Convergence theorems for asymptotically nonexpansive mappings in Banach spaces
Acta mathematica Universitatis Comenianae, Tome 77 (2008) no. 1
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Let E be a uniformly convex Banach space, and let K be a nonempty convex closed subset which is also a nonexpansive retract of E . Let T : K ® E be an asymptotically nonexpansive mapping with { kn } Ì [1, ¥ ) such that ( å from n =1 to ¥ ) ( kn - 1) < ¥ and let F ( T ) be nonempty, where F ( T ) denotes the fixed points set of T . Let {a n } , {b n } , {g n } , {a¢ n } , {b¢ n } , {g¢ n } , {a¢¢ n } , {b¢¢ n } and {g¢¢ n } be real sequences in [0, 1] such that a n + b n + g n = a¢ n + b¢ n + g¢ n = a¢¢ n + b¢¢ n + g¢¢ n = 1 and e £ a n , a¢ n , a¢¢ n £ 1 - e for all n Î N and some e > 0 , starting with arbitrary x 1 Î K , define the sequence { xn } by setting zn = P ( a¢¢ n T ( PT ) n-1 xn + b¢¢ n xn + g¢¢ n wn ), yn = P ( a¢ n T ( PT ) n-1 zn + b¢ n xn + g¢ n vn ), x n+1 = P ( a n T ( PT ) n-1 yn + b n xn + g n un ), with the restrictions ( å from n =1 to ¥ ) ( g n ) < ¥ , ( å from n =1 to ¥ ) ( g¢ n ) < ¥ and ( å from n =1 to ¥ ) ( g¢¢ n ) < ¥ where { wn } , { vn } and { un } are bounded sequences in K . (i) If E is real uniformly convex Banach space satisfying Opial's condition, then weak convergence of { xn } to some p Î F ( T ) is obtained; (ii) If T satisfies condition (A), then { xn } convergence strongly to some p Î F ( T ).