Research Article | Open Access

# Eigenvalue of Fractional Differential Equations with -Laplacian Operator

**Academic Editor:**Fuyi Xu

#### Abstract

We investigate the existence of positive solutions for the fractional order eigenvalue problem with -Laplacian operator , where are the standard Riemann-Liouville derivatives and -Laplacian operator is defined as is continuous and can be singular at and By constructing upper and lower solutions, the existence of positive solutions for the eigenvalue problem of fractional differential equation is established.

#### 1. Introduction

Differential equations of fractional order have been recently proved to be valuable tools in the modeling of many phenomena arising from science and engineering, such as viscoelasticity, electrochemistry, control, porous media, and electromagnetism. For detail, see the monographs of Kilbas et al. [1], Miller and Ross [2], and Podlubny [3] and the papers [4–23] and the references therein.

In [16], the authors investigated the nonlinear nonlocal boundary value problem: where . By using Krasnoselskii's fixed point theorem and the Leggett-Williams theorem, some sufficient conditions for the existence of positive solutions to the above BVP are obtained. In [17], by using the upper and lower solutions method, under suitable monotone conditions, the authors investigated the existence of positive solutions to the following nonlocal problem: where . Recently, by means of the fixed point theorem on cones, Chai [18] investigated two-point boundary value problem of fractional differential equation with -Laplacian operator: Some existence and multiplicity results of positive solutions are obtained.

As far as we know, no result has been obtained for the existence of positive solution for the fractional order eigenvalue problem with -Laplacian operator: where , , are the standard Riemann-Liouville derivatives with with , -Laplacian operator is defined as can be singular at , and . In order to obtain the existence of positive solutions of the fractional order eigenvalue problem (4), we will apply the upper and lower solutions method associated with the Schauder's fixed point theorem. It is worth emphasizing that the problem (4) not only includes the well-known Sturm-Liouville boundary value problems and the nonlocal boundary value problems as special case, but also can be singular at and .

The organization of this paper is as follows. In Section 2, we present some necessary definitions and preliminary results that will be used to prove our main results. In Section 3, we put forward and prove our main results. Finally, we will give an example to demonstrate our main results.

#### 2. Preliminaries and Lemmas

In this section, we introduce some preliminary facts which are used throughout this paper.

*Definition 1 (see [1–3]). *The Riemann-Liouville fractional integral of order of a function is given by
provided that the right-hand side is pointwise defined on .

*Definition 2 (see [1–3]). *The Riemann-Liouville fractional derivative of order of a function is given by
where and denotes the integer part of number , provided that the right-hand side is pointwise defined on .

Proposition 3 (see [1–3]). *(1) If , , then
**(2) If , , then
*

Proposition 4 (see [1–3]). *Let , and is integrable, then
**
where and is the smallest integer greater than or equal to . *

*Definition 5. *A continuous function is called a lower solution of the BVP (4), if it satisfies

*Definition 6. *A continuous function is called an upper solution of the BVP (4), if it satisfies

For forthcoming analysis, we first consider the following linear fractional differential equation:

Lemma 7 (see [15]). *If and , then the boundary value problem (12) has the unique solution
**
where
**
is the Green function of the boundary value problem (12) and
*

Lemma 8. *The Green function in Lemma 7 has the following properties:*(i)* is continuous on ;*(ii)* for any ;*(iii)*, for , where
*

Let satisfy the relation , where is given by (4). To study BVP (4), we first consider the associated linear BVP: for and . For convenience, let then we have the following lemma.

Lemma 9. *The associated linear BVP (17) has the unique positive solution
*

* Proof. *In fact, let . By Proposition 4, the solution of initial value problem
is given by . From the relations , it follows that , and so
Noting that , it follows from (21) that the solution of (17) satisfies
By Lemma 7, the solution of (22) can be written as
Since , , we have , , which implies that the solution of (22) is given by

The following lemma is a straightforward conclusion of Lemma 9.

Lemma 10. *If satisfies
**
and for any , then , for .*

#### 3. Main Results

Set

We present the following two assumptions.

is continuous and decreasing in .

For any , and

Let , and Clearly, , so is nonempty. For any , define an operator by

Theorem 11. *Suppose conditions and hold. In addition, if the following condition holds: **
for uniformly holds. Then there exists a constant such that the BVP (4) has at least one positive solution for any , and there exists one positive constant 1 such that
*

* Proof. *The proof is divided into four steps. *Step 1*. We show that is well defined on and , and is decreasing in .

In fact, for any , by the definition of , there exists two positive numbers such that for any . It follows from Lemma 8 and (H1)-(H2) that

Now take , by , for any , . Thus by the continuity of and Lemma 8 and (32), we have

Take
then by (32) and (33),
which implies that is well defined and . And the operator is decreasing in from . Moreover, by direct computations, we also have
*Step 2*. In this step, we will focus on lower and upper solutions of the fractional boundary value problem (4).

By Lemma 8, we have
Let
it follows from (37) that

On the other hand, take
then by monotonicity of in and (37)–(40), for any , we have
From , we have
uniformly on . Thus there exists large enough , such that, for any ,
which yields
Letting
and by Lemma 9, (39), (44), and (45), one has

By Step 1 and (46), (47), we know . And it follows from (45)–(47) that
Consequently, it follows from (44)–(48) that
that is, and are a couple of lower and upper solutions of fractional boundary value problem (4) by (46)–(49), respectively. *Step 3*. Let
It follows from and (46) that is continuous.

We will show that the fractional boundary value problem
has a positive solution.

To see this, we consider the operator defined as follows:
Obviously, a fixed point of the operator is a solution of the BVP (51). Noting that , then there exists a constant such that . Thus for all , it follows from Lemma 8, (50), and that
which implies that the operator is uniformly bounded.

From the uniform continuity of and the Lebesgue dominated convergence theorem, we easily obtain that is equicontinuous. Thus by the means of the Arzela-Ascoli theorem, we have that is completely continuous. The Schauder fixed point theorem implies that has at least a fixed point such that . *Step 4*. We will prove that the boundary value problem (4) has at least one positive solution.

In fact, we only need to prove that
By (46), (47) and noticing that is fixed point of , we know that
Notice that the definition of and the function is nonincreasing in , we obtain
So by (48) and (56),
Thus one has by (57)
Let ; then
and (55) implies that . It follows from (21) that
and then
Notice that is monotone increasing; we have
It follows from Lemma 10 and (55) that
Thus we have on . By the same way, we also have on . So
Consequently, . Then is a positive solution of the problem (4).

Finally, by (48) and (64) and , we have
where

In the end of this work we also remark the above results to the problem (4) with which is nonsingular at and ; that is, we have the following result.

Theorem 12. *If is continuous, decreasing in and , for any , then the boundary value problem (4) has at least one positive solution for any , and there exists a constant such that
*

* Proof. *The proof is similar to Theorem 11; we omit it here.

*Example 13. *Consider the following boundary value problem:

Let , , , , and Firstly, And, it is easy to check that holds. For any , and which implies that holds.

On the other hand, Thus also holds.

By Theorem 11, the boundary value problem (68) has at least one positive solution.

#### Acknowledgments

This work was supported by the Natural Sciences of Education and the Science Office Bureau of Sichuan Province of China, under Grants nos. 10ZC060, 2010JY0J41.

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#### Copyright

Copyright © 2013 Wenquan Wu and Xiangbing Zhou. 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.