Abstract and Applied Analysis

Volume 2013, Article ID 879084, 7 pages

http://dx.doi.org/10.1155/2013/879084

## Common Fixed Points for Weak *ψ*-Contractive Mappings in Ordered Metric Spaces with Applications

^{1}Department of Mathematics, Khalsa College of Engineering & Technology (Punjab Technical University), Ranjit Avenue, Amritsar 143001, India^{2}Faculty of Applied Sciences, University Politehnica of Bucharest, 313 Splaiul Independentei, 060042 Bucharest, Romania

Received 7 July 2013; Accepted 29 August 2013

Academic Editor: Lishan Liu

Copyright © 2013 Sumit Chandok and Simona Dinu. 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 obtain some new common fixed point theorems satisfying a weak contractive condition in the framework of partially ordered metric spaces. The main result generalizes and extends some known results given by some authors in the literature.

#### 1. Introduction and Preliminaries

Fixed point and common fixed point theorems for different types of nonlinear contractive mappings have been investigated extensively by various researchers (see [1–41]). Fixed point problems involving weak contractions and the mappings satisfying weak contractive type inequalities have been studied by many authors (see [10–20] and references cited therein).

Recently, many researchers have obtained fixed point, common fixed point, coupled fixed point, and coupled common fixed point results in partially ordered metric spaces (see [3, 6–8, 10–12, 29, 30, 32, 36]) and other spaces (see [5, 15, 31, 35, 38, 40, 41]).

Let be a partially ordered set and two self-mappings on . A pair of self-mappings of is said to be *weakly increasing* [4] if and for any . An ordered pair is said to be *partially weakly increasing* if for all .

Note that a pair is weakly increasing if and only if the ordered pairs and are partially weakly increasing.

*Example 1 (see [3]). * Let be endowed with usual ordering and two mappings given by and . Clearly, the pair is partially weakly increasing. But for any implies that the pair is not partially weakly increasing.

Let be a partially ordered set. A mapping is called a *weak annihilator* of a mapping if for all .

*Example 2 (see [3]). * Let be endowed with usual ordering and be two mappings given by and . It is clear that for implies that is a weak annihilator of .

Let be a partially ordered set. A mapping is called a * dominating* if for any .

*Example 3 (see [3]). *Let be endowed with usual ordering and a mapping defined by , since for implies that is a dominating mapping.

A subset of a partially ordered set is said to be *well ordered* if every two elements of are comparable.

Let be a nonempty subset of a metric space . Let and be mappings from a metric space into itself. A point is a *common fixed (resp., coincidence) point* of and if . The set of fixed points (resp., coincidence points) of and is denoted by (resp., ).

In 1986, Jungck [24] introduced the more generalized commuting mappings in metric spaces, called compatible mappings, which also are more general than the concept of weakly commuting mappings (that is, the mappings are said to be * weakly commuting* if for all ) introduced by Sessa [34] as follows.

*Definition 4. *Let and be mappings from a metric space into itself. The mappings and are said to be *compatible* if
whenever is a sequence in such that for some .

In general, commuting mappings are weakly commuting and weakly commuting mappings are compatible, but the converses are not necessarily true and some examples can be found in [24–26].

In [27], Jungck and Rhoades introduced the concept of weakly compatible mappings and proved some common fixed point theorems for these mappings.

*Definition 5. *The mappings and are said to be *weakly compatible* if they commute at coincidence points of and .

In Djoudi and Nisse [21], we can find an example to show that there exists weakly compatible mappings which are not compatible mappings in metric spaces.

Let denote the set of all functions such that(a)is continuous;(b) is strictly increasing in all the variables;(c)for all , It is easy to verify that the following functions are from the class , see [18]:

*Definition 6 (see [18]). *Let be a partially ordered set and suppose that there exists a metric in such that is a metric space. The mapping is said to be a - *contractive* mapping, if
for .

Recently, Chen introduced -contractive mappings. The purpose of this paper is to extend the results of Chen for four mappings, in the framework of ordered metric spaces.

#### 2. Main Results

Now, we give the main results in this paper.

