Abstract and Applied Analysis

Volume 2012, Article ID 826504, 12 pages

http://dx.doi.org/10.1155/2012/826504

## Positive Solutions for Nonlinear First-Order *m*-Point Boundary Value Problem on Time Scales

Department of Mathematics, Pamukkale University, 20070 Denizli, Turkey

Received 7 August 2012; Accepted 24 October 2012

Academic Editor: Yongfu Su

Copyright © 2012 İsmail Yaslan. 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 means of fixed-point theorems, we investigate the existence of positive solutions for nonlinear first-order -point boundary value problem , , where is a time scale, , are given constants.

#### 1. Introduction

The theory of time scales, which has recently received a lot of attention, was introduced by Stefan Hilger in his Ph.D. thesis in 1988 (see [1]). The time scales calculus has a tremendous potential for applications in some mathematical models of real processes and phenomena studied in physics, chemical technology, population dynamics, biotechnology and economics, neural networks, and social sciences; see the monographs of Aulbach and Hilger [2], Bohner and Peterson [3, 4], and Lakshmikantham et al. [5] and the references therein.

A time scale is an arbitrary nonempty closed subset of real numbers . A book on the subject of time scales by Bohner and Peterson [3] also summarizes and organizes much of the time scale calculus. The closed interval in is defined as where with .

In this study, we consider the nonlinear first-order -point boundary value problem where is a time scale, are given constants. is regressive and rd-continuous, and is continuous.

In [6], Cabada studied the following first-order periodic boundary value problem on time scales: He developed the monotone method in the presence of lower and upper solutions to obtain the existence of extremal solutions. When , and , BVP (1.2) is reduced to (1.3).

In [7], Sun studied the first-order boundary value problem where . Some existence results for at least two positive solutions were established, by using Avery-Henderson fixed-point theorem. When and , BVP (1.2) is reduced to (1.5).

In [8], Shu and Chunhua are concerned with the existence of three positive solutions for the following nonlinear first-order boundary value problem on time scale: where is fixed, , and is continuous. When and , BVP (1.2) is reduced to (1.5).

Sun and Li [9] studied the following first-order periodic boundary value problem on time scales: Conditions for the existence of at least one solution were obtained by using novel inequalities and the Schaefer fixed-point theorem. When and , BVP (1.2) is reduced to (1.6).

In [10], Tian and Ge studied the existence and uniqueness results for first-order three-point boundary value problem by using several well-known fixed-point theorems. When , BVP (1.2) is reduced to (1.7).

Motivated by [6–10], we establish some new and more general results for the existence of positive solutions for the problem (1.2) by applying fixed-point theorems in cones.

We have arranged the paper as follows. In Section 2, we give some lemmas which are needed later. In Section 3, we apply the Krasnosel'skii fixed-point theorem, Avery-Henderson fixed-point theorem, and Leggett-Williams fixed-point theorem to prove the existence of at least one, two, and three positive solutions to BVP (1.2). In Section 4, as an application, the examples are included to illustrate our results.

#### 2. Preliminaries

Let denote the Banach space with the norm . For , we consider the following linear boundary value problem:

Lemma 2.1. * For , BVP (2.1) has the unique solution
**
where .*

*Proof. * From , we have
By using the boundary condition, we get
Thus, satisfies (2.2).

Let be Green's function for the boundary value problem By Lemma 2.1, we obtain where for all .

Lemma 2.2. *Green's function in (2.6) has the following properties:*(i)* for .*(ii)*, where and .*(iii)* for .*

Let denote the Banach space with the norm . Define the cone by Equation (1.2) is equivalent to the nonlinear integral equation

We can define the operator by Therefore solving (2.9) in is equivalent to finding fixed-points of the operator .

From Lemma 2.2, for . In addition, by using Lemma 2.2 we get

So, we have .

#### 3. Main Results

To prove the existence of at least one positive solution for the BVP (1.2), we will need the following (Krasnosel'skii) fixed-point theorem.

Theorem 3.1 (Krasnosel'skii fixed-point theorem [11]). *Let be a Banach space, and let be a cone. Assume and are open bounded subsets of with , , and let
**
be a completely continuous operator such that either*(i)* for for , or*(ii)* for for hold. Then A has a fixed-point in . *

Theorem 3.2. * Let there exist numbers , satisfying such that for **
Then BVP (1.2) has at least one positive solution satisfying , .*

*Proof. *It is easy to check by the Arzela-Ascoli theorem that the operator is completely continuous. Let us now define two bounded open sets as follows:
Then . For , we obtain
Hence for .

If , then and for . We have

Thus for . By the first part of Theorem 3.1, has a fixed-point in . Therefore, the BVP (1.2) has at least one positive solution satisfying , .

Now, we will apply the following (Avery-Henderson) fixed-point theorem to prove the existence of at least two positive solutions to BVP (1.2).

Theorem 3.3 (see [12]). * Let be a cone in a real Banach space . Set
**
If and are increasing, nonnegative continuous functionals on , let be a nonnegative continuous functional on with such that, for some positive constants and ,
**
for all . Suppose that there exist positive numbers such that
**
If is a completely continuous operator satisfying*(i)* for all ,*(ii)* for all ,*(iii)* and for all ,** then has at least two fixed-points and such that
*

Theorem 3.4. *Suppose there exist numbers , , and satisfying such that the function satisfies the following conditions:*(i)* for and ;*(ii)* for and ;*(iii)* for and .** Then the BVP (1.2) has at least two positive solutions and such that
*

*Proof . *Let the nonnegative increasing continuous functionals , , and be defined on the cone by
For each , we have and
Then . In addition, and for all , we obtain .

Now we will verify the remaining conditions of Theorem 3.3.* Claim **1*. If , then . Since , we have for . Then, we get
by hypothesis .* Claim **2.* If , then . Since , for . Thus, by hypothesis we have
*Claim **3. * and for all . Since and , . If , we get for . Hence, we obtain
by hypothesis . This completes the proof.

To prove the existence of at least three positive solutions for the BVP (1.2), we will apply the following (Leggett-Williams) fixed-point theorem.

Theorem 3.5 (see [13]). *Let P be a cone in the real Banach space . Set
**
Suppose is a completely continuous operator and is a nonnegative continuous concave functional on with for all . If there exists such that the following condition hold:*(i)* and for all ;*(ii)* for ;*(iii)* for with ,** then has at least three fixed-points , and in satisfying
*

Theorem 3.6. *Suppose that there exist numbers , , and satisfying such that for the function satisfies the following conditions:*(i)*, ,*(ii)*, ,*(iii)*, .** Then (1.2) has at least three positive solutions , and satisfying
*

*Proof. *Define the nonnegative continuous concave functional to be and the cone as in (2.8). For all , we have . If , then and from the hypothesis . Then we get
by Lemma 2.2. This proves that . Similarly, by the hypothesis , the condition of Theorem 3.5 is satisfied.

Since and , . For all , we have for . Using the hypothesis and Lemma 2.2, we find
Hence, the condition of Theorem 3.5 holds.

For the condition of Theorem 3.5, we suppose that with . Then, from Lemma 2.2 we obtain
This completes the proof.

#### 4. Examples

*Example 4.1. *Let . We consider the first-order four-point BVP as follows:
Taking , we have , and . If we take , and ; then all the assumptions in Theorem 3.4 are satisfied. Finally, BVP (4.1) has at least two positive solutions and such that

*Example 4.2. *Let . We consider the first-order four-point BVP as follows:
where , and
Hence, we obtain , and . If we take , and ; then all the assumptions in Theorem 3.6 are satisfied. Finally, BVP (4.3) has at least three positive solutions , and such that

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