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Journal of Function Spaces

Volume 2014 (2014), Article ID 684191, 8 pages

http://dx.doi.org/10.1155/2014/684191

## Some Convergence and Stability Results for Two New Kirk Type Hybrid Fixed Point Iterative Algorithms

^{1}Department of Mathematics, Yıldız Technical University, Davutpasa Campus, Esenler, 34220 Istanbul, Turkey^{2}Department of Mathematical Engineering, Yıldız Technical University, Davutpasa Campus, Esenler, 34210 Istanbul, Turkey

Received 13 September 2013; Accepted 13 November 2013; Published 28 January 2014

Academic Editor: M. Mursaleen

Copyright © 2014 Faik Gürsoy and Vatan Karakaya. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

We introduce Kirk-multistep-SP and Kirk-S iterative algorithms and we prove some convergence and stability results for these iterative algorithms. Since these iterative algorithms are more general than some other iterative algorithms in the existing literature, our results generalize and unify some other results in the literature.

#### 1. Introduction and Preliminaries

Fixed point theory has an important role in the study of nonlinear phenomena. This theory has been applied in a wide range of disciplines in various areas such as science, technology, and economics; see, for example, [1–5]. The importance of this theory has attracted researchers’ interest, and consequently numerous fixed point theorems have been put forward; see, for example, [6–17] and the references included therein. In this highly dynamic area, one of the most celebrated theorems amongst hundreds is Banach fixed point theorem (also known as the contraction mapping theorem or contraction mapping principle) [7]. An important process which is called iteration method arises naturally during proving of this theorem. A fixed point iteration method is given by a general form as follows: where is an ambient space, is an arbitrary initial point, is an operator, and is some function. For example, if in (1), then we obtain well-known Picard iteration [18] as follows:

Iterative methods are important instruments commonly used in the study of fixed point theory. These powerful and useful tools enable us to find solutions for a wide variety of problems that arise in many branches of the above mentioned areas. This is a reason, among a number of reasons, why researchers are seeking new iteration methods or trying to improve existing methods over the years. In this respect, it is not surprising to see a number of papers dealing with the study of iterative methods to investigate various important themes; see, for example, [19–27].

The purpose of this paper is to introduce two new Kirk type hybrid iteration methods and to show that these iterative methods can be used to approximate fixed points of certain class of contractive operators. Furthermore, we prove that these iterative methods are stable with respect to the same class of contractive operators.

As a background to our exposition, we describe some iteration schemes and contractive type mappings.

The following multistep-SP iteration was employed in [20, 28]: where denotes the set of all nonnegative integers, including zero, and , , , and , , , are real sequences in satisfying certain conditions.

By taking and in (3) we obtain SP [25] and two-step Mann [27] iterative schemes, respectively. In (3), if we take with and with , (const.), then we get the iterative procedures introduced in [23, 29], which are commonly known as the Mann and Krasnoselskij iterations, respectively. The Krasnoselskij iteration [29] reduces to the Picard iteration [18] for .

A sequence defined by is known as the S iteration process [6, 19].

Continuing the above trend, we will introduce and employ the following iterative schemes which are called Kirk-multistep-SP and Kirk-S iterations, respectively: where , for ; , are sequences in satisfying , , , and for ; and , for are fixed integers with .

By taking , , and with in (5) we obtain the Kirk-SP [30], a Kirk-two-step-Mann, and the Kirk-Mann [31] iterative schemes, respectively. Also, (5) gives the usual Kirk iterative process [32] for , with and . If we put and , in (5) and (6), then we have the usual multistep-SP iteration (3) and S iteration (4), respectively, with , , , , . The SP iteration [25], the two-step Mann iteration [27], the Mann iteration [23], the Krasnoselskij iteration [29], and the Picard iteration [18] schemes are special cases of the multistep-SP iterative scheme (3), as explained above. So we conclude that these are also special cases of the Kirk-multistep-SP iterative scheme (5).

We end this section with some definitions and lemmas which will be useful in proving our main results.

*Definition 1 (see [33]). *Let be a normed space. A mapping is called contractive-like mapping if there exists such that
where is a monotone increasing function with .

*Remark 2. *By taking in (7), one can get contractive definition due to Osilike and Udomene [34]. Also, by putting in (7), condition (7) reduces to the contractive definition in [35]. In [35] it was shown that the class of these operators is wider than class of Zamfirescu operators given in [17], where , and , , and are real numbers satisfying , , and .

