Approximation Methods for Common Fixed Points of Mean Nonexpansive Mapping in Banach Spaces
© Z. Gu and Y. Li. 2008
Received: 17 October 2007
Accepted: 2 January 2008
Published: 15 January 2008
Let be a uniformly convex Banach space, and let be a pair of mean nonexpansive mappings. In this paper, it is proved that the sequence of Ishikawa iterations associated with and converges to the common fixed point of and .
1. Introduction and Preliminaries
for all , , .
where , . The recursion formulas (1.2) were first introduced in 1994 by Rashwan and Saddeek  in the framework of Hilbert spaces.
In recent years, several authors (see [2–6]) have studied the convergence of iterations to a common fixed point for a pair of mappings. Rashwan has studied the convergence of Mann iterations to a common fixed point (see ) and proved that the Ishikawa iterations converge to a unique common fixed point in Hilbert spaces (see ). Recently, Ćirić has proved that if the sequence of Ishikawa iterations sequence associated with and converges to , then is the common fixed point of and (see ). In [4, 6], the authors studied the same problem. In , Bose defined the pair of mean nonexpansive mappings, and proved the existence of the fixed point in Banach spaces. In particular, he proved the following theorem.
Theorem 1.1 ().
and have a common fixed point ;
- (ii)further, if , then
is the unique common fixed point and unique as a fixed point of each and ,
the sequence defined by , for any , converges strongly to .
It is our purpose in this paper to consider an iterative scheme, which converges to a common fixed point of the pair of mean nonexpansive mappings. Theorem 2.1 extends and improves the corresponding results in .
2. Main Results
Now we prove the following theorem which is the main result of this paper.
Let be a uniformly convex Banach space, and are a pair of mean nonexpansive with a nonempty common fixed points set; if , then the Ishikawa sequence converges to the common fixed point of and .
Let , by , it is easy to see that , thus and .
Hence, is bounded.
for every with . It is easy to see that Banach space is uniformly convex if and only if for any implies .
we know is bounded, then there exists , such that . Thus, .
Let , then we have . It is a contradiction. Hence, .
Similarly, we can prove that . So is the common fixed point of and .
So it is easy to see that . Thus, , that is is a Cauchy sequence. Hence, there exists , such that . We know that and is the common fixed point of and . This completes the proof of the theorem.
The work was partially supported by the Emphases Natural Science Foundation of Guangdong Institution of Higher Learning, College and University (no. 05Z026).
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