™(๐‘,๐‘ฅ๐‘›), ๐œƒ๐‘›=๐›ฟ๐‘›+๐œ‰๐‘›๐œ๐‘›, and ๐›ฟ๐‘›=sup๐‘โˆˆโ„ฑ(๐œ๐‘›โˆ’1)๐œ™(๐‘,๐‘ฅ๐‘›). The coefficient sequences {๐›ผ๐‘›,๐‘–} and {๐›ฝ๐‘›,๐‘–}โŠ‚[0,1] satisfy the following: (i)โˆ‘โˆž๐‘–=0๐›ผ๐‘›,๐‘–=1; (ii)โˆ‘โˆž๐‘–=0๐›ฝ๐‘›,๐‘–=1; (iii)liminf๐‘›โ†’โˆž๐›ผ๐‘›,0๐›ผ๐‘›,๐‘–>0, forall๐‘–โ‰ฅ1; (iv)liminf๐‘›โ†’โˆž๐›ฝ๐‘›,0๐›ฝ๐‘›,๐‘–>0, forall๐‘–โ‰ฅ1, ฮฉ๐‘–,๐‘–=1,2,โ€ฆ,๐‘ is the set of solutions to the following generalized mixed equilibrium problem: ๐‘“๐‘–(๐‘ง,๐‘ฆ)+โŸจ๐ด๐‘–๐‘ง,๐‘ฆโˆ’๐‘งโŸฉ+๐œ“๐‘–(๐‘ฆ)โˆ’๐œ“๐‘–(๐‘ง)โ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ,๐‘–=1,2,โ€ฆ,๐‘.(3.2) Then the sequence {๐‘ฅ๐‘›} converges strongly to ฮ โ„ฑ๐‘ฅ0.

Proof. We first show that ๐ถ๐‘›, forall๐‘›โ‰ฅ0 is closed and convex. Clearly ๐ถ0=๐ถ is closed and convex. Suppose that ๐ถ๐‘˜ is closed and convex for some ๐‘˜>1. For each ๐‘งโˆˆ๐ถ๐‘˜, we see that ๐œ™(๐‘ง,๐‘ข๐‘˜(๐‘–))โ‰ค๐œ™(๐‘ง,๐‘ฅ๐‘˜) is equivalent to 2๎‚€โŸจ๐‘ง,๐‘ฅ๐‘˜๎‚ฌโŸฉโˆ’๐‘ง,๐‘ข๐‘˜(๐‘–)โ‰คโ€–โ€–๐‘ฅ๎‚ญ๎‚๐‘˜โ€–โ€–2โˆ’โ€–โ€–๐‘ข๐‘˜(๐‘–)โ€–โ€–2.(3.3) By the set of ๐ถ๐‘˜+1, we have ๐ถ๐‘›+1=๎‚ป๐‘งโˆˆ๐ถ๐‘›โˆถmax๐‘–=1,2,โ€ฆ,๐‘๐œ™๎‚€๐‘ง,๐‘ข๐‘›(๐‘–)๎‚๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ+๐œƒ๐‘›๎‚ผ=๐‘๎™๐‘–=1๎‚†๎‚€๐‘งโˆˆ๐ถโˆถ๐œ™๐‘ง,๐‘ข๐‘›(๐‘–)๎‚๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ+๐œƒ๐‘›๎‚‡.(3.4) Hence, ๐ถ๐‘›+1 is also closed and convex.
By taking ฮ˜๐‘—๐‘›=๐พ๐‘Ÿ๐‘—,๐‘“๐‘–๐พ๐‘Ÿ๐‘—โˆ’1,๐‘“๐‘—โˆ’1โ‹ฏ๐พ๐‘Ÿ1,๐‘“1 for any ๐‘—โˆˆ{1,2,โ€ฆ,๐‘–} and ฮ˜0๐‘›=๐ผ for all ๐‘›โ‰ฅ1. We note that ๐‘ข๐‘›(๐‘–)=ฮ˜๐‘–๐‘›๐‘ง๐‘›.
Next, we show that โ„ฑโŠ‚๐ถ๐‘›,forall๐‘›โ‰ฅ1. For ๐‘›โ‰ฅ1, we have โ„ฑโŠ‚๐ถ=๐ถ1. For any given ๐‘โˆˆโ„ฑโˆถ=(โˆฉ๐‘๐‘–=1ฮฉ๐‘–)โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘‡๐‘–))โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘†๐‘–)). By (3.1) and Lemma 2.4, we have ๐œ™๎€ท๐‘,๐‘ฆ๐‘›๎€ธ๎ƒฉ=๐œ™๐‘,๐ฝโˆ’1๎ƒฉโˆž๎“๐‘–=0๐›ฝ๐‘›,๐‘–๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›๎ƒช๎ƒช=โ€–๐‘โ€–2โˆ’โˆž๎“๐‘–=0๐›ฝ๐‘›,๐‘–2๎ซ๐‘,๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›๎ฌ+โ€–โ€–โ€–โ€–โˆž๎“๐‘–=0๐›ฝ๐‘›,๐‘–๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–โ€–โ€–2โ‰คโ€–๐‘โ€–2โˆ’โˆž๎“๐‘–=0๐›ฝ๐‘›,๐‘–2๎ซ๐‘,๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›๎ฌ+โˆž๎“๐‘–=0๐›ฝ๐‘›,๐‘–โ€–โ€–๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–2โˆ’๐›ฝ๐‘›,0๐›ฝ๐‘›,๐‘–๐‘”๎€ทโ€–โ€–๐ฝ๐‘‡๐‘›0๐‘ฅ๐‘›โˆ’๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–๎€ธ=โ€–๐‘โ€–2โˆ’โˆž๎“๐‘–=0๐›ฝ๐‘›,๐‘–2๎ซ๐‘,๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›๎ฌ+โˆž๎“๐‘–=0๐›ฝ๐‘›,๐‘–โ€–โ€–๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–2โˆ’๐›ฝ๐‘›,0๐›ฝ๐‘›,๐‘–๐‘”๎€ทโ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–๎€ธ=โˆž๎“๐‘–=0๐›ฝ๐‘›,๐‘–๐œ™๎€ท๐‘,๐‘‡๐‘›๐‘–๐‘ฅ๐‘›๎€ธโˆ’๐›ฝ๐‘›,0๐›ฝ๐‘›,๐‘–๐‘”๎€ทโ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–๎€ธโ‰ค๐‘˜๐‘›๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธโˆ’๐›ฝ๐‘›,0๐›ฝ๐‘›,๐‘–๐‘”๎€ทโ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–๎€ธ๎€ทโ‰ค๐œ™๐‘,๐‘ฅ๐‘›๎€ธ+sup๐‘โˆˆ๐น๎€ท๐‘˜๐‘›๎€ธ๐œ™๎€ทโˆ’1๐‘,๐‘ฅ๐‘›๎€ธโˆ’๐›ฝ๐‘›,0๐›ฝ๐‘›,๐‘–๐‘”๎€ทโ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–๎€ธ๎€ทโ‰ค๐œ™๐‘,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›โˆ’๐›ฝ๐‘›,0๐›ฝ๐‘›,๐‘–๐‘”๎€ทโ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–๎€ธ๎€ทโ‰ค๐œ™๐‘,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›,(3.5) where ๐œ‰๐‘›=sup๐‘โˆˆโ„ฑ(๐‘˜๐‘›โˆ’1)๐œ™(๐‘,๐‘ฅ๐‘›).