*Remark 3 (see [20, 28]). *A map satisfying (7) need not have a fixed point. However, using (7), it is obvious that if has a fixed point, then it is unique.

*Definition 4 (see [36, 37]). *Let be a normed space, a mapping, and an iterative sequence generated by the iterative process (1) with limit point . Let be an arbitrary sequence in and set
We will say that the iterative sequence is -stable or stable with respect to if and only if

Lemma 5 (see [8]). *If is a real number such that and is a sequence of nonnegative numbers such that , then, for any sequence of positive numbers satisfying
**
one has .*

Lemma 6 (see [31]). *Let be a normed linear space and let be a self-map of satisfying (7). Let be a subadditive, monotone increasing function such that , , , . Then, for all , and for all **
where .*

#### 2. Main Results

For simplicity we assume in the following four theorems that is a normed linear space, is a self map of satisfying the contractive condition (7) with some fixed point , and is a subadditive monotone increasing function such that and , , .

Theorem 7. *Let be a sequence generated by the Kirk-multistep-SP iterative scheme (5). Then the iterative sequence converges strongly to .*

*Proof. *The uniqueness of follows from (7). We will now prove that .

Using Kirk-multistep-SP iterative process (5), condition (7), and Lemma 6, we get
By combining (12), (13), and (14) we obtain
Continuing the above process we have
Using again Kirk-multistep-SP iterative process (5), condition (7), and Lemma 6, we have
Substituting (17) into (16) we derive
Since and , for , then
Hence, by an application of Lemma 5 to the inequality (18), we get .

Theorem 8. *Let be a sequence generated by the Kirk-multistep-SP iterative scheme (5). Then, the iterative sequence is -stable.*

*Proof. *Let , , for , be arbitrary sequences in . Let , , where , , , , and let . Now we will prove that .

It follows from (5) and Lemma 6 that
Combining (20), (21), and (22) we get
By induction

Again using (5) and Lemma 6 we have
Substituting (25) into (24) we derive
Define
We now show that . Since , , , and for , we have
Therefore, an application of Lemma 5 to (26) yields .

Now suppose that . Then, we will show that .

Using Lemma 6 we have
Combining (29), (30), and (31) we obtain
Thus, by induction, we get
Again using (5) and Lemma 6 we have
Substituting (34) into (33) we derive
Again define
Using the same argument as that of the first part of the proof we obtain .

Hence (35) becomes
It therefore follows from assumption that as .

Theorem 9. *Let be a sequence generated by the Kirk-S iterative scheme (6). Then, the iterative sequence converges strongly to .*

*Proof. *The uniqueness of follows from (7). We will now prove that .

Using Kirk-S iterative process (6), condition (7), and Lemma 6, we get
Substituting (39) into (38) we obtain
Since and with , ,
Utilizing (41) and Lemma 5, (40) yields .

Theorem 10. *Let be a sequence generated by the Kirk-S iterative scheme (6). Then, the iterative sequence is -stable.*

*Proof. *Let , , , and . Assume that . Now we will prove that .

It follows from (6) and Lemma 6 that
Combining (42) and (43) we have
Define
We now show that . Since , , , and , we obtain
Thus, (44) becomes
Therefore, an application of Lemma 5 to (47) leads to .

Now suppose that . Then, we will show that .

Using Lemma 6 we have
Substituting (49) into (48) we get
Again define
Using the same argument as that of the first part of the proof we obtain .

Hence (50) becomes
It therefore follows from assumption that as .

*Remark 11. *Theorem 7 is a generalization and extension of Theorem 2.1 of [38], Theorem 2.1 of [39], Theorem 1 of [20], and Theorem 2.4 of [30]. Theorems 8 is a generalization and extension of Theorem 3.6 of [38] and Theorem 3 of [40]. Theorem 9 is a generalization and extension of Theorem 8 of [41] and Theorem 3 of [20].

#### Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

#### Acknowledgment

This research has been supported by Yıldız Technical University Scientific Research Projects Coordination Department, Project no. BAPK 2012-07-03-DOP02.