Theorem 7. * Let be a partially ordered set, and suppose that there exists a metric on such that is a complete metric space. Suppose that , , , and are self-mappings on , the pairs and are partially weakly increasing with and , and the dominating mappings and are weak annihilators of and , respectively. Further, suppose that for any two comparable elements , and ,
**
holds. If, for a nondecreasing sequence with for all , implies that and either*(a)* and are compatible, or is continuous, and are weakly compatible or*(b)* and are compatible, or is continuous, and are weakly compatible,** then , and have a common fixed point in . Moreover, the set of common fixed points of , and is well ordered if and only if , and have one and only one common fixed point in .*

*Proof. * Let be an arbitrary point. Since and , we can construct the sequences and in such that
for each . By assumptions, we have
for each . Thus, for each , we have . Without loss of generality, we assume that for each .

Now, we claim that for all , we have

Suppose to the contrary that ) for some . Since and are comparable, from (5), we have
which is a contradiction. Hence for each .

Similarly, we can prove that for each .

Therefore, we can conclude that (8) holds.

Let us denote . Then, from (8), is a nonincreasing sequence and bounded below. Thus, it must converge to some . If , then by the above inequalities, we have . Taking the limit, as , we have , which is a contradiction. Hence,

Now, we show that is a Cauchy sequence.

Suppose that is not a Cauchy sequence. Then, there exists for which we can find two sequences of natural numbers and with such that
From (11), it follows that
Letting and using (10), we have

Again,
Letting in the above inequalities and using (10) and (13), we have
Again,
Letting in the above inequalities and using (10) and (15), we have
Similarly, we have
Also, again from (10), (15), and the inequality
it follows that
Now, we have
Letting , we get
which is a contradiction. Thus is a Cauchy sequence. Since is a complete metric space, there exists such that . Therefore, we have
Assume that is continuous. Since and are compatible, we have
Also, . Now, we have
Letting , we get
which implies that .

Now, it follows that and , . From (5), we have
Letting , we get
which implies that . Since , there exists such that . Suppose that . Since implies , from (5), we obtain
which implies that . Since and are weakly compatible, . Thus, is a coincidence point of and .

Now, and implies . Thus, from (5), we obtain
Letting , we get
which implies that . Therefore, we have .

If is continuous, then, following the similar arguments, also we get the result.

Similarly, the result follows when (b) holds.

Now, suppose that the set of common fixed points of , , , and is well ordered.

We claim that common fixed points of , , , and are unique.

Assume that and , but . Then, from (5), we have
This implies that , and hence .

Conversely, if , , , and have only one common fixed point, then the set of common fixed point of , , , and being singleton is well ordered. This completes the proof.

*Example 8. * Consider with usual ordering and
Then is a complete partially ordered metric space.

Let , and be self-mappings on defined as
Define function by the formula
Note that , and satisfy all the conditions given in Theorem 7. Moreover, is a common fixed point of , and .

If , then we have the following result.

Corollary 9. *Let be a partially ordered set, and suppose that there exists a metric on such that is a complete metric space. Suppose that , , and are self-mappings on , the pairs and are partially weakly increasing with and , and the dominating mapping is a weak annihilator of and . Further, suppose that there exists the function such that, for any two comparable elements ,
**
holds. If, for a nondecreasing sequence with for all , implies that and either*(a)* are compatible, or is continuous, and are weakly compatible or*(b)* are compatible, or is continuous, and are weakly compatible,** then , and have a common fixed point in . Moreover, the set of common fixed points of , and is well ordered if and only if , and have one and only one common fixed point in . *

Corollary 10. * Let be a partially ordered set, and suppose that there exists a metric on such that is a complete metric space. Suppose that , , and are self-mappings on , the pairs and are partially weakly increasing with and , and the dominating mappings and are weak annihilators of . Further, suppose that there exists the function such that, for any two comparable elements ,
**
holds. If, for a nondecreasing sequence with for all , implies that and either*(a)* are compatible, or is continuous, and are weakly compatible or*(b)* are compatible, or is continuous, and are weakly compatible,** then , and have a common fixed point in . Moreover, the set of common fixed points of , and is well ordered if and only if , and have one and only one common fixed point in .*

