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Monotone Iterative Technique for FirstOrder Nonlinear Periodic Boundary Value Problems on Time Scales
Advances in Difference Equations volume 2010, Article number: 620459 (2010)
Abstract
We investigate the following nonlinear firstorder periodic boundary value problem on time scales: , , . Some new existence criteria of positive solutions are established by using the monotone iterative technique.
1. Introduction
Recently, periodic boundary value problems (PBVPs for short) for dynamic equations on time scales have been studied by several authors by using the method of lower and upper solutions, fixed point theorems, and the theory of fixed point index. We refer the reader to [1–10] for some recent results.
In this paper we are interested in the existence of positive solutions for the following firstorder PBVP on time scales:
where will be defined in Section 2, is a time scale, is fixed and . For each interval of we denote by By applying the monotone iterative technique, we obtain not only the existence of positive solution for the PBVP (1.1), but also give an iterative scheme, which approximates the solution. It is worth mentioning that the initial term of our iterative scheme is a constant function, which implies that the iterative scheme is significant and feasible. For abstract monotone iterative technique, see [11] and the references therein.
2