By (3.1) and (3.5), we note that ๐œ™๎‚€๐‘,๐‘ข๐‘›(๐‘–)๎‚๎€ท=๐œ™๐‘,ฮ˜๐‘–๐‘›๐‘ง๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘,๐‘ง๐‘›๎€ธ๎ƒฉโ‰ค๐œ™๐‘,๐ฝโˆ’1๎ƒฉ๐›ผ๐‘›,0๐ฝ๐‘ฅ๐‘›+โˆž๎“๐‘–=1๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›๎ƒช๎ƒช=โ€–๐‘โ€–2๎„”โˆ’2๐‘,๐›ผ๐‘›,0๐ฝ๐‘ฅ๐‘›+โˆž๎“๐‘–=1๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›๎„•+โ€–โ€–โ€–โ€–๐›ผ๐‘›,0๐ฝ๐‘ฅ๐‘›+โˆž๎“๐‘–=1๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–โ€–โ€–2โ‰คโ€–๐‘โ€–2โˆ’2๐›ผ๐‘›,0โŸจ๐‘,๐ฝ๐‘ฅ๐‘›โŸฉโˆ’2โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–๎ซ๐‘,๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›๎ฌ+๐›ผ๐‘›,0โ€–โ€–๐‘ฅ๐‘›โ€–โ€–2+โˆž๎“๐‘–=1โ€–โ€–๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–2โˆ’๐›ผ๐‘›,0๐›ผ๐‘›,๐‘–๐‘”โ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–โ‰ค๐›ผ๐‘›,0๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธ+โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–๐œ™๎€ท๐‘,๐‘†๐‘›๐‘–๐‘ฆ๐‘›๎€ธโˆ’๐›ผ๐‘›,0๐›ผ๐‘›,๐‘–๐‘”โ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–โ‰ค๐›ผ๐‘›,0๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธ+๐œ๐‘›โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–๐œ™๎€ท๐‘,๐‘ฆ๐‘›๎€ธโˆ’๐›ผ๐‘›,0๐›ผ๐‘›,๐‘–๐‘”โ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–โ‰ค๐›ผ๐‘›,0๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธ+๐œ๐‘›โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–๎€ท๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›๎€ธโˆ’๐›ผ๐‘›,0๐›ผ๐‘›,๐‘–๐‘”โ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–โ‰ค๐›ผ๐‘›,0๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธ+๐œ๐‘›โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›๐œ๐‘›โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–โˆ’๐›ผ๐‘›,0๐›ผ๐‘›,๐‘–๐‘”โ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–โ‰ค๐œ๐‘›๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›๐œ๐‘›โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–โˆ’๐›ผ๐‘›,0๐›ผ๐‘›,๐‘–๐‘”โ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–๎€ทโ‰ค๐œ™๐‘,๐‘ฅ๐‘›๎€ธ+sup๐‘โˆˆ๐น๎€ท๐œ๐‘›๎€ธ๐œ™๎€ทโˆ’1๐‘,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›๐œ๐‘›โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–โˆ’๐›ผ๐‘›,0๐›ผ๐‘›,๐‘–๐‘”โ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–๎€ทโ‰ค๐œ™๐‘,๐‘ฅ๐‘›๎€ธ+๐›ฟ๐‘›+๐œ‰๐‘›๐œ๐‘›โˆ’๐›ผ๐‘›,0๐›ผ๐‘›,๐‘–๐‘”โ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–๎€ทโ‰ค๐œ™๐‘,๐‘ฅ๐‘›๎€ธ+๐œƒ๐‘›,(3.6) where ๐›ฟ๐‘›=sup๐‘โˆˆโ„ฑ(๐œ๐‘›โˆ’1)๐œ™(๐‘,๐‘ฅ๐‘›), ๐œƒ๐‘›=๐›ฟ๐‘›+๐œ‰๐‘›๐œ๐‘›. By assumptions on {๐‘˜๐‘›} and {๐œ๐‘›}, we have ๐œ‰๐‘›=sup๐‘โˆˆโ„ฑ๎€ท๐‘˜๐‘›๎€ธ๐œ™๎€ทโˆ’1๐‘,๐‘ฅ๐‘›๎€ธโ‰คsup๐‘โˆˆโ„ฑ๎€ท๐‘˜๐‘›๎€ธ()โˆ’1โ€–๐‘โ€–+๐‘€2๐›ฟโŸถ0as๐‘›โŸถโˆž,(3.7)๐‘›=sup๐‘โˆˆโ„ฑ๎€ท๐œ๐‘›๎€ธ๐œ™๎€ทโˆ’1๐‘,๐‘ฅ๐‘›๎€ธโ‰คsup๐‘โˆˆโ„ฑ๎€ท๐œ๐‘›๎€ธโˆ’1(โ€–๐‘โ€–+๐‘€)2โŸถ0as๐‘›โŸถโˆž,(3.8) where ๐‘€=sup๐‘›โ‰ฅ0โ€–๐‘ฅ๐‘›โ€–.
So, we have ๐‘โˆˆ๐ถ๐‘›+1. This implies that โ„ฑโˆˆ๐ถ๐‘›,forall๐‘›โ‰ฅ0 and also {๐‘ฅ๐‘›} is well defined.
From Lemma 2.2 and ๐‘ฅ๐‘›=ฮ ๐ถ๐‘›๐‘ฅ0, we have โŸจ๐‘ฅ๐‘›โˆ’๐‘ง,๐ฝ๐‘ฅ0โˆ’๐ฝ๐‘ฅ๐‘›โŸฉโ‰ฅ0,โˆ€๐‘งโˆˆ๐ถ๐‘›,โŸจ๐‘ฅ๐‘›โˆ’๐‘,๐ฝ๐‘ฅ0โˆ’๐ฝ๐‘ฅ๐‘›โŸฉโ‰ฅ0,โˆ€๐‘โˆˆ๐ถ๐‘›.(3.9) From Lemma 2.3, one has ๐œ™๎€ท๐‘ฅ๐‘›,๐‘ฅ0๎€ธ๎€ทฮ =๐œ™๐ถ๐‘›๐‘ฅ0,๐‘ฅ0๎€ธ๎€ทโ‰ค๐œ™๐‘,๐‘ฅ0๎€ธ๎€ทโˆ’๐œ™๐‘,๐‘ฅ๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘,๐‘ฅ0๎€ธ(3.10) for all ๐‘โˆˆโ„ฑโŠ‚๐ถ๐‘› and ๐‘›โ‰ฅ1. Then, the sequence {๐œ™(๐‘ฅ๐‘›,๐‘ฅ0)} is also bounded. Thus {๐‘ฅ๐‘›} is bounded. Since ๐‘ฅ๐‘›=ฮ ๐ถ๐‘›๐‘ฅ0 and ๐‘ฅ๐‘›+1=ฮ ๐ถ๐‘›+1๐‘ฅ0โˆˆ๐ถ๐‘›+1โŠ‚๐ถ๐‘›, we have ๐œ™๎€ท๐‘ฅ๐‘›,๐‘ฅ0๎€ธ๎€ท๐‘ฅโ‰ค๐œ™๐‘›+1,๐‘ฅ0๎€ธ,โˆ€๐‘›โˆˆโ„•.(3.11) Therefore, {๐œ™(๐‘ฅ๐‘›,๐‘ฅ0)} is nondecreasing. Hence, the limit of {๐œ™(๐‘ฅ๐‘›,๐‘ฅ0)} exists. By the construction of ๐ถ๐‘›, one has that ๐ถ๐‘šโŠ‚๐ถ๐‘› and ๐‘ฅ๐‘š=ฮ ๐ถ๐‘š๐‘ฅ0โˆˆ๐ถ๐‘› for any positive integer ๐‘šโ‰ฅ๐‘›. It follows that ๐œ™๎€ท๐‘ฅ๐‘š,๐‘ฅ๐‘›๎€ธ๎€ท๐‘ฅ=๐œ™๐‘š,ฮ ๐ถ๐‘›๐‘ฅ0๎€ธ๎€ท๐‘ฅโ‰ค๐œ™๐‘š,๐‘ฅ0๎€ธ๎€ทฮ โˆ’๐œ™๐ถ๐‘›๐‘ฅ0,๐‘ฅ0๎€ธ๎€ท๐‘ฅ=๐œ™๐‘š,๐‘ฅ0๎€ธ๎€ท๐‘ฅโˆ’๐œ™๐‘›,๐‘ฅ0๎€ธ.(3.12) Letting ๐‘š,๐‘›โ†’0 in (3.12), we get ๐œ™(๐‘ฅ๐‘š,๐‘ฅ๐‘›)โ†’0. It follows from Lemma 2.1, that โ€–๐‘ฅ๐‘šโˆ’๐‘ฅ๐‘›โ€–โ†’0 as ๐‘š,๐‘›โ†’โˆž. That is, {๐‘ฅ๐‘›} is a Cauchy sequence.