Corollary 11. *Let be a partially ordered set, and suppose that there exists a metric on such that is a complete metric space. Suppose that and are self-mappings on , the pair is partially weakly increasing with , and the dominating mapping is a weak annihilator of . Further, suppose that there exists the function such that, for any two comparable elements ,
**
holds. If, for a nondecreasing sequence with for all , implies that and, further, are compatible, or is continuous, and are weakly compatible, then and have a common fixed point in . Moreover, the set of common fixed points of and is well ordered if and only if and have one and only one common fixed point in .*

#### 3. Applications

The aim of the section is to apply our new results to mappings involving contractions of integral type. For this purpose, denote by the set of functions satisfying the following hypotheses:(h1) is a Lebesgue-integrable mapping on each compact of ;(h2)for any , we have .

Corollary 12. * Let be a partially ordered set, and suppose that there exists a metric on such that is a complete metric space. Suppose that , , , and are self-mappings on , the pairs and are partially weakly increasing with and , and the dominating mappings and are weak annihilators of and , respectively. Further, suppose that there exists the function such that, for any two comparable elements ,
**
holds, where . If, for a nondecreasing sequence with for all , implies that and either*(a)* are compatible, or is continuous, and are weakly compatible or*(b)* are compatible, or is continuous, and are weakly compatible,*

Corollary 13. *Let be a partially ordered set, and suppose that there exists a metric on such that is a complete metric space. Suppose that , , and are self-mappings on , the pairs and are partially weakly increasing with and , and the dominating mappings and are weak annihilators of . Further, suppose that there exists the function such that, for any two comparable elements ,
**
holds, where . If, for a nondecreasing sequence with for all , implies that and either*(a)* are compatible, or is continuous, and are weakly compatible or*(b)* are compatible, or is continuous, and are weakly compatible,*

Corollary 14. *Let be a partially ordered set, and suppose that there exists a metric on such that is a complete metric space. Suppose that and are self-mappings on , the pair is a partially weakly increasing with , and the dominating mapping is a weak annihilator of . Further, suppose that there exists the function such that, for any two comparable elements ,
**
holds, where . If, for a nondecreasing sequence with for all , implies that and, further, are compatible, or is continuous, and are weakly compatible, then and have a common fixed point in . Moreover, the set of common fixed points of and is well ordered if and only if and have one and only one common fixed point in .*

