Research Article | Open Access

Meiqiang Feng, Xuemei Zhang, Weigao Ge, "Positive Fixed Point of Strict Set Contraction Operators on Ordered Banach Spaces and Applications", *Abstract and Applied Analysis*, vol. 2010, Article ID 439137, 13 pages, 2010. https://doi.org/10.1155/2010/439137

# Positive Fixed Point of Strict Set Contraction Operators on Ordered Banach Spaces and Applications

**Academic Editor:**Ferhan M. Atici

#### Abstract

The fixed point theorem of cone expansion and compression of norm type for a strict set contraction operator is generalized by replacing the norms with a convex functional satisfying certain conditions. We then show how to apply our theorem to prove the existence of a positive solution to a second-order differential equation with integral boundary conditions in an ordered Banach space. An example is worked out to demonstrate the main results.

#### 1. Introduction

The theory of integral and differential equations in Banach spaces, as two new branches of nonlinear functional analysis, has developed for no more than forty years, but it has extensive applications in such domains as the critical point theory, the theory of partial differential equations, and eigenvalue problems. For an introduction of the basic theory of integral and differential equations in Banach spaces, see Guo et al. [1], Guo and Lakshmikantham [2], Lakshmikantham and Leela [3], and Demling [4], and the references therein. In recent years, the theory of integral and differential equations in Banach spaces has become an important area of investigation in both pure and applied mathematics (see, for instance, [5–18] and references cited therein).

On the other hand, the theory of fixed point is an important tool to study various boundary value problems of ordinary differential equations, difference differential equations, and dynamic equations on time scales. An overview of such results can be found in Guo et al. [1], in Guo and Lakshmikantham [2], and in Demling [4]. The Krasnoselskii's fixed point theorem concerning cone compression and expansion of norm type is worth mentioing here as follows (see [1, 2, 4]).

Theorem 1.1. *Let and be two bounded open sets in Banach space , such that and . Let be a cone in and let operator be completely continuous. Suppose that one of the following two conditions is satisfied: *(a)* and ; *(b)* and .**Then, has at least one fixed point in . *

To generalize Theorem 1.1, one may consider the weakening of one or more of the following hypotheses: (i) the operator , (ii) the norm.

In [19], Sun generalized Theorem 1.1 for completely continuous operator to strict set contraction operator and obtain the following results.

Theorem 1.2. *Let be a cone of Banach space and with Suppose that is a strict set contraction such that one of the following two conditions is satisfied: *(a)(b)*Then, has a fixed point . *

Recently, in [20], Anderson and Avery generalized the fixed point theorem of cone expansion and compression of norm type by replacing the norms with two functionals satisfying certain conditions to produce a fixed point theorem of cone expansion and compression of functional type. In [21], Guo and Ge extended Krasnoselskii's fixed point theorem by choosing two functionals that satisfy certain conditions which are used in place of the norm. In [22], Zhang and Sun generalized the classical Krasnoselskii's fixed point theorem concerning cone compression and expansion of norm type. The interesting point is that they took place norm by convex functional.

In the past few years, we also notice a class of boundary value problems with integral boundary conditions appeared in heat conduction, chemical engineering, underground water flow, thermo elasticity, and plasma physics. Such problems include two, three, multi point and nonlocal boundary value problems as special cases and attracted the attention of Gallardo [23], Karakostas and Tsamatos [24], Lomtatidze and Malaguti [25], and others included in the references therein. On the other hand, we refer the reader to papers by Ahmad et al. [26], Feng et al. [27], Boucherif [28], Infante and Webb [29], Kang et al. [30], Ma [31], Webb [32], Webb and Infante [33, 34], Yang [35], Zhang et al. [36–38], and Chang et al. [39] for other recent results on nonlinear boundary value problems with integral boundary conditions.

Motivated by works mentioned above, we intend in this paper to generalize the fixed point theorem of cone expansion and compression of norm type for strict set contraction operator. The generalization allows the user to choose a convex functional that satisfies certain conditions which are used in place of the norm. In applications to boundary value problems, the functional will typically be maximum of the function over a specific interval. The flexibility of using functionals instead of norms allows the theorem to be used in a wider variety of situations. Our results either improve or generalize the corresponding results due to [19–22] and many of others. As an application of our main results, we consider the existence of positive solutions for second-order differential equations with integral boundary conditions in an ordered Banach space. On the other hand, our conditions are weaker than those of [22].