Since {๐‘ฅ๐‘›} is bounded and ๐ธ is reflexive, there exists a subsequence {๐‘ฅ๐‘›๐‘–}โŠ‚{๐‘ฅ๐‘›} such that ๐‘ฅ๐‘›๐‘–โ‡€๐‘ข. Since ๐ถ๐‘› is closed and convex and ๐ถ๐‘›+1โŠ‚๐ถ๐‘›, this implies that ๐ถ๐‘› is weakly closed and ๐‘ขโˆˆ๐ถ๐‘› for each ๐‘›โ‰ฅ0. since ๐‘ฅ๐‘›=ฮ ๐ถ๐‘›๐‘ฅ0, we have ๐œ™๎€ท๐‘ฅ๐‘›๐‘–,๐‘ฅ0๎€ธ๎€ทโ‰ค๐œ™๐‘ข,๐‘ฅ0๎€ธ,โˆ€๐‘›๐‘–โ‰ฅ0.(3.13) Since liminf๐‘›๐‘–โ†’โˆž๐œ™๎€ท๐‘ฅ๐‘›๐‘–,๐‘ฅ0๎€ธ=liminf๐‘›๐‘–โ†’โˆž๎‚†โ€–โ€–๐‘ฅ๐‘›๐‘–โ€–โ€–2๎ซ๐‘ฅโˆ’2๐‘›๐‘–,๐ฝ๐‘ฅ0๎ฌ+โ€–โ€–๐‘ฅ0โ€–โ€–2๎‚‡โ‰คโ€–๐‘ขโ€–2โˆ’2โŸจ๐‘ข,๐ฝ๐‘ฅ0โ€–โ€–๐‘ฅโŸฉ+0โ€–โ€–2๎€ท=๐œ™๐‘ข,๐‘ฅ0๎€ธ.(3.14) We have ๐œ™๎€ท๐‘ข,๐‘ฅ0๎€ธโ‰คliminf๐‘›๐‘–โ†’โˆž๐œ™๎€ท๐‘ฅ๐‘›๐‘–,๐‘ฅ0๎€ธโ‰คlimsup๐‘›๐‘–โ†’โˆž๐œ™๎€ท๐‘ฅ๐‘›๐‘–,๐‘ฅ0๎€ธ๎€ทโ‰ค๐œ™๐‘ข,๐‘ฅ0๎€ธ.(3.15) This implies that lim๐‘›๐‘–โ†’โˆž๐œ™(๐‘ฅ๐‘›๐‘–,๐‘ฅ0)=๐œ™(๐‘ข,๐‘ฅ0). That is, โ€–๐‘ฅ๐‘›๐‘–โ€–โ†’โ€–๐‘ขโ€–. Since ๐‘ฅ๐‘›๐‘–โ‡€๐‘ข, by the Kadec-klee property of ๐ธ, we obtain that lim๐‘›โ†’โˆž๐‘ฅ๐‘›๐‘–=๐‘ข.(3.16) If there exists some subsequence {๐‘ฅ๐‘›๐‘—}โŠ‚{๐‘ฅ๐‘›} such that ๐‘ฅ๐‘›๐‘—โ†’๐‘ž, then we have ๐œ™(๐‘ข,๐‘ž)=lim๐‘›๐‘–โ†’โˆž,๐‘›๐‘—โ†’โˆž๐œ™๎‚€๐‘ฅ๐‘›๐‘–,๐‘ฅ๐‘›๐‘—๎‚โ‰คlim๐‘›๐‘–โ†’โˆž,๐‘›๐‘—โ†’โˆž๎‚€๐œ™๎€ท๐‘ฅ๐‘›๐‘–,๐‘ฅ0๎€ธ๎‚€ฮ โˆ’๐œ™๐ถ๐‘›๐‘—๐‘ฅ0,๐‘ฅ0๎‚๎‚=lim๐‘›๐‘–โ†’โˆž,๐‘›๐‘—โ†’โˆž๎‚€๐œ™๎€ท๐‘ฅ๐‘›๐‘–,๐‘ฅ0๎€ธ๎‚€๐‘ฅโˆ’๐œ™๐‘›๐‘—๐‘ฅ0,๐‘ฅ0๎‚๎‚=0.(3.17) Therefore, we have ๐‘ข=๐‘ž. This implies that lim๐‘›โ†’โˆž๐‘ฅ๐‘›=๐‘ข.(3.18) Since ๐œ™๎€ท๐‘ฅ๐‘›+1,๐‘ฅ๐‘›๎€ธ๎€ท๐‘ฅ=๐œ™๐‘›+1,ฮ ๐ถ๐‘›๐‘ฅ0๎€ธ๎€ท๐‘ฅโ‰ค๐œ™๐‘›+1,๐‘ฅ0๎€ธ๎€ทฮ โˆ’๐œ™๐ถ๐‘›๐‘ฅ0,๐‘ฅ0๎€ธ๎€ท๐‘ฅ=๐œ™๐‘›+1,๐‘ฅ0๎€ธ๎€ท๐‘ฅโˆ’๐œ™๐‘›,๐‘ฅ0๎€ธ(3.19) for all ๐‘›โˆˆโ„•, we also have lim๐‘›โ†’โˆž๐œ™๎€ท๐‘ฅ๐‘›+1,๐‘ฅ๐‘›๎€ธ=0.(3.20) Since ๐‘ฅ๐‘›+1=ฮ ๐ถ๐‘›+1๐‘ฅ0โˆˆ๐ถ๐‘›+1 and by the definition of ๐ถ๐‘›+1, for ๐‘–=1,2,โ€ฆ,๐‘, we have ๐œ™๎€ท๐‘ฅ๐‘›+1,๐‘ข๐‘–๐‘›๎€ธ๎€ท๐‘ฅโ‰ค๐œ™๐‘›+1,๐‘ฅ๐‘›๎€ธ+๐œƒ๐‘›.(3.21) Noticing that lim๐‘›โ†’โˆž๐œ™(๐‘ฅ๐‘›+1,๐‘ฅ๐‘›)=0, we obtain lim๐‘›โ†’โˆž๐œ™๎€ท๐‘ฅ๐‘›+1,๐‘ข๐‘–๐‘›๎€ธ=0,for๐‘–=1,2,โ€ฆ,๐‘.(3.22) It then yields that lim๐‘›โ†’โˆž(โ€–๐‘ฅ๐‘›+1โ€–โˆ’โ€–๐‘ข๐‘–๐‘›โ€–)=0,forall๐‘–=1,2,โ€ฆ,๐‘. Since lim๐‘›โ†’โˆžโ€–๐‘ฅ๐‘›+1โ€–=โ€–๐‘ขโ€–, we have lim๐‘›โ†’โˆžโ€–โ€–๐‘ข๐‘–๐‘›โ€–โ€–=โ€–๐‘ขโ€–,โˆ€๐‘–=1,2,โ€ฆ,๐‘.(3.23) Hence, lim๐‘›โ†’โˆžโ€–โ€–๐ฝ๐‘ข๐‘–๐‘›โ€–โ€–=โ€–๐ฝ๐‘ขโ€–,โˆ€๐‘–=1,2,โ€ฆ,๐‘.(3.24) From Lemma 2.1 and (3.22), we have lim๐‘›โ†’โˆžโ€–โ€–๐‘ฅ๐‘›+1โˆ’๐‘ฅ๐‘›โ€–โ€–=lim๐‘›โ†’โˆžโ€–โ€–๐‘ฅ๐‘›+1โˆ’๐‘ข๐‘–๐‘›โ€–โ€–=0,โˆ€๐‘–=1,2,โ€ฆ,๐‘.(3.25) By the triangle inequality, we get lim๐‘›โ†’โˆžโ€–โ€–๐‘ฅ๐‘›โˆ’๐‘ข๐‘–๐‘›โ€–โ€–=0,โˆ€๐‘–=1,2,โ€ฆ,๐‘.(3.26) Since ๐ฝ is uniformly norm-to-norm continuous on bounded sets, we note that lim๐‘›โ†’โˆžโ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘ข๐‘–๐‘›โ€–โ€–=lim๐‘›โ†’โˆžโ€–โ€–๐ฝ๐‘ฅ๐‘›+1โˆ’๐ฝ๐‘ข๐‘–๐‘›โ€–โ€–=0,โˆ€๐‘–=1,2,โ€ฆ,๐‘.(3.27)
Now, we prove that ๐‘ขโˆˆ(โˆฉโˆž๐‘–=1๐น(๐‘‡๐‘–))โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘†๐‘–)). From the construction of ๐ถ๐‘›, we obtain that ๐œ™๎€ท๐‘ฅ๐‘›+1,๐‘ฆ๐‘›๎€ธ๎€ท๐‘ฅโ‰ค๐œ™๐‘›+1,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›.(3.28) From (3.7) and (3.20), we have lim๐‘›โ†’โˆž๐œ™๎€ท๐‘ฅ๐‘›+1,๐‘ฆ๐‘›๎€ธ=0.(3.29) By Lemma 2.1, we also have lim๐‘›โ†’โˆžโ€–โ€–๐‘ฅ๐‘›+1โˆ’๐‘ฆ๐‘›โ€–โ€–=0.(3.30) Since ๐ฝ is uniformly norm-to-norm continuous on bounded sets, we note that lim๐‘›โ†’โˆžโ€–โ€–๐ฝ๐‘ฅ๐‘›+1โˆ’๐ฝ๐‘ฆ๐‘›โ€–โ€–=0.(3.31) From (2.4) and (3.29), we have (โ€–๐‘ฅ๐‘›+1โ€–โˆ’โ€–๐‘ฆ๐‘›โ€–)2โ†’0. Since โ€–๐‘ฅ๐‘›+1โ€–โ†’โ€–๐‘ขโ€–, it yields that โ€–โ€–๐‘ฆ๐‘›โ€–โ€–โŸถโ€–๐‘ขโ€–as๐‘›โŸถโˆž.(3.32) Since ๐ฝ is uniformly norm-to-norm continuous on bounded sets, it follows that โ€–โ€–J๐‘ฆ๐‘›โ€–โ€–โŸถโ€–๐ฝ๐‘ขโ€–as๐‘›โŸถโˆž.