#### Conflict of Interests

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

#### References

- M. Abbas, Y. J. Cho, and T. Nazir, “Common fixed point theorems for four mappings in TVS-valued cone metric spaces,”
*Journal of Mathematical Inequalities*, vol. 5, no. 2, pp. 287–299, 2011. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - M. Abbas and M. A. Khan, “Common fixed point theorem of two mappings satisfying a generalized weak contractive condition,”
*International Journal of Mathematics and Mathematical Sciences*, vol. 2009, Article ID 131068, 9 pages, 2009. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - M. Abbas, T. Nazir, and S. Radenović, “Common fixed points of four maps in partially ordered metric spaces,”
*Applied Mathematics Letters*, vol. 24, no. 9, pp. 1520–1526, 2011. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - I. Altun, B. Damjanović, and D. Djorić, “Fixed point and common fixed point theorems on ordered cone metric spaces,”
*Applied Mathematics Letters*, vol. 23, no. 3, pp. 310–316, 2010. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - H. Aydi, M. Postolache, and W. Shatanawi, “Coupled fixed point results for $(\psi ,\varphi )$-metric spaces,”
*Computers & Mathematics with Applications*, vol. 63, no. 1, pp. 298–309, 2012. View at Publisher · View at Google Scholar · View at MathSciNet - H. Aydi, E. Karapinar, and M. Postolache, “Tripled coincidence point theorems for weak $\varphi $-contractions in partially ordered metric spaces,”
*Fixed Point Theory and Applications*, vol. 2012, article 44, 2012. View at Publisher · View at Google Scholar · View at MathSciNet - H. Aydi, W. Shatanawi, M. Postolache, Z. Mustafa, and N. Tahat, “Theorems for Boyd-Wong-type contractions in ordered metric spaces,”
*Abstract and Applied Analysis*, vol. 2012, Article ID 359054, 14 pages, 2012. View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - T. Gnana Bhaskar and V. Lakshmikantham, “Fixed point theorems in partially ordered metric spaces and applications,”
*Nonlinear Analysis. Theory, Methods & Applications*, vol. 65, no. 7, pp. 1379–1393, 2006. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - A. Branciari, “A fixed point theorem for mappings satisfying a general contractive condition of integral type,”
*International Journal of Mathematics and Mathematical Sciences*, vol. 29, no. 9, pp. 531–536, 2002. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - S. Chandok, “Some common fixed point theorems for generalized $f$-weakly contractive mappings,”
*Journal of Applied Mathematics & Informatics*, vol. 29, no. 1-2, pp. 257–265, 2011. View at Google Scholar · View at MathSciNet - S. Chandok, “Some common fixed point theorems for generalized nonlinear contractive mappings,”
*Computers & Mathematics with Applications*, vol. 62, no. 10, pp. 3692–3699, 2011. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - S. Chandok, “Common fixed points, invariant approximation and generalized weak contractions,”
*International Journal of Mathematics and Mathematical Sciences*, vol. 2012, Article ID 102980, 11 pages, 2012. View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - S. Chandok, “Some common fixed point results for generalized weak contractive mappings in partially ordered metric spaces,”
*Journal of Nonlinear Analysis and Optimization*, vol. 4, no. 1, pp. 45–52, 2013. View at Google Scholar - S. Chandok, M. S. Khan, and K. P. R. Rao, “Some coupled common fixed point theorems for a pair of mappings satisfying a contractive condition of rational type without monotonicity,”
*International Journal of Mathematical Analysis*, vol. 7, no. 9-12, pp. 433–440, 2013. View at Google Scholar · View at MathSciNet - S. Chandok, Z. Mustafa, and M. Postolache, “Coupled common fixed point theorems for mixed g-monotone mappings in partially ordered G-metric spaces,”
*UPB Scientific Bulletin A*. In press. - S. Chandok and M. Postolache, “Fixed point theorem for weakly Chatterjea-type cyclic contractions,”
*Fixed Point Theory and Applications*, vol. 2012, article 28, 2013. View at Publisher · View at Google Scholar · View at MathSciNet - S. Chandok, W. Sintunavarat, and P. Kumam, “Some coupled common fixed points for a pair of mappings in partially ordered G-metric spaces,”
*Mathematical Sciences*, vol. 7, article 24, 2013. View at Publisher · View at Google Scholar - C.-M. Chen, “Fixed point theorems for $\psi $-contractive mappings in ordered metric spaces,”
*Journal of Applied Mathematics*, vol. 2012, Article ID 756453, 10 pages, 2012. View at Publisher · View at Google Scholar · View at MathSciNet - B. S. Choudhury, N. Metiya, and M. Postolache, “A generalized weak contraction principle with applications to coupled coincidence point problems,”
*Fixed Point Theory and Applications*, vol. 2013, article 152, 2013. View at Publisher · View at Google Scholar · View at MathSciNet - L. Ćirić, “A generalization of Banach’s contraction principle,”