The organization of this paper is as follows. We will introduce some lemmas and notations in the rest of this section. In Section 2, the main results will be stated and proved. In Section 3, as an application of our main results, the existence of positive solutions for a second-order boundary value problem with integral boundary conditions in ordered Banach spaces is considered. Finally, in Section 4, one example is also included to illustrate the main results.

Basic facts about ordered Banach space can be found in [1–4]. Here we just recall a few of them. The cone in induces a partial order on , that is, if and only if . is said to be normal if there exists a positive constant such that implies . Without loss of generality, suppose, in the present paper, the normal constant .

For a bounded set in Banach space , we denote the Kuratowski measure of noncompactness (see [1–4], for further understanding). The operator is said to be a -set contraction if is continuous and bounded and there is a constant such that for any bounded ; a -set contraction with is called a strict set contraction.

In the following, denote the Kuratowski's measure of noncompactness by .

For the application in the sequel, we first state the following definition and lemmas which can be found in [1], and some notation.

*Definition 1.3. *Let be a bounded set of a real Banach space . Let be expressed as the union of a finite number of sets such that the diameter of each set does not exceed , that is, with . Clearly, . is called the Kuratowski's measure of noncompactness.

*Definition 1.4. *Let be a cone of a real Banach space . If then is a dual cone of cone .

*Definition 1.5. *Let be a cone of real Banach space . is said to be a convex functional on if for all and .

*Definition 1.6. *A subset is said to be a retract of if there exists a continuous mapping satisfying

Lemma 1.7. *Let , be a bounded set and uniformly continuous and bounded from into ; then
*

#### 2. Main Results

Lemma 2.1 (see [22]). *Let be a cone in a real Banach space . If is a uniformly continuous convex functional with and for , then , is a retract of .*

Lemma 2.2. *Let be a real Banach space, the norm in , a cone in , and , where is a positive real number. Suppose that is a -set contraction with and is a uniformly continuous convex functional with , , and . If *(i)* and there exists such that and *(ii)*, **hold, then the fixed point index . *

*Proof. *Without loss of generality, we suppose (If , then let . The proof is the same as the following process). Let , then is a strict set contraction. Considering , , . If there exists , such that then which contradicts with (ii). Then by the homotopy invariance property of fixed point index, we have

Let Define . It follows from that From the fact that , we have . In fact, since we have . On the other hand, for combining this with , we have then Let , then by (i) we obtain and , and , where

Let Then, we have
and then we obtain that is the strict set contraction. In addition, it is obvious that is uniformly continuous about for all

If there exists such that then which contradicts with (ii). Thus by the homotopy invariance property of fixed point index, we have

Since is a retract of by Lemma 2.1, there exists a retraction satisfying Let then is strict set contraction. From (i) and the definition of , we have
Therefore, , that is, , . Then

If then , which implies that has a fixed point in . Thus It is a paradox. The proof is complete.

Lemma 2.3 (see [2]). *Let be a cone and a bounded open set in with . Suppose that is condensing and
**
Then . *

Lemma 2.4. *Let be a cone and a bounded open set in . Suppose that is a -set contraction with and is a uniformly continuous convex functional with and for . If and for then . *

*Proof. *If there exist and such that then Therefore,
It is a paradox. From Lemma 2.3, it follows that . The proof is complete.

Theorem 2.5. *Let be a bounded open set in such that , and and Suppose that is a -set contraction with and is a uniformly continuous convex functional with and and . If *(a)*, *(b)* and there exists such that and and , **hold, then has at least one fixed point in *

*Proof. *It is easy to obtain the results by Lemmas 2.2 and 2.4. So we omit it.

Theorem 2.6. *Let and a bounded open set in such that Suppose that is a -set contraction with and is a uniformly continuous convex functional with and and . If *(a)* and there exists such that and and *(b)*are satisfied, then has at least one fixed point in *

*Proof. *It is easy to obtain the results by Lemmas 2.2 and 2.4. So we omit it.

*Remark 2.7. *If we let , then is completely continuous. Comparing with Corollary of [22], our conditions are weaker.

Corollary 2.8. *Let be a bounded open set in such that , and Suppose that is a -set contraction with and is a uniformly continuous convex functional with and and . If *(a)*, *(b)* with and **hold, then has at least one fixed point in *

*Proof. *It follows by taking .

Corollary 2.9. *Let and a bounded open set in such that Suppose that is a -set contraction with and is a uniformly continuous convex functional with and and . If *(a)* with and *(b)*, **hold, then has at least one fixed point in *

*Proof. *It follows by taking .

#### 3. Applications

Throughout the remainder of this paper, we apply the above results to a second-order differential equation in Banach spaces: subject to the following integral boundary conditions: where , is the zero element of , and is nonnegative.

We consider problem (3.1)-(3.2) in , in which . Evidently, is a Banach space with norm for .

To establish the existence of positive solutions in of (3.1)-(3.2), let us list the following assumptions.

?? and for any is uniformly continuous on . Further suppose that is nonnegative, and there exist nonnegative constants with such that where , , and .

It is easy to see that the problem (3.1)-(3.2) has a solution if and only if is a solution of the operator equation where

From (3.6) and (3.7), we can prove that have the following properties.

Proposition 3.1. *Assume that holds. Then for we have
*

Proposition 3.2. *For , we have
*

Proposition 3.3. *Let , . Then for all , we have
*

Proposition 3.4. *Assume that holds. Then for , we have
**
where is defined in , and
*

*Proof. *By (3.6) and (3.9), we have

On the other hand, noticing , we obtain

Proposition 3.5. *Assume that holds. Then for all we have
*

*Proof. *By (3.10), we have

We construct a cone by where

It is easy to see that is a cone of .

We will make use of the following lemmas.

Lemma 3.6. *Suppose that holds. Then for each is strict set contraction on , that is, there exists a constant such that for any , where . *

*Proof. *By , we know that is uniformly continuous on . Hence, is bounded on . This together with (3.4) and Lemma 1.7 implies that
From being uniformly continuous and bounded on , we can obtain that is continuous and bounded from into .

On the other hand, it is clear that and using a similar method as in the proof of Lemma in [40], we can get that

Therefore,
where , The proof is complete.

Lemma 3.7. *Suppose that holds. Then and is a strict set contraction. *

*Proof. *From (3.5) and (3.15), we obtain
Therefore, , that is, .

Next by Lemma 3.6, one can prove that is a strict set contraction. So it is omitted.

Let

Theorem 3.8. *Assume that holds and is normal. If there exist with such that for and for where then problem (3.1)-(3.2) has at least one positive solution. *

*Proof. *Let be the cone preserving, strict set contraction that was defined by (3.5).

Let . Then is a uniformly continuous convex functional with and for Let

It is clear that and are open sets in with and If we have which implies that is bounded.

If then .

If then and .

Hence, the proof is finished by Corollary 2.9.

#### 4. Example

*Example 4.1. *To illustrate how our main results can be used in practice, we present an example. For the convenience of computation, we study a two-point boundary value problem. Now we consider the following boundary value problem:
where and
Hence , In this case , and . Let ,?? then

Select then we can see that
Hence, the conditions of the Theorem 3.8 are satisfied. Then problem (4.1) has at least one positive solution.

*Remark 4.2. *Example 4.1 implies that there is a large number of functions that satisfy the conditions of Theorem 3.8. In addition, the conditions of Theorem 3.8 are also easy to check.

#### Acknowledgments

This work is sponsored by the Funding Project for Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipality (PHR201008430), the Scientific Research Common Program of Beijing Municipal Commission of Education (KM201010772018), the 2010 level of scientific research of improving project (5028123900), the Level of Graduate Education of Improving-Graduate Technology Innovation Project (5028211000), and Beijing Municipal Education Commission (71D0911003). The authors thank the referee for his/her careful reading of the manuscript and useful suggestions.

#### References

- D. Guo, V. Lakshmikantham, and X. Liu,
*Nonlinear Integral Equations in Abstract Spaces*, vol. 373 of*Mathematics and Its Applications*, Kluwer Academic Publishers, Dordrecht, The Netherlands, 1996. View at: Zentralblatt MATH | MathSciNet - D. Guo and V. Lakshmikantham,
*Nonlinear Problems in Abstract Cones*, vol. 5 of*Notes and Reports in Mathematics in Science and Engineering*, Academic Press, Boston, Mass, USA, 1988. View at: Zentralblatt MATH | MathSciNet - V. Lakshmikanthan and S. Leela,
*Nonlinear Differential Equations in Abstract Spaces*, Pergamon, Oxford, UK, 1981. - K. Demling,
*Ordinary Differential Equations in Banach Spaces*, Springer, Berlin, Germany, 1977. - M. Feng and H. Pang, “A class of three-point boundary-value problems for second-order impulsive integro-differential equations in Banach spaces,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 70, no. 1, pp. 64–82, 2009. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - M. Feng, D. Ji, and W. Ge, “Positive solutions for a class of boundary-value problem with integral boundary conditions in Banach spaces,”
*Journal of Computational and Applied Mathematics*, vol. 222, no. 2, pp. 351–363, 2008. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - D. Guo, “Multiple positive solutions for first order nonlinear impulsive integro-differential equations in a Banach space,”
*Applied Mathematics and Computation*, vol. 143, no. 2-3, pp. 233–249, 2003. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - D. Guo, “Multiple positive solutions of a boundary value problem for $n$th-order impulsive integro-differential equations in a Banach space,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 56, no. 7, pp. 985–1006, 2004. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - D. Guo, “Multiple positive solutions for $n$th-order impulsive integro-differential equations in Banach spaces,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 60, no. 5, pp. 955–976, 2005. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - Y. Cui and Y. Zou, “Positive solutions of nonlinear singular boundary value problems in abstract spaces,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 69, no. 1, pp. 287–294, 2008. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - X. Zhang and L. Liu, “Initial value problems for nonlinear second order impulsive integro-differential equations of mixed type in Banach spaces,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 64, no. 11, pp. 2562–2574, 2006. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - L. Liu, Z. Liu, and Y. Wu, “Infinite boundary value problems for $n$th-order nonlinear impulsive integro-differential equations in Banach spaces,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 67, no. 9, pp. 2670–2679, 2007. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - Y. Liu, “Boundary value problems for second order differential equations on unbounded domains in a Banach space,”
*Applied Mathematics and Computation*, vol. 135, no. 2-3, pp. 569–583, 2003. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - Y. Liu and A. Qi, “Positive solutions of nonlinear singular boundary value problem in abstract space,”
*Computers & Mathematics with Applications*, vol. 47, no. 4-5, pp. 683–688, 2004. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - B. Liu, “Positive solutions of a nonlinear four-point boundary value problems in Banach spaces,”
*Journal of Mathematical Analysis and Applications*, vol. 305, no. 1, pp. 253–276, 2005. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - X. Zhang, M. Feng, and W. Ge, “Existence and nonexistence of positive solutions for a class of $n$th-order three-point boundary value problems in Banach spaces,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 70, no. 2, pp. 584–597, 2009. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - X. Zhang, “Existence of positive solutions for multi-point boundary value problems on infinite intervals in Banach spaces,”
*Applied Mathematics and Computation*, vol. 206, no. 2, pp. 932–941, 2008. View at: Google Scholar | Zentralblatt MATH | MathSciNet - X. Zhang, “Existence of positive solution for second-order nonlinear impulsive singular differential equations of mixed type in Banach spaces,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 70, no. 4, pp. 1620–1628, 2009. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - J. X. Sun, “A generalization of Guo's theorem and applications,”
*Journal of Mathematical Analysis and Applications*, vol. 126, no. 2, pp. 566–573, 1987. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - D. R. Anderson and R. I. Avery, “Fixed point theorem of cone expansion and compression of functional type,”
*Journal of Difference Equations and Applications*, vol. 8, no. 11, pp. 1073–1083, 2002. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - Y. Guo and W. Ge, “Positive solutions for three-point boundary value problems with dependence on the first order derivative,”
*Journal of Mathematical Analysis and Applications*, vol. 290, no. 1, pp. 291–301, 2004. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - G. Zhang and J. Sun, “A generalization of the cone expansion and compression fixed point theorem and applications,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 67, no. 2, pp. 579–586, 2007. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - J. M. Gallardo, “Second-order differential operators with integral boundary conditions and generation of analytic semigroups,”
*The Rocky Mountain Journal of Mathematics*, vol. 30, no. 4, pp. 1265–1292, 2000. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - G. L. Karakostas and P. Ch. Tsamatos, “Multiple positive solutions of some Fredholm integral equations arisen from nonlocal boundary-value problems,”
*Electronic Journal of Differential Equations*, vol. 2002, no. 30, pp. 1–17, 2002. View at: Google Scholar | Zentralblatt MATH | MathSciNet - A. Lomtatidze and L. Malaguti, “On a nonlocal boundary value problem for second order nonlinear singular differential equations,”
*Georgian Mathematical Journal*, vol. 7, no. 1, pp. 133–154, 2000. View at: Google Scholar | Zentralblatt MATH | MathSciNet - B. Ahmad, A. Alsaedi, and B. S. Alghamdi, “Analytic approximation of solutions of the forced Duffing equation with integral boundary conditions,”
*Nonlinear Analysis: Real World Applications*, vol. 9, no. 4, pp. 1727–1740, 2008. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - M. Feng, B. Du, and W. Ge, “Impulsive boundary value problems with integral boundary conditions and one-dimensional $p$-Laplacian,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 70, no. 9, pp. 3119–3126, 2009. View at: Publisher Site | Google Scholar | MathSciNet - A. Boucherif, “Second-order boundary value problems with integral boundary conditions,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 70, no. 1, pp. 364–371, 2009. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - G. Infante and J. R. L. Webb, “Nonlinear non-local boundary-value problems and perturbed Hammerstein integral equations,”
*Proceedings of the Edinburgh Mathematical Society*, vol. 49, no. 3, pp. 637–656, 2006. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - P. Kang, Z. Wei, and J. Xu, “Positive solutions to fourth-order singular boundary value problems with integral boundary conditions in abstract spaces,”
*Applied Mathematics and Computation*, vol. 206, no. 1, pp. 245–256, 2008. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - H. Ma, “Symmetric positive solutions for nonlocal boundary value problems of fourth order,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 68, no. 3, pp. 645–651, 2008. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - J. R. L. Webb, “Positive solutions of some three point boundary value problems via fixed point index theory,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 47, no. 7, pp. 4319–4332, 2001. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - J. R. L. Webb and G. Infante, “Positive solutions of nonlocal boundary value problems: a unified approach,”
*Journal of the London Mathematical Society*, vol. 74, no. 3, pp. 673–693, 2006. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - J. R. L. Webb, G. Infante, and D. Franco, “Positive solutions of nonlinear fourth-order boundary-value problems with local and non-local boundary conditions,”
*Proceedings of the Royal Society of Edinburgh. Section A*, vol. 138, no. 2, pp. 427–446, 2008. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - Z. Yang, “Positive solutions to a system of second-order nonlocal boundary value problems,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 62, no. 7, pp. 1251–1265, 2005. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - X. Zhang, M. Feng, and W. Ge, “Existence results for nonlinear boundary-value problems with integral boundary conditions in Banach spaces,”
*Nonlinear Analysis: Theory, Methods & Applications*, vol. 69, no. 10, pp. 3310–3321, 2008. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - X. Zhang, M. Feng, and W. Ge, “Symmetric positive solutions for $p$-Laplacian fourth-order differential equations with integral boundary conditions,”
*Journal of Computational and Applied Mathematics*, vol. 222, no. 2, pp. 561–573, 2008. View at: Publisher Site | Google Scholar | MathSciNet - X. Zhang, M. Feng, and W. Ge, “Existence result of second-order differential equations with integral boundary conditions at resonance,”
*Journal of Mathematical Analysis and Applications*, vol. 353, no. 1, pp. 311–319, 2009. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet - Y.-K. Chang, J. J. Nieto, and W.-S. Li, “On impulsive hyperbolic differential inclusions with nonlocal initial conditions,”
*Journal of Optimization Theory and Applications*, vol. 140, no. 3, pp. 431–442, 2009. View at: Publisher Site | Google Scholar | Zentralblatt MATH - D. Guo and V. Lakshmikantham, “Multiple solutions of two-point boundary value problems of ordinary differential equations in Banach spaces,”
*Journal of Mathematical Analysis and Applications*, vol. 129, no. 1, pp. 211–222, 1988. View at: Publisher Site | Google Scholar | Zentralblatt MATH | MathSciNet

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Copyright © 2010 Meiqiang Feng et al. 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.