#### References

- K. C. Border,
*Fixed Point Theorems with Applications to Economics and Game Theory*, Cambridge University Press, Cambridge, UK, 1985. - M. Droste, W. Kuich, and H. Vogler, Eds.,
*Handbook of Weighted Automata. EATCS Mono-Graphs in Theoretical Computer Science*, Springer, Berlin, Germany, 2009. - E. A. Ok,
*Real Analysis with Economic Applications*, Princeton University Press, Princeton, NJ, USA, 2007. - N. Radde, “Fixed point characterization of biological networks with complex graph topology,”
*Bioinformatics*, vol. 26, no. 22, Article ID btq517, pp. 2874–2880, 2010. View at Publisher · View at Google Scholar · View at Scopus - G. Q. Wang and S. S. Cheng, “Fixed point theorems arising from seeking steady states of neural networks,”
*Applied Mathematical Modelling*, vol. 33, no. 1, pp. 499–506, 2009. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at Scopus - R. P. Agarwal, D. O'Regan, and D. R. Sahu,
*Fixed Point Theory for Lipschitzian Type-Mappings with Applications*, Springer, New York, NY, USA, 2009. - S. Banach, “Sur les opérations dans les ensembles abstraits et leur application aux équations intégrales,”
*Fundamenta Mathematicae*, vol. 3, pp. 133–181, 1922. - V. Berinde,
*Iterative Approximation of Fixed Points*, Springer, Berlin, Germany, 2007. - S. K. Chatterjea, “Fixed point theorems,”
*Comptes Rendus de l'Academie Bulgare des Sciences*, vol. 25, pp. 727–730, 1972. - L. B. Ciric, “A generalization of Banach's contraction principle,”
*Proceedings of the American Mathematical Society*, vol. 45, pp. 267–273, 1974. - M. Ertürk and V. Karakaya, “
*n*-tuplet fixed point theorems for contractive type mappings in partially ordered metric spaces,”*Journal of Inequalities and Applications*, vol. 2013, p. 196, 2013. View at Publisher · View at Google Scholar - R. Kannan, “Some results on fixed points,”
*Bulletin of Calcutta Mathematical Society*, vol. 60, pp. 71–76, 1968. - M. A. Khamsi and W. A. Kirk,
*An Introduction to Metric Spaces and Fixed Point Theory*, PAAM Monographs in Pure and Applied Mathematics, Wiley, New York, NY, USA, 2001. - M. Mursaleen, S. A. Mohiuddine, and R. P. Agarwal, “Corrigendum to ‘coupled fixed point theorems for $\alpha -\psi $-contractive type mappings in partially ordered metric spaces’,”
*Fixed Point Theory and Applications*, vol. 2013, p. 127, 2013. View at Publisher · View at Google Scholar - M. Mursaleen, S. A. Mohiuddine, and R. P. Agarwal, “Coupled fixed point theorems for $\alpha -\psi $-contractive type mappings in partially ordered metric spaces,”
*Fixed Point Theory and Applications*, vol. 2012, p. 228, 2012. View at Publisher · View at Google Scholar - R. Saadati, S. M. Vaezpour, P. Vetro, and B. E. Rhoades, “Fixed point theorems in generalized partially ordered G-metric spaces,”
*Mathematical and Computer Modelling*, vol. 52, no. 5-6, pp. 797–801, 2010. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at Scopus - T. Zamfirescu, “Fix point theorems in metric spaces,”
*Archiv der Mathematik*, vol. 23, no. 1, pp. 292–298, 1972. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at Scopus - E. Picard, “Memoire sur la theorie des equations aux derivees partielles et la methode des approximations successives,”
*Journal de Mathématiques Pures et Appliquées*, vol. 6, pp. 145–210, 1890. - R. P. Agarwal, D. O'Regan, and D. R. Sahu, “Iterative construction of fixed points of nearly asymp- totically nonexpansive mappings,”
*Journal of Nonlinear and Convex Analysis*, vol. 8, no. 1, pp. 61–79, 2007. - F. Gürsoy, V. Karakaya, and B. E. Rhoades, “Data dependence results of new multistep and S-iterative schemes for contractive-like operators,”
*Fixed Point Theory and Applications*, vol. 2013, p. 76, 2013. View at Publisher · View at Google Scholar - S. Ishikawa, “Fixed points by a new iteration method,”
*Proceedings of the American Mathematical Society*, vol. 44, pp. 147–150, 1974. - V. Karakaya, F. Gürsoy, K. Dogan, and M. Ertürk, “Data dependence results for multistep and CR iterative schemes in the class of contractive-like operators,”