(3.33) This implies that {๐ฝ๐‘ฆ๐‘›} is bounded in ๐ธโˆ—. Since ๐ธ is reflexive, there exists a subsequence {๐ฝ๐‘ฆ๐‘›๐‘–}โŠ‚{๐ฝ๐‘ฆ๐‘›} such that ๐ฝ๐‘ฆ๐‘›๐‘–โ‡€๐‘Ÿโˆˆ๐ธโˆ—. Since ๐ธ is reflexive, we see that ๐ฝ(๐ธ)=๐ธโˆ—. Hence, there exists ๐‘ฅโˆˆ๐ธ such that ๐ฝ๐‘ฅ=๐‘Ÿ. We note that ๐œ™๎€ท๐‘ฅ๐‘›๐‘–+1,๐‘ฆ๐‘›๐‘–๎€ธ=โ€–โ€–๐‘ฅ๐‘›๐‘–+1โ€–โ€–2๎ซ๐‘ฅโˆ’2๐‘›๐‘–+1,๐ฝ๐‘ฆ๐‘›๐‘–๎ฌ+โ€–โ€–๐‘ฆ๐‘›๐‘–โ€–โ€–2=โ€–โ€–๐‘ฅ๐‘›๐‘–+1โ€–โ€–2๎ซ๐‘ฅโˆ’2๐‘›๐‘–+1,๐ฝ๐‘ฆ๐‘›๐‘–๎ฌ+โ€–โ€–๐ฝ๐‘ฆ๐‘›๐‘–โ€–โ€–2.(3.34) Taking the limit interior of both side and in view of weak lower semicontinuity of norm โ€–โ‹…โ€–, we have 0โ‰ฅโ€–๐‘ขโ€–2โˆ’2โŸจ๐‘ข,๐‘ŸโŸฉ+โ€–๐‘Ÿโ€–2=โ€–๐‘ขโ€–2โˆ’2โŸจ๐‘ข,๐ฝ๐‘ฅโŸฉ+โ€–๐ฝ๐‘ฅโ€–2=โ€–๐‘ขโ€–2โˆ’2โŸจ๐‘ข,๐ฝ๐‘ฅโŸฉ+โ€–๐‘ฅโ€–2=๐œ™(๐‘ข,๐‘ฅ),(3.35) that is, ๐‘ข=๐‘ฅ. This implies that ๐‘Ÿ=๐ฝ๐‘ข and so ๐ฝ๐‘ฆ๐‘›โ‡€๐ฝ๐‘. It follows from lim๐‘›โ†’โˆžโ€–๐ฝ๐‘ฆ๐‘›โ€–=โ€–๐ฝ๐‘ขโ€–, as ๐‘›โ†’โˆž and the Kadec-Klee property of ๐ธโˆ— that ๐ฝ๐‘ฆ๐‘›๐‘–โ†’๐ฝ๐‘ข as ๐‘›โ†’โˆž. Note that ๐ฝโˆ’1โˆถ๐ธโˆ—โ†’๐ธ is hemicontinuous, it yields that ๐‘ฆ๐‘›๐‘–โ‡€๐‘ข. It follows from lim๐‘›โ†’โˆžโ€–๐‘ข๐‘›โ€–=โ€–๐‘ขโ€–, as ๐‘›โ†’โˆž and the Kadec-Klee property of ๐ธ that lim๐‘›๐‘–โ†’โˆž๐‘ฆ๐‘›๐‘–=๐‘ข.
By similar, we can prove that lim๐‘›โ†’โˆž๐‘ฆ๐‘›=๐‘ข.(3.36) By (3.20) and (3.30), we obtain lim๐‘›โ†’โˆžโ€–โ€–๐‘ฅ๐‘›โˆ’๐‘ฆ๐‘›โ€–โ€–=0.(3.37) Since ๐ฝ is uniformly norm-to-norm continuous on bounded sets, we note that lim๐‘›โ†’โˆžโ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘ฆ๐‘›โ€–โ€–=0.(3.38) So, from (3.27) and (3.31), by the triangle inequality, we get lim๐‘›โ†’โˆžโ€–โ€–๐ฝ๐‘ฆ๐‘›โˆ’๐ฝ๐‘ข๐‘–๐‘›โ€–โ€–=0,for๐‘–=1,2,โ€ฆ,๐‘.(3.39) Since ๐ฝโˆ’1 is uniformly norm-to-norm continuous on bounded sets, we note that lim๐‘›โ†’โˆžโ€–โ€–๐‘ฆ๐‘›โˆ’๐‘ข๐‘–๐‘›โ€–โ€–=0,for๐‘–=1,2,โ€ฆ,๐‘.(3.40) Since ๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธ๎€ทโˆ’๐œ™๐‘,๐‘ฆ๐‘›๎€ธ=โ€–โ€–๐‘ฅ๐‘›โ€–โ€–2โˆ’โ€–โ€–๐‘ฆ๐‘›โ€–โ€–2โˆ’2โŸจ๐‘,๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘ฆ๐‘›โŸฉโ‰คโ€–โ€–๐‘ฅ๐‘›โ€–โ€–2โˆ’โ€–โ€–๐‘ฆ๐‘›โ€–โ€–2โ€–โ€–+2โ€–๐‘โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘ฆ๐‘›โ€–โ€–โ‰คโ€–โ€–๐‘ฅ๐‘›โˆ’๐‘ฆ๐‘›โ€–โ€–๎€ทโ€–โ€–๐‘ฅ๐‘›โ€–โ€–+โ€–โ€–๐‘ฆ๐‘›โ€–โ€–๎€ธโ€–โ€–+2โ€–๐‘โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘ฆ๐‘›โ€–โ€–.(3.41) From (3.37) and (3.38), we obtain ๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธ๎€ทโˆ’๐œ™๐‘,๐‘ฆ๐‘›๎€ธโŸถ0,๐‘›โŸถโˆž.(3.42) On the other hand, we observe that, for ๐‘–=1,2,โ€ฆ,๐‘. ๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธ๎€ทโˆ’๐œ™๐‘,๐‘ข๐‘–๐‘›๎€ธ=โ€–โ€–๐‘ฅ๐‘›โ€–โ€–2โˆ’โ€–โ€–๐‘ข๐‘–๐‘›โ€–โ€–2๎ซโˆ’2๐‘,๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘ข๐‘–๐‘›๎ฌโ‰คโ€–โ€–๐‘ฅ๐‘›โ€–โ€–2โˆ’โ€–โ€–๐‘ข๐‘–๐‘›โ€–โ€–2โ€–โ€–+2โ€–๐‘โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘ข๐‘–๐‘›โ€–โ€–โ‰คโ€–โ€–๐‘ฅ๐‘›โˆ’๐‘ข๐‘–๐‘›โ€–โ€–๎€ทโ€–โ€–๐‘ฅ๐‘›โ€–โ€–+โ€–โ€–๐‘ข๐‘–๐‘›โ€–โ€–๎€ธโ€–โ€–+2โ€–๐‘โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘ข๐‘–๐‘›โ€–โ€–.(3.43) From (3.22) and (3.27), we have ๐œ™๎€ท๐‘,๐‘ฅ๐‘›๎€ธ๎€ทโˆ’๐œ™๐‘,๐‘ข๐‘–๐‘›๎€ธโŸถ0,๐‘›โŸถโˆž,โˆ€๐‘–=1,2,โ€ฆ,๐‘.(3.44) For any ๐‘โˆˆโˆฉ๐‘๐‘–=1ฮฉ๐‘–โˆฉ(โˆฉโˆž๐‘–=1F(๐‘‡๐‘–))โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘†๐‘–)), it follows from (3.5) that ๐›ฝ๐‘›,0๐›ฝ๐‘›,๐‘–๐‘”๎€ทโ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–๎€ธ๎€ทโ‰ค๐œ™๐‘,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›๎€ทโˆ’๐œ™๐‘,๐‘ฆ๐‘›๎€ธ.(3.45)From condition, liminf๐‘›โ†’โˆž๐›ฝ๐‘›,0๐›ฝ๐‘›,๐‘–>0, property of ๐‘”, (3.7), and (3.42), we have that โ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–โŸถ0,๐‘›โŸถโˆž,โˆ€๐‘–=1,2,โ€ฆ,๐‘.(3.46) Since ๐‘ฅ๐‘›โ†’๐‘ข and ๐ฝ is uniformly norm-to-norm continuous. It yields ๐ฝ๐‘ฅ๐‘›โ†’๐ฝ๐‘. Hence from (3.46), we have โ€–โ€–๐‘ฅ๐‘›โˆ’๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–โŸถ0,๐‘›โŸถโˆž,โˆ€๐‘–=1,2,โ€ฆ,๐‘.