`ISRN Applied MathematicsVolumeΒ 2011, Article IDΒ 612591, 13 pageshttp://dx.doi.org/10.5402/2011/612591`
Research Article

## Positive Solutions for Second-Order Nonlinear Ordinary Differential Systems with Two Parameters

Lan Sun,1Β Yukun An,1Β and Min Jiang2

1Department of Mathematics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
2College of Computer Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Received 7 September 2011; Accepted 23 October 2011

Copyright Β© 2011 Lan Sun 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.

#### Abstract

By using fixed-point theorem and under suitable conditions, we investigate the existence and multiplicity positive solutions to the following systems: , where are four positive constants and , , and . We derive two explicit intervals of and , such that the existence and multiplicity of positive solutions for the systems is guaranteed.

#### 1. Introduction

In this paper, we are concerned with the existence and multiplicity of positive solutions to the following boundary value problem of second-order nonlinear differential systems with two parameters: where are four positive constants.

In addition, we assume the following conditions throughout this paper:() does not vanish identically on any subinterval of ;(); ().

The boundary value problem of ordinary differential systems has attracted much attention, see [1β6] and the references therein. Recently, Fink and Gatica [4] and Ma [7] have studied the existence of positive solutions of the following systems: In [4], a multiplicity result has been established when . In [7], a multiplicity result has been given for the more general case .

Also, by using Krasnoselskill fixed-point theorem, Ru and An [8] considered the existence of positive solutions of the following systems: where , .

More recently, Dalbono and Mckenna [5] proved the existence and multiplicity of solutions to a class of asymmetric weakly coupled systems as follows: where is suitably small and the positive numbers , satisfy Applying a classical change of variables, the authors transformed the initial problem into an equivalent problem whose solutions can be characterized by their nodal properties. Meanwhile, in [5], there are two open questions. (1)Can one replace the near-diagonal matrix with something more general and use information on the eigenvalues of matrix?(2)Can one replace the near-diagonal matrix with something more general and use information on the eigenvalues of matrix?

Inspired by the above works and the two open questions, we consider the existence and multiplicity of positive solutions to (1.1). The paper is organized as follows. In Section 2, we state some preliminaries. In Sections 3 and 4, we prove the existence and multiplicity results of (1.1).

#### 2. Preliminaries

In order to prove our results, we state the well-known fixed-point theorem [9]:

Lemma 2.1. Let be a Banach space and let be a cone in . Assume , are two open subsets of with , , and let be a completely continuous operator such that either(i) and ; or(ii) and .Then, has a fixed point in .
To be convenient, we introduce the following notations: and suppose that .
Let , be function of the corresponding to linear boundary value problem: Then, the solution of (2.2) is given by It is well known that can be expressed by In addition, it can be easily to be checked that

See [6], we have the following lemma.

Lemma 2.2. has the following properties:(i), (ii), (iii). It is obvious that problem (1.1) is equivalent to the equation: and consequently it is equivalent to the fixed-point problem: with given by For convenience, denote It is obvious that is completely continuous. Let , and define a cone in by where .

Lemma 2.3. . Proof. For any , by Lemma 2.2, we have Similarly, for any , we have Then, for any , we have Thus, . Therefore, .

#### 3. Existence Results

We assume the following:; ; .

Theorem 3.1. Assume β hold. Then one has the following:
(1)If , then for each and , (1.1) has at least one positive solution. (2)If , then for each and , (1.1) has at least one positive solution. (3)If , then for each and , (1.1) has at least one positive solution.(4)If , then for each and , (1.1) has at least one positive solution.(5)If and , then for each and , (1.1) has at least one positive solution.(6)If or , then for each and , (1.1) has at least one positive solution. (7)If and , then for each or (1.1) has at least one positive solution.

Proof. We only prove case (1.1). The other cases can be proved similarly. In order to apply the Lemma 2.1, we construct the sets .
Let , and we choose such that
By the definition of and , there exists , such that Choosing with , we have namely, . In the same way, we also have then . Thus, if we set , then On the other hand, by the definition of , there exists , such that , for . Let and . If we choose with , such that , then we have Hence Therefore, it follows from (3.5) to (3.7) and Lemma 2.2, has a fixed point , which is a positive solution of (1.1).

Similarly, we also have the following results.

Theorem 3.2. Assume β hold. Then one has the following:(1)If , then for each and , (1.1) has at least one positive solution.(2)If , then for each and , (1.1) has at least one positive solution.(3)If , then for each and , (1.1) has at least one positive solution.(4)If , then for each and , (1.1) has at least one positive solution.(5)If and , then for each and , (1.1) has at least one positive solution.(6)If or then for each and , (1.1) has at least one positive solution.(7)If and then for each or , (1.1) has at least one positive solution.

Proof. We only prove case . The other cases can be proved similarly.
Let , and we choose such that
by the definition of , there exists , such that Choosing with , such that , then we have So, if we set , then On the other hand, by the definition of and , there exists , such that Choosing with , we have In the same way, we also have Hence, if we set , then Therefore, it follows from (3.11) to (3.15) and Lemma 2.2 that has a fixed point , which is a positive solution of (1.1).

#### 4. Multiplicity Results

Theorem 4.1. Assume β hold. In addition, assume that there exist three constants , where is sufficient small with such that(i), (ii), βfor .Then, for any , , or , , the problem (1.1) has at least two positive solutions.

Proof. We only prove the case of , , The other case is similar.
Step 1. Since , there exists such that Set , then we have In the same way, we also have Hence,
Step 2. Since , there exists such that Similarly, set , then
Step 3. Let , we can see that Then,
Consequently, by Lemma 2.1 and from (4.4)β(4.8), has two fixed points: and , so (1.1) has at least two positive solutions satisfying .

Theorem 4.2. Assume β hold. In addition, assume that there exist constants , where is sufficient large with such that(i) or ,(ii) or , βfor ,then, for any , , or , , the problem (1.1) has at least two positive solutions.

Proof. We only prove the case of , , The other case is similar.
Step 1. Since , there exists such that Set , then we have Hence,
Step 2. Since , there exists such that Similarly, set , then
Step 3. Let , we can see that In the same way, we also have Hence,

Consequently, by Lemma 2.1 and from (4.11)β(4.16), has two fixed points: and , so (1.1) has at least two positive solutions satisfying .

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