*Abstract and Applied Analysis*, vol. 2013, Article ID 381980, 7 pages, 2013. View at Publisher · View at Google Scholar - W. R. Mann, “Mean value methods in iterations,”
*Proceedings of the American Mathematical Society*, vol. 4, pp. 506–510, 1953. - M. A. Noor, “New approximation schemes for general variational inequalities,”
*Journal of Mathematical Analysis and Applications*, vol. 251, no. 1, pp. 217–229, 2000. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at Scopus - W. Phuengrattana and S. Suantai, “On the rate of convergence of Mann, Ishikawa, Noor and SP-iterations for continuous functions on an arbitrary interval,”
*Journal of Computational and Applied Mathematics*, vol. 235, no. 9, pp. 3006–3014, 2011. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at Scopus - B. E. Rhoades and S. M. Soltuz, “The equivalence between Mann-Ishikawa iterations and multistep iteration,”
*Nonlinear Analysis, Theory, Methods and Applications*, vol. 58, no. 1-2, pp. 219–228, 2004. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at Scopus - S. Thianwan, “Common fixed points of new iterations for two asymptotically nonexpansive nonself-mappings in a Banach space,”
*Journal of Computational and Applied Mathematics*, vol. 224, no. 2, pp. 688–695, 2009. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at Scopus - F. Gürsoy, V. Karakaya, and B. E. Rhoades, “The equivalence among new multistep iteration, S-iteration and some other iterative schemes,” http://arxiv.org/abs/1211.5701. In press.
- M. A. Krasnoselkij, “Two remarks on the method of successive approximations,”
*Uspehi Matematicheskih Nauk*, vol. 63, no. 1, pp. 123–127, 1955. - N. Hussain, R. Chugh, V. Kumar, and A. Rafiq, “On the rate of convergence of Kirk-type iterative schemes,”
*Journal of Applied Mathematics*, vol. 2012, Article ID 526503, 22 pages, 2012. View at Publisher · View at Google Scholar - M. O. Olatinwo, “Some stability results for two hybrid fixed point iterative algorithms in normed linear space,”
*Matematicki Vesnik*, vol. 61, no. 4, pp. 247–256, 2009. View at Scopus - W. A. Kirk, “On successive approximations for nonexpansive mappings in Banach spaces,”
*Glasgow Mathematical Journal*, vol. 12, pp. 6–9, 1971. - C. O. Imoru and M. O. Olatinwo, “On the stability of Picard and Mann iteration processes,”
*Carpathian Journal of Mathematics*, vol. 19, no. 2, pp. 155–160, 2003. View at Zentralblatt MATH · View at Scopus - M. O. Osilike and A. Udomene, “Short proofs of stability results for fixed point iteration procedures for a class of contractive-type mappings,”
*Indian Journal of Pure and Applied Mathematics*, vol. 30, no. 12, pp. 1229–1234, 1999. View at Zentralblatt MATH · View at Scopus - V. Berinde, “On the convergence of the Ishikawa iteration in the class of quasi contractive operators,”
*Acta Mathematica Universitatis Comenianae*, vol. 73, no. 1, pp. 119–126, 2004. View at Zentralblatt MATH · View at Scopus - A. M. Harder and T. L. Hicks, “A stable iteration procedure for nonexpansive mappings,”
*Mathematica Japonica*, vol. 33, pp. 687–692, 1988. - A. M. Harder and T. L. Hicks, “Stability results for fixed point iteration procedures,”
*Mathematica Japonica*, vol. 33, pp. 693–706, 1988. - İ. Yıldırım, M. Özdemir, and H. Kızıltunç, “On the convergence of a new two-step iteration in the class of quasi-contractive operators,”
*International Journal of Mathematical Analysis*, vol. 3, pp. 1881–1892, 2009. - R. Chugh and V. Kumar, “Strong convergence of SP iterative scheme for quasi-contractive operators in Banach spaces,”
*International Journal of Applied Mathematics and Computer Science*, vol. 31, pp. 21–27, 2011. - F. Gürsoy, V. Karakaya, and B. E. Rhoades, “Some convergence and stability results for the Kirk multistep and Kirk-Sp fixed point iterative algorithms,”
*Abstract and Applied Analysis*, 2013. - N. Hussain, A. Rafiq, B. Damjanovic, and R. Lazovic, “On rate of convergence of various iterative schemes,”
*Fixed Point Theory and Applications*, vol. 2011, p. 45, 2011. View at Publisher · View at Google Scholar