(3.47) Since ๐‘ฅ๐‘›โ†’๐‘ข, this implies that lim๐‘›โ†’โˆž๐ฝ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ†’๐ฝ๐‘ข as ๐‘›โ†’โˆž. Since ๐ฝโˆ’1โˆถ๐ธโˆ—โ†’๐ธ is hemicontinuous, it follows that ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ‡€๐‘ข,foreach๐‘–โ‰ฅ1.(3.48) On the other hand, for each ๐‘–โ‰ฅ1, we have โ€–โ€–๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–||โ€–โ€–๐‘‡โˆ’โ€–๐‘ขโ€–=๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–||โ‰คโ€–โ€–๐‘‡โˆ’โ€–๐‘ขโ€–๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–โˆ’๐‘ขโŸถ0,๐‘›โŸถโˆž.(3.49) from this, together with (3.48) and the Kadec-Klee property of ๐ธ, we obtain ๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โŸถ๐‘ข,foreach๐‘–โ‰ฅ1.(3.50) On the other hand, by the assumption that ๐‘‡๐‘– is uniformly ๐ฟ๐‘–-Lipschitz continuous, we have โ€–โ€–๐‘‡๐‘–๐‘›+1๐‘ฅ๐‘›โˆ’๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–โ‰คโ€–โ€–๐‘‡๐‘–๐‘›+1๐‘ฅ๐‘›โˆ’๐‘‡๐‘–๐‘›+1๐‘ฅ๐‘›+1โ€–โ€–+โ€–โ€–๐‘‡๐‘–๐‘›+1๐‘ฅ๐‘›+1โˆ’๐‘ฅ๐‘›+1โ€–โ€–+โ€–โ€–๐‘ฅ๐‘›+1โˆ’๐‘ฅ๐‘›โ€–โ€–+โ€–โ€–๐‘ฅ๐‘›โˆ’๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–โ‰ค๎€ท๐ฟ๐‘–๎€ธโ€–โ€–๐‘ฅ+1๐‘›+1โˆ’๐‘ฅ๐‘›โ€–โ€–+โ€–โ€–๐‘‡๐‘–๐‘›+1๐‘ฅ๐‘›+1โˆ’๐‘ฅ๐‘›+1โ€–โ€–+โ€–โ€–๐‘ฅ๐‘›โˆ’๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–.(3.51) By (3.18) and (3.50), we obtain lim๐‘›โ†’โˆžโ€–โ€–๐‘‡๐‘–๐‘›+1๐‘ฅ๐‘›โˆ’๐‘‡๐‘›๐‘–๐‘ฅ๐‘›โ€–โ€–=0,โˆ€๐‘–โ‰ฅ1,(3.52) and lim๐‘›โ†’โˆž๐‘‡๐‘–๐‘›+1๐‘ฅ๐‘›=๐‘ข, that is, ๐‘‡๐‘–๐‘‡๐‘›๐‘ฅ๐‘›โ†’๐‘ข, forall๐‘–โ‰ฅ1. By the closeness of ๐‘‡๐‘–, we have ๐‘‡๐‘–๐‘ข=u, forall๐‘–โ‰ฅ1. This implies that ๐‘ขโˆˆโˆฉโˆž๐‘–=1๐น(๐‘‡๐‘–).
By the similar way, we can prove that for each ๐‘–โ‰ฅ1โ€–โ€–๐ฝ๐‘ฅ๐‘›โˆ’๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–โŸถ0,๐‘›โŸถโˆž.(3.53) Since ๐‘ฅ๐‘›โ†’๐‘ข and ๐ฝ is uniformly norm-to-norm continuous. it yields ๐ฝ๐‘ฅ๐‘›โ†’๐ฝ๐‘. Hence from (3.53), we have โ€–โ€–๐‘ฅ๐‘›โˆ’๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–โŸถ0,๐‘›โŸถโˆž.(3.54) Since ๐‘ฅ๐‘›โ†’๐‘ข, this implies that lim๐‘›โ†’โˆž๐ฝ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ†’๐ฝ๐‘ข as ๐‘›โ†’โˆž. Since ๐ฝโˆ’1โˆถ๐ธโˆ—โ†’๐ธ is hemicontinuous, it follows that ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ‡€๐‘ข,foreach๐‘–โ‰ฅ1.(3.55) On the other hand, for each ๐‘–โ‰ฅ1, we have โ€–โ€–๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–||โ€–โ€–๐‘†โˆ’โ€–๐‘ขโ€–=๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–||โ‰คโ€–โ€–๐‘†โˆ’โ€–๐‘ขโ€–๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–โˆ’๐‘ขโŸถ0,๐‘›โŸถโˆž.(3.56) From this, together with (3.54) and the Kadec-Klee property of ๐ธ, we obtain ๐‘†๐‘›๐‘–๐‘ฆ๐‘›โŸถ๐‘ข,foreach๐‘–โ‰ฅ1.(3.57) On the other hand, by the assumption that ๐‘†๐‘– is uniformly ๐œ‡๐‘–-Lipschitz continuous, we have โ€–โ€–๐‘†๐‘–๐‘›+1๐‘ฆ๐‘›โˆ’๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–โ‰คโ€–โ€–๐‘†๐‘–๐‘›+1๐‘ฆ๐‘›โˆ’๐‘†๐‘–๐‘›+1๐‘ฆ๐‘›+1โ€–โ€–+โ€–โ€–๐‘†๐‘–๐‘›+1๐‘ฆ๐‘›+1โˆ’๐‘ฆ๐‘›+1โ€–โ€–+โ€–โ€–๐‘ฆ๐‘›+1โˆ’๐‘ฆ๐‘›โ€–โ€–+โ€–โ€–๐‘ฆ๐‘›โˆ’๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–โ‰ค๎€ท๐œ‡๐‘–๎€ธโ€–โ€–๐‘ฆ+1๐‘›+1โˆ’๐‘ฆ๐‘›โ€–โ€–+โ€–โ€–๐‘†๐‘–๐‘›+1๐‘ฆ๐‘›+1โˆ’๐‘ฆ๐‘›+1โ€–โ€–+โ€–โ€–๐‘ฆ๐‘›โˆ’๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–.(3.58) By (3.36) and (3.57), we obtain lim๐‘›โ†’โˆžโ€–โ€–๐‘†๐‘–๐‘›+1๐‘ฆ๐‘›โˆ’๐‘†๐‘›๐‘–๐‘ฆ๐‘›โ€–โ€–=0(3.59) and lim๐‘›โ†’โˆž๐‘†๐‘–๐‘›+1๐‘ฆ๐‘›=๐‘ข, that is, ๐‘†๐‘–๐‘‡๐‘›๐‘ฆ๐‘›โ†’๐‘ข. By the closeness of ๐‘†๐‘–, we have ๐‘†๐‘–๐‘ข=๐‘ข, forall๐‘–โ‰ฅ1. This implies that ๐‘ขโˆˆโˆฉโˆž๐‘–=1๐น(๐‘†๐‘–). Hence ๐‘ขโˆˆ(โˆฉโˆž๐‘–=1๐น(๐‘‡๐‘–))โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘†๐‘–)).