*Proceedings of the American Mathematical Society*, vol. 45, no. 2, pp. 26–273, 1974. View at Google Scholar - A. Djoudi and L. Nisse, “Greguš type fixed points for weakly compatible maps,”
*Bulletin of the Belgian Mathematical Society*, vol. 10, no. 3, pp. 369–378, 2003. View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - E. Graily, S. M. Vaezpour, R. Saadati, and Y. J. Cho, “Generalization of fixed point theorems in ordered metric spaces concerning generalized distance,”
*Fixed Point Theory and Applications*, vol. 2011, article 30, 2011. View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - R. H. Haghi, M. Postolache, and Sh. Rezapour, “On T-stability of the Picard iteration for generalized $\phi $-contraction mappings,”
*Abstract and Applied Analysis*, vol. 2012, Article ID 658971, 7 pages, 2012. View at Google Scholar · View at MathSciNet - G. Jungck, “Compatible mappings and common fixed points,”
*International Journal of Mathematics and Mathematical Sciences*, vol. 9, no. 4, pp. 771–779, 1986. View at Publisher · View at Google Scholar · View at MathSciNet - G. Jungck, “Compatible mappings and common fixed points. II,”
*International Journal of Mathematics and Mathematical Sciences*, vol. 11, no. 2, pp. 285–288, 1988. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - G. Jungck, “Common fixed points for commuting and compatible maps on compacta,”
*Proceedings of the American Mathematical Society*, vol. 103, no. 3, pp. 977–983, 1988. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - G. Jungck and B. E. Rhoades, “Fixed points for set valued functions without continuity,”
*Indian Journal of Pure and Applied Mathematics*, vol. 29, no. 3, pp. 227–238, 1998. View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - G. Jungck and B. E. Rhoades, “Fixed point theorems for occasionally weakly compatible mappings,”
*Fixed Point Theory*, vol. 7, no. 2, pp. 287–296, 2006. View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - J. J. Nieto and R. Rodríguez-López, “Contractive mapping theorems in partially ordered sets and applications to ordinary differential equations,”
*Order*, vol. 22, no. 3, pp. 223–239, 2005. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - J. J. Nieto and R. Rodríguez-López, “Existence and uniqueness of fixed point in partially ordered sets and applications to ordinary differential equations,”
*Acta Mathematica Sinica*, vol. 23, no. 12, pp. 2205–2212, 2007. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - M. O. Olatinwo and M. Postolache, “Stability results of Jungck-type iterative processes in convex metric spaces,”
*Applied Mathematics and Computation*, vol. 218, no. 12, pp. 6727–6732, 2012. View at Publisher · View at Google Scholar · View at MathSciNet - A. C. M. Ran and M. C. B. Reurings, “A fixed point theorem in partially ordered sets and some applications to matrix equations,”
*Proceedings of the American Mathematical Society*, vol. 132, no. 5, pp. 1435–1443, 2004. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - B. Samet and H. Yazidi, “Fixed point theorems with respect to a contractive condition of integral type,”
*Rendiconti del Circolo Matematico di Palermo*, vol. 60, no. 1-2, pp. 181–190, 2011. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - S. Sessa, “On a weak commutativity condition of mappings in fixed point considerations,”
*Publications de l'Institut Mathématique*, vol. 32, no. 46, pp. 149–153, 1982. View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - W. Shatanawi and M. Postolache, “Some fixed-point results for a $G$-weak contraction in $G$-metric spaces,”
*Abstract and Applied Analysis*, vol. 2012, Article ID 815870, 19 pages, 2012. View at Google Scholar · View at MathSciNet - W. Shatanawi and M. Postolache, “Common fixed point theorems for dominating and weak annihilator mappings in ordered metric spaces,”
*Fixed Point Theory and Applications*. In press. - W. Shatanawi and M. Postolache, “Common fixed point results of mappings for nonlinear contractions of cyclic form in ordered metric spaces,”
*Fixed Point Theory and Applications*, vol. 2013, article 60, 2013. View at Google Scholar - W. Shatanawi and M. Postolache, “Coincidence and fixed point results for generalized weak contractions in the sense of Berinde on partial metric spaces,”
*Fixed Point Theory and Applications*, vol. 2013, article 54, 2013. View at Publisher · View at Google Scholar · View at MathSciNet - W. Shatanawi and A. Pitea, “Omega-distance and coupled fixed point in G-metric spaces,”
*Fixed Point Theory and Applications*, vol. 2013, article 208, 2013. View at Google Scholar - W. Shatanawi and A. Pitea, “Some coupled fixed point theorems in quasi-partial metric spaces,”
*Fixed Point Theory and Applications*, vol. 2013, article 153, 2013. View at Publisher · View at Google Scholar · View at MathSciNet - W. Shatanawi, S. Chauhan, M. Postolache, M. Abbas, and S. Radenović, “Common fixed points for contractive mappings of integral type in G-metric spaces,”
*Journal of Advanced Mathematical Studies*, vol. 6, no. 1, pp. 53–72, 2013. View at Google Scholar