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Existence of Solution and Positive Solution for a Nonlinear Third-Order -Point BVP
Fixed Point Theory and Applications volume 2010, Article number: 126192 (2010)
Abstract
In this paper, we are concerned with the following nonlinear third-order -point boundary value problem: , , , , . Some existence criteria of solution and positive solution are established by using the Schauder fixed point theorem. An example is also included to illustrate the importance of the results obtained.
1. Introduction
Third-order differential equations arise in a variety of different areas of applied mathematics and physics, for example, in the deflection of a curved beam having a constant or varying cross-section, a three-layer beam, electromagnetic waves, or gravity-driven flows and so on [1].
Recently, third-order two-point or three-point boundary value problems (BVPs) have received much attention from many authors; see [2–10] and the references therein. In particular, Yao [10] employed the Leray-Schauder fixed point theorem to prove the existence of solution and positive solution for the BVP
Although there are many excellent results on third-order two-point or three-point BVPs, few works have been done for more general third-order -point BVPs [11–13]. It is worth mentioning that Jin and Lu [12] studied some third-order differential equation with the following -point boundary conditions:
The main tool used was Mawhin's continuation theorem.
Motivated greatly by [10, 12], in this paper, we investigate the following nonlinear third-order -point BVP:
Throughout, we always assume that and . The purpose of this paper is to consider the local properties of on some bounded sets and establish some existence criteria of solution and positive solution for the BVP (1.3) by using the Schauder fixed point theorem. An example is also included to illustrate the importance of the results obtained.
2. Main Results
Lemma 2.1.
Let . Then, for any , the BVP
has a unique solution
where
Proof.
If is a solution of the BVP (2.1), then we may suppose that
By the boundary conditions in (2.1), we know that
Therefore, the unique solution of the BVP (2.1)
In the remainder of this paper, we always assume that . For convenience, we denote
The following theorem guarantees the existence of solution for the BVP (1.3).
Theorem 2.2.
Assume that is continuous and there exist and such that
Then the BVP (1.3) has one solution satisfying
Proof.
Let be equipped with the norm , where . Then is a Banach space.
Let , . Then the BVP (1.3) is equivalent to the following system:
Furthermore, it is easy to know that the system (2.10) is equivalent to the following system:
Now, if we define an operator by
where
then it is easy to see that is completely continuous and the system (2.11) and so the BVP (1.3) is equivalent to the fixed point equation
Let . Then is a closed convex subset of . Suppose that . Then and . So,
which implies that
From (2.16) and , we have
On the other hand, it follows from (2.17) that
In view of (2.18) and (2.19), we know that
which shows that . Then it follows from the Schauder fixed point theorem that has a fixed point . In other words, the BVP (1.3) has one solution , which satisfies
On the basis of Theorem 2.2, we now give some existence results of nonnegative solution and positive solution for the BVP (1.3).
Theorem 2.3.
Assume that , , , , is continuous, and there exist and such that
Then the BVP (1.3) has one solution satisfying
Proof.
Let
Then is continuous and
Consider the BVP
By Theorem 2.2, we know that the BVP (2.26) has one solution satisfying
Since , we get
In view of (2.28) and , we have
which implies that
It follows from (2.28), (2.30), and the definition of that
Therefore, is a solution of the BVP (1.3) and satisfies
Corollary 2.4.
Assume that all the conditions of Theorem 2.3 are fulfilled. Then the BVP (1.3) has one positive solution if one of the following conditions is satisfied:
(i);
(ii);
(iii), .
Proof.
Since it is easy to prove Cases (ii) and (iii), we only prove Case (i). It follows from Theorem 2.3 that the BVP (1.3) has a solution , which satisfies
Suppose that . Then for any , we have
which shows that is a positive solution of the BVP (1.3).
Example 2.5.
Consider the BVP
where , .
A simple calculation shows that and . Thus, if we choose and , then all the conditions of Theorem 2.3 and (i) of Corollary 2.4 are fulfilled. It follows from Corollary 2.4 that the BVP (2.35) has a positive solution.
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Acknowledgment
This paper was supported by the National Natural Science Foundation of China (10801068).
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Sun, JP., Jin, FX. Existence of Solution and Positive Solution for a Nonlinear Third-Order -Point BVP. Fixed Point Theory Appl 2010, 126192 (2010). https://doi.org/10.1155/2010/126192
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DOI: https://doi.org/10.1155/2010/126192