Next, we prove that ๐‘ขโˆˆโˆฉ๐‘๐‘–=1ฮฉ๐‘–. For any ๐‘โˆˆโ„ฑ, for each ๐‘–=1,2,โ€ฆ,๐‘, we have ๐œ™๎€ท๐‘ข๐‘–๐‘›,๐‘ง๐‘›๎€ธ๎€ทฮ˜=๐œ™๐‘–๐‘›๐‘ง๐‘›,๐‘ง๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘,๐‘ง๐‘›๎€ธ๎€ทโˆ’๐œ™๐‘,ฮ˜๐‘–๐‘›๐‘ง๐‘›๎€ธ๎€ท=๐œ™๐‘,๐‘ง๐‘›๎€ธ๎€ทโˆ’๐œ™๐‘,๐‘ข๐‘–๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘,๐‘ฅ๐‘›๎€ธ+๐œƒ๐‘›๎€ทโˆ’๐œ™๐‘,๐‘ข๐‘–๐‘›๎€ธโ†’0,as๐‘›โ†’โˆž.(3.60) It then yields that lim๐‘›โ†’โˆž(โ€–๐‘ข๐‘–๐‘›โ€–โˆ’โ€–๐‘ง๐‘›โ€–)=0. Since lim๐‘›โ†’โˆžโ€–๐‘ข๐‘–๐‘›โ€–=โ€–๐‘ขโ€–, forall๐‘–โ‰ฅ1, we have lim๐‘›โ†’โˆžโ€–โ€–๐‘ง๐‘›โ€–โ€–=โ€–๐‘ขโ€–.(3.61) Hence, lim๐‘›โ†’โˆžโ€–โ€–๐ฝ๐‘ง๐‘›โ€–โ€–=โ€–๐ฝ๐‘ขโ€–.(3.62) This together with lim๐‘›โ†’โˆžโ€–๐‘ข๐‘–๐‘›โ€–=โ€–๐‘ขโ€– show that for each ๐‘–=1,2,โ€ฆ,๐‘, lim๐‘›โ†’โˆžโ€–โ€–๐‘ข๐‘–๐‘›โˆ’๐‘ข๐‘›๐‘–โˆ’1โ€–โ€–=lim๐‘›โ†’โˆžโ€–โ€–๐ฝ๐‘ข๐‘–๐‘›โˆ’๐ฝ๐‘ข๐‘›๐‘–โˆ’1โ€–โ€–=0,(3.63) where ๐‘ข0๐‘›=๐‘ง๐‘›. On the other hand, we have ๐‘ข๐‘–๐‘›=๐พ๐‘“๐‘–,๐‘Ÿ๐‘–๐‘ข๐‘›๐‘–โˆ’1,foreach๐‘–=2,3,โ€ฆ,๐‘,(3.64) and ๐‘ข๐‘–๐‘› is a solution of the following variational equation ๐‘“๐‘–๎€ท๐‘ข๐‘–๐‘›๎€ธ+๎ซ๐ด,๐‘ฆ๐‘–๐‘ข๐‘–๐‘›,๐‘ฆโˆ’๐‘ข๐‘–๐‘›๎ฌ+๐œ“๐‘–(๐‘ฆ)โˆ’๐œ“๐‘–๎€ท๐‘ข๐‘–๐‘›๎€ธ+1๐‘Ÿ๐‘–๎ซ๐‘ฆโˆ’๐‘ข๐‘–๐‘›,๐ฝ๐‘ข๐‘–๐‘›โˆ’๐ฝ๐‘ข๐‘›๐‘–โˆ’1๎ฌโ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ.(3.65) By condition (A2), we note that ๎ซ๐ด๐‘–๐‘ข๐‘–๐‘›,๐‘ฆโˆ’๐‘ข๐‘–๐‘›๎ฌ+๐œ“๐‘–(๐‘ฆ)โˆ’๐œ“๐‘–๎€ท๐‘ข๐‘–๐‘›๎€ธ+1๐‘Ÿ๐‘–๎ซ๐‘ฆโˆ’๐‘ข๐‘–๐‘›,๐ฝ๐‘ข๐‘–๐‘›โˆ’๐ฝ๐‘ข๐‘›๐‘–โˆ’1๎ฌโ‰ฅโˆ’๐‘“๐‘–๎€ท๐‘ข๐‘–๐‘›๎€ธ,๐‘ฆโ‰ฅ๐‘“๐‘–๎€ท๐‘ฆ,๐‘ข๐‘–๐‘›๎€ธ,โˆ€๐‘ฆโˆˆ๐ถ.(3.66) By (A4), (3.63), and ๐‘ข๐‘–๐‘›โ†’๐‘ข for each ๐‘–=2,3,โ€ฆ,๐‘, we have โŸจ๐ด๐‘–๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐œ“๐‘–(๐‘ฆ)โˆ’๐œ“๐‘–(๐‘ข)โ‰ฅ๐‘“๐‘–(๐‘ฆ,๐‘ข),โˆ€๐‘ฆโˆˆ๐ถ.(3.67) For 0<๐‘ก<1 and ๐‘ฆโˆˆ๐ถ, define ๐‘ฆ๐‘ก=๐‘ก๐‘ฆ+(1โˆ’๐‘ก)๐‘ข. Noticing that ๐‘ฆ,๐‘ขโˆˆ๐ถ, we obtain ๐‘ฆ๐‘กโˆˆ๐ถ, which yields that โŸจ๐ด๐‘–๐‘ข,๐‘ฆ๐‘กโˆ’๐‘ขโŸฉ+๐œ“๐‘–๎€ท๐‘ฆ๐‘ก๎€ธโˆ’๐œ“๐‘–(๐‘ข)โ‰ฅ๐‘“๐‘–๎€ท๐‘ฆ๐‘ก๎€ธ,๐‘ข.(3.68) In view of the convexity of ๐œ™ it yields ๐‘กโŸจ๐ด๐‘–๎€ท๐œ“๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐‘ก๐‘–(๐‘ฆ)โˆ’๐œ“๐‘–๎€ธ(๐‘ข)โ‰ฅ๐‘“๐‘–๎€ท๐‘ฆ๐‘ก๎€ธ,๐‘ข.(3.69) It follows from (A1) and (A4) that 0=๐‘“๐‘–๎€ท๐‘ฆ๐‘ก,๐‘ฆ๐‘ก๎€ธโ‰ค๐‘ก๐‘“๐‘–๎€ท๐‘ฆ๐‘ก๎€ธ+,๐‘ฆ(1โˆ’๐‘ก)๐‘“๐‘–๎€ท๐‘ฆ๐‘ก๎€ธ,๐‘ขโ‰ค๐‘ก๐‘“๐‘–๎€ท๐‘ฆ๐‘ก๎€ธ๎€บ,๐‘ฆ+(1โˆ’๐‘ก)๐‘กโŸจ๐ด๐‘–๎€ท๐œ“๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐‘–(๐‘ฆ)โˆ’๐œ“๐‘–(.๐‘ข)๎€ธ๎€ป(3.70) Let ๐‘กโ†’0, from (A3), we obtain the following: ๐‘“i(๐‘ข,๐‘ฆ)+โŸจ๐ด๐‘–๐‘ข,๐‘ฆโˆ’๐‘ขโŸฉ+๐œ“๐‘–(๐‘ฆ)โˆ’๐œ“๐‘–(๐‘ข)โ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ,๐‘–=1,2,โ€ฆ,๐‘.(3.71) This implies that ๐‘ข is a solution of the system of generalized mixed equilibrium problem (3.2), that is, ๐‘ขโˆˆโˆฉ๐‘๐‘–=1ฮฉ๐‘–. Hence, ๐‘ขโˆˆโ„ฑโˆถ=(โˆฉ๐‘๐‘–=1ฮฉ๐‘–)โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘‡๐‘–))โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘†๐‘–)).
Finally, we show that ๐‘ฅ๐‘›โ†’๐‘ข=ฮ ๐น๐‘ฅ0. Indeed from ๐‘คโˆˆ๐นโŠ‚๐ถ๐‘› and ๐‘ฅ๐‘›=ฮ ๐ถ๐‘›๐‘ฅ0, we have the following: ๐œ™๎€ท๐‘ฅ๐‘›,๐‘ฅ0๎€ธ๎€ทโ‰ค๐œ™๐‘ค,๐‘ฅ0๎€ธ,โˆ€๐‘›โ‰ฅ0.(3.72) This implies that ๐œ™๎€ท๐‘ข,๐‘ฅ0๎€ธ=lim๐‘›โ†’โˆž๐œ™๎€ท๐‘ฅ๐‘›,๐‘ฅ0๎€ธ๎€ทโ‰ค๐œ™๐‘ค,๐‘ฅ0๎€ธ.(3.73) From the definition of ฮ ๐น๐‘ฅ0 and (3.73), we see that ๐‘ข=๐‘ค. This completes the proof.

Since every asymptotically relatively nonexpansive mappings is quasi-๐œ™-nonexpansive mappings, hence we obtain the following corollary.

Corollary 3.2. Let ๐ธ be a uniformly convex and uniformly smooth Banach space, let ๐ถ be a nonempty, closed, and convex subset of ๐ธ. Let ๐ด๐‘–โˆถ๐ถโ†’๐ธโˆ— be a continuous and monotone mapping, ๐œ“๐‘–โˆถ๐ถโ†’โ„ be a lower semi-continuous and convex function, ๐‘“๐‘– be a bifunction from ๐ถร—๐ถ to โ„ satisfying (A1)โ€“(A4), ๐พ๐‘“๐‘–,๐‘Ÿ๐‘– is the mapping defined by (2.10) where ๐‘Ÿ๐‘–โ‰ฅ๐‘Ÿ>0, and let {๐‘‡๐‘–}โˆž๐‘–=1, {๐‘†๐‘–}โˆž๐‘–=1 be countable families of closed and quasi-๐œ™-nonexpansive mapping such that โ„ฑโˆถ=(โˆฉ๐‘๐‘–=1ฮฉ๐‘–)โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘‡๐‘–))โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘†๐‘–))โ‰ โˆ…. Let {๐‘ฅ๐‘›} be a sequence generated by ๐‘ฅ0โˆˆ๐ถ and ๐ถ0=๐ถ, such that ๐‘ฆ๐‘›=๐ฝโˆ’1๎ƒฉ๐›ฝ๐‘›,0๐ฝ๎€ท๐‘ฅ๐‘›๎€ธ+โˆž๎“๐‘–=1๐›ฝ๐‘›,๐‘–๐ฝ๎€ท๐‘‡๐‘–๐‘ฅ๐‘›๎€ธ๎ƒช,๐‘ง๐‘›=๐ฝโˆ’1๎ƒฉ๐›ผ๐‘›,0๐ฝ๎€ท๐‘ฅ๐‘›๎€ธ+โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–๐ฝ๎€ท๐‘†๐‘–๐‘ฆ๐‘›๎€ธ๎ƒช,๐‘ข๐‘›(๐‘–)=๐พ๐‘“๐‘–,๐‘Ÿ๐‘–๐พ๐‘“๐‘–โˆ’1,๐‘Ÿ๐‘–โˆ’1โ‹ฏ๐พ๐‘“1,๐‘Ÿ1๎€ท๐‘ง๐‘›๎€ธ๐ถ,๐‘–=1,2,โ€ฆ,๐‘,๐‘›+1=๎‚ป๐‘งโˆˆ๐ถ๐‘›โˆถmax๐‘–=1,2,โ€ฆ,๐‘๐œ™๎‚€๐‘ง,๐‘ข๐‘›(๐‘–)๎‚๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ๎€ท,๐œ™๐‘ง,๐‘ฆ๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ๎‚ผ,๐‘ฅ๐‘›+1=ฮ ๐ถ๐‘›+1๐‘ฅ0,โˆ€๐‘›โ‰ฅ0,(3.74) where ฮ ๐ถ is the generalized projection from ๐ธ onto ๐ถ, ๐ฝ is the duality mapping on ๐ธ. The coefficient sequences {๐›ผ๐‘›,๐‘–} and {๐›ฝ๐‘›,๐‘–}โŠ‚[0,1], satisfying: (i)โˆ‘โˆž๐‘–=0๐›ผ๐‘›,i=1; (ii)โˆ‘โˆž๐‘–=0๐›ฝ๐‘›,๐‘–=1; (iii)liminf๐‘›โ†’โˆž๐›ผ๐‘›,0๐›ผ๐‘›,๐‘–>0, forall๐‘–โ‰ฅ1; (iv)liminf๐‘›โ†’โˆž๐›ฝ๐‘›,0๐›ฝ๐‘›,๐‘–>0, forall๐‘–โ‰ฅ1. ฮฉ๐‘–,๐‘–=1,2,โ€ฆ,๐‘ is the set of solutions to the following generalized mixed equilibrium problem: ๐‘“๐‘–(๐‘ง,๐‘ฆ)+โŸจ๐ด๐‘–๐‘ง,๐‘ฆโˆ’๐‘งโŸฉ+๐œ“๐‘–(๐‘ฆ)โˆ’๐œ“๐‘–(๐‘ง)โ‰ฅ0,โˆ€๐‘ฆโˆˆ๐ถ,๐‘–=1,2,โ€ฆ,๐‘.(3.75) Then the sequence {๐‘ฅ๐‘›} converges strongly to ฮ โ„ฑ๐‘ฅ0.

If ๐ด๐‘–=๐ด,๐œ“๐‘–=๐œ“, and ๐‘“๐‘–=๐‘“ for all ๐‘–โ‰ฅ1 in Theorem 3.1, we obtain the following corollary.

Corollary 3.3. Let ๐ธ be a uniformly smooth and uniformly convex Banach space, let ๐ถ be a nonempty, closed, and convex subset of ๐ธ. Let ๐ดโˆถ๐ถโ†’๐ธโˆ— be a continuous and monotone mapping, ๐œ“โˆถ๐ถโ†’โ„ be a lower semicontinuous and convex function, ๐‘“ be a bifunction from ๐ถร—๐ถ to โ„ satisfying (A1)โ€“(A4), ๐พ๐‘“,๐‘Ÿ be the mapping define by (2.10) where ๐‘Ÿ>0, and let {๐‘‡๐‘–}โˆž๐‘–=1, {๐‘†๐‘–}โˆž๐‘–=1 be countable families of closed and uniformly ๐ฟ๐‘–, ๐œ‡๐‘–-Lipschitz continuous, and asymptotically relatively nonexpansive mappings with sequence {๐‘˜๐‘›},{๐œ๐‘›}โŠ‚[1,โˆž);โ€‰โ€‰๐‘˜๐‘›โ†’1,๐œ๐‘›โ†’1 such that โ„ฑโˆถ=ฮฉโˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘‡๐‘–))โˆฉ(โˆฉโˆž๐‘–=1๐น(๐‘†๐‘–))โ‰ โˆ…. Let {๐‘ฅ๐‘›} be a sequence generated by ๐‘ฅ0โˆˆ๐ถ and ๐ถ0=๐ถ, such that ๐‘ฆ๐‘›=๐ฝโˆ’1๎ƒฉ๐›ฝ๐‘›,0๐ฝ๎€ท๐‘ฅ๐‘›๎€ธ+โˆž๎“๐‘–=1๐›ฝ๐‘›,๐‘–๐ฝ๎€ท๐‘‡๐‘›๐‘–๐‘ฅ๐‘›๎€ธ๎ƒช,๐‘ง๐‘›=๐ฝโˆ’1๎ƒฉ๐›ผ๐‘›,0๐ฝ๎€ท๐‘ฅ๐‘›๎€ธ+โˆž๎“๐‘–=1๐›ผ๐‘›,๐‘–๐ฝ๎€ท๐‘†๐‘›๐‘–๐‘ฆ๐‘›๎€ธ๎ƒช,๐‘ข๐‘›=๐พ๐‘“,๐‘Ÿ๐‘ง๐‘›,๐ถ๐‘›+1=๎‚ป๐‘งโˆˆ๐ถ๐‘›โˆถmax๐‘–=1,2,โ€ฆ,๐‘๐œ™๎‚€๐‘ง,๐‘ข๐‘›(๐‘–)๎‚๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ+๐œƒ๐‘›๎€ท,๐œ™๐‘ง,๐‘ฆ๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›๎‚ผ,๐‘ฅ๐‘›+1=ฮ ๐ถ๐‘›+1๐‘ฅ0,โˆ€๐‘›โ‰ฅ0,(3.76) where ๐œ‰๐‘›=sup๐‘โˆˆโ„ฑ(๐‘˜๐‘›โˆ’1)๐œ™(๐‘,๐‘ฅ๐‘›), ๐œƒ๐‘›=๐›ฟ๐‘›+๐œ‰๐‘›๐œ๐‘›, and ๐›ฟ๐‘›=sup๐‘โˆˆโ„ฑ(๐œ๐‘›โˆ’1)๐œ™(๐‘,๐‘ฅ๐‘›). The coefficient sequences {๐›ผ๐‘›,๐‘–} and {๐›ฝ๐‘›,๐‘–}โŠ‚[0,1], satisfying: (i)โˆ‘โˆž๐‘–=0๐›ผ๐‘›,๐‘–=1; (ii)โˆ‘โˆž๐‘–=0๐›ฝ๐‘›,๐‘–=1; (iii)liminf๐‘›โ†’โˆž๐›ผ๐‘›,0๐›ผ๐‘›,๐‘–>0, forall๐‘–โ‰ฅ1; (iv)liminf๐‘›โ†’โˆž๐›ฝ๐‘›,0๐›ฝ๐‘›,๐‘–>0, forall๐‘–โ‰ฅ1. Then the sequence {๐‘ฅ๐‘›} converges strongly to ฮ โ„ฑ๐‘ฅ0.

If ๐‘–=1 in Theorem 3.1, then we obtain the following corollary.

Corollary 3.4. Let ๐ธ be a uniformly smooth and uniformly convex Banach space, let ๐ถ be a nonempty, closed, and convex subset of ๐ธ. Let ๐ดโˆถ๐ถโ†’๐ธโˆ— be a continuous and monotone mapping, ๐œ“โˆถ๐ถโ†’โ„ be a lower semicontinuous and convex function, ๐‘“ be a bifunction from ๐ถร—๐ถ to โ„ satisfying (A1)โ€“(A4), ๐พ๐‘“,๐‘Ÿ is the mapping define by (2.10) where ๐‘Ÿ>0, and let ๐‘‡,๐‘† are two closed and uniformly ๐ฟ, ๐œ‡-Lipschitz continuous and asymptotically relatively nonexpansive mappings with sequence {๐‘˜๐‘›},{๐œ๐‘›}โŠ‚[1,โˆž);โ€‰โ€‰๐‘˜๐‘›โ†’1,๐œ๐‘›โ†’1 such that โ„ฑโˆถ=ฮฉโˆฉ๐น(๐‘‡)โˆฉ๐น(๐‘†)โ‰ โˆ…. Let {๐‘ฅ๐‘›} be a sequence generated by ๐‘ฅ0โˆˆ๐ถ and ๐ถ0=๐ถ, we have๐‘ฆ๐‘›=๐ฝโˆ’1๎€ท๐›ฝ๐‘›๐ฝ๐‘ฅ๐‘›+๎€ท1โˆ’๐›ฝ๐‘›๎€ธ๐ฝ๐‘‡๐‘›๐‘ฅ๐‘›๎€ธ,๐‘ง๐‘›=๐ฝโˆ’1๎€ท๐›ผ๐‘›๐ฝ๐‘ฅ๐‘›+๎€ท1โˆ’๐›ผ๐‘›๎€ธ๐ฝ๐‘†๐‘›๐‘ฆ๐‘›๎€ธ,๐‘ข๐‘›=๐พ๐‘“,๐‘Ÿ๐‘ง๐‘›,๐ถ๐‘›+1=๎€ฝ๐‘งโˆˆ๐ถ๐‘›๎€ทโˆถ๐œ™๐‘ง,๐‘ข๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ+๐œƒ๐‘›๎€ท,๐œ™๐‘ง,๐‘ฆ๐‘›๎€ธ๎€ทโ‰ค๐œ™๐‘ง,๐‘ฅ๐‘›๎€ธ+๐œ‰๐‘›๎€พ,๐‘ฅ๐‘›+1=ฮ ๐ถ๐‘›+1๐‘ฅ0,โˆ€๐‘›โ‰ฅ0,(3.77) where ๐œ‰๐‘›=sup๐‘โˆˆโ„ฑ(๐‘˜๐‘›โˆ’1)๐œ™(๐‘,๐‘ฅ๐‘›), ๐œƒ๐‘›=๐›ฟ๐‘›+๐œ‰๐‘›๐œ๐‘›, and ๐›ฟ๐‘›=sup๐‘โˆˆโ„ฑ(๐œ๐‘›โˆ’1)๐œ™(๐‘,๐‘ฅ๐‘›). The coefficient sequences {๐›ผ๐‘›} and {๐›ฝ๐‘›}โŠ‚[0,1], satisfying (D1)liminf๐‘›โ†’โˆž๐›ผ๐‘›(1โˆ’๐›ผ๐‘›)>0; (D2)liminf๐‘›โ†’โˆž๐›ฝ๐‘›(1โˆ’๐›ฝ๐‘›)>0. Then the sequence {๐‘ฅ๐‘›} converges strongly to ฮ โ„ฑ๐‘ฅ0.

Remark 3.5. Theorem 3.1 and Corollary 3.3 improve and extend the corresponding results of Petrot et al. [24], Kumam and Wattanawitoon [25], and Chang et al. [26] in the following senses: (i)for the mappings, we extend the mappings from nonexpansive mappings, hemirelatively nonexpansive mappings to two infinite family of closed asymptotically relatively nonexpansive mappings; (ii)from a solution of the classical equilibrium problem to a system of generalized mixed equilibrium problems and the generalized mixed equilibrium problem with an infinite family of closed relatively nonexpansive mappings.

Remark 3.6. Corollary 3.4 improves and extends the corresponding results of Theorem 3.1 in Kumam and Wattanawitoon [25] and Corollary 3.3 in Saewan et al. [11] in the following senses:(i)the mapping in [11] and [25] (ii)the conditions (D1) and (D2) of the parameters {๐›ผ๐‘›} and {๐›ฝ๐‘›} are weaker and not complicated than the conditions (C1)โ€“(C3) in [[25], Theoremโ€‰โ€‰3.1] and [[11], Theoremโ€‰โ€‰3.1] which are easy to compute.

Acknowledgments

This first author was supported by The Hands-On Research and Development, Rajamangala University of Technology Lanna (Grant no. UR2L003). Moreover, this work was supported by the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission (NRU-CSEC Grant no. 55000613).