Abstract
This paper is concerned with the existence, multiplicity, and nonexistence of positive solutions for nonhomogeneous mpoint boundary value problems with two parameters. The proof is based on the fixedpoint theorem, the upperlower solutions method, and the fixedpoint index.
MSC: 34B10, 34B18.
Keywords:
nonhomogeneous BVP; positive solutions; upperlower solutions; fixedpoint theorem; fixed point index1 Introduction
Many authors have studied the existence, nonexistence, and multiplicity of positive solutions for multipoint boundary value problems by using the fixedpoint theorem, the fixed point index theory, and the lower and upper solutions method. We refer the readers to the references [14]. Recently, Hao, Liu and Wu [5] studied the existence, nonexistence, and multiplicity of positive solutions for the following nonhomogeneous boundary value problems:
where , (), , , may be singular at and/or . They showed that there exists a positive number such that the problem has at least two positive solutions for , at least one positive solution for and no solution for by using the Krasnosel’skiiGuo fixedpoint theorem, the upperlower solutions method, and the topological degree theory.
Inspired by the above references, the purpose of this paper is to study the following more general nonhomogeneous boundary value problems:
where λ, μ are positive parameters, , . The main result of the present paper is summarized as follows.
Theorem 1.1Assume the following conditions hold:
(H1) are nonnegative parameters;
(H2) is continuous, does not vanish identically on any subinterval ofand, whereis given in Sect. 2;
(H3) is nondecreasing with respect tou, respectively, that is,
(H4) There exist constantssuch thatand, respectively, for all;
If, then there exists a bounded and continuous curve Γ separatinginto two disjoint subsetsandsuch that (1) has at least two positive solutions for, one positive solution for, and no solution for. Moreover, letbe the parametric representation of Γ, where
Then on, the functionis continuous and nonincreasing, that is, if, we have.
For the proof of Theorem 1.1, we also need the following lemmas.
Lemma 1.2[6]
LetEbe a Banach space, Ka cone inEand Ω bounded open inE. Letandbe condensing. Suppose thatfor alland all. Then
Lemma 1.3[6]
LetEbe a Banach space andKa cone inE. For, define. Assume thatis a compact map such thatfor. Iffor all, then
2 Preliminaries
Lemma 2.1[5]
Assume that. Ifwith, then the Green function for the homogeneous BVP
is given by
Moreover, the Green function satisfies the following properties:
Lemma 2.2Assume that (H1)(H5) hold. If, thenis a solution of (1) if and only ifsatisfies the following nonlinear integral equation:
Proof Integrating both sides of (1) from 0 to t twice and applying the boundary conditions, then we can obtain
Furthermore, by Lemma 2.1, we can obtain
□
Let E denote the Banach space with the norm . A function is said to be a solution of (1) if satisfies (1). Moreover, from Lemma 2.2, it is clear to see that is a solution of (1) is equivalent to the fixed point of the operator T defined as
Lemma 2.3If (H1)(H3) hold, thenis completely continuous.
The proof procedure of Lemma 2.3 is standard, so we omit it.
Now, we will establish the classical lower and upper solutions method for our problem. As usual, we say that is a lower solution for (1) if
Similarly, we define the upper solution of the problem (1):
Lemma 2.4Let, be lower and upper solutions, respectively, of (1) such that. Then (1) has a nonnegative solutionsatisfyingfor.
Proof Define
It is clear to see that is a bounded, convex and closed subset in Banach space E. Now we can prove that .
On the other hand, we also have
From above inequalities, we obtain that .
Therefore, by Schauder’s fixed theorem, the operator T has a fixed point , which is the solution of (1). □
3 Proof of Theorem 1.1
Lemma 3.1Assume (H1)(H5) hold and Σ be a compact subset of. Then there exists a constantsuch that for alland all possible positive solutionsof (1) at, one has.
Proof Suppose on the contrary that there exists a sequence of positive solutions of Eq. (1) at such that for all and
Since Σ is compact, the sequence has a convergent subsequence which we denote without loss of generality still by such that
Case (I). If , we have for n sufficient large. Then by (H5), there exists a such that
where L satisfies
Since , for n sufficient large, we
This is a contradiction.
Case (II). If , then we have for n sufficient large. Since , there exists a such that
where M satisfies
Since , then for n sufficient large, we have
This is a contradiction. □
Lemma 3.2Assume (H1)(H4) hold. If (1) has a positive solution at, then Eq. (1) has a positive solution atfor all.
Proof Let be the solution of Eq. (1) at , then be the upper solution of (1) at with . Since or , is not a solution of (1), but it is the lower solution of (1) at . Therefore, by Lemma 2.4, we obtain the result. □
Lemma 3.3Assume (H1)(H5) hold. Then there existssuch that Eq. (1) has a positive solution for all.
Proof Let be the unique solution of
It is clear to see that is a positive solution of (3). Let , , then by (H4), we know that and . Set , we have
which implies that is an upper solution of (3) at . On the other hand, 0 is a lower solution of (1) and . By (H3), 0 is not a solution of (1). Hence, (1) has a positive solution at , Lemma 3.2 now implies the conclusion of Lemma 3.3. □
Define a set S by
Then it follows from Lemma 3.3 that and is a partially ordered set.
Lemma 3.4Assume (H1)(H5) hold. Thenis bounded above.
Proof Let and be a positive solution of (1) at , then we have
by (H4). Furthermore, we can obtain that
□
Lemma 3.5Assume (H1)(H5) hold. Then every chain inShas a unique supremum inS.
Lemma 3.6Assume (H1)(H5) hold. Then there exists asuch (1) has a positive solution atfor all, no solution atfor all. Similarly, there exists asuch that (1) has a positive solution atfor all, and no solution atfor all.
Lemma 3.7Assume (H1)(H5) hold. Then there exists a continuous curve Γ separatinginto two disjoint subsetsandsuch thatis bounded andis unbounded, Eq. (1) has at least one solution for, and no solution for. The functionis nonincreasing, that is, if
then
Lemma 3.8Let. Then there existssuch thatis an upper solution of (1) atfor all, whereis the positive solution of Eq. (1) corresponding to somesatisfying
Proof From (H4), there exists constant such that
Then by the uniform continuity of f and g on a compact set, there exist such that
and
From above inequalities, it is clear to see that , is an upper solution of (1) at for all . □
Proof of Theorem 1.1 From above lemmas, we need only to show the existence of the second positive solution of (1) for . Let , then there exists such that
Let be the positive solution of (1) at . Then for given by Lemma 3.8 and for all , denote
Define the set
Then D is bounded open set in E and . The map T satisfies and is condensing, since it is completely continuous. Now let , then there exists such that either . Then by (H) and Lemma 3.8, we obtain
for all . Thus, for all and , Lemma 1.2 now implies that
Now for some fixed λ and μ, it follows from assumption (H4) that there exists a such that
where L satisfies
Let where is given by Lemma 3.1 with Σ a compact set in containing . Let
Then it follows from Lemma 3.1,
Furthermore, we have
Thus, and it follows from Lemma 1.3 that
By the additivity of the fixedpoint index,
which yields
Hence, T has at least one fixed point in and another one in ; this shows that in , (1) has at least two positive solution. □
Example Consider the following boundary value problem:
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
In this paper, the author studies the existence, multiplicity, and nonexistence of positive solutions for nonhomogeneous mpoint boundary value problems with two parameters. The proof is based on the upperlower solutions method and fixedpoint index. All authors typed, read, and approved the final manuscript.
Acknowledgements
The authors would like to thank the referees for valuable comments and suggestions for improving this paper. The first author is supported financially by the Fundamental Research Funds for the Central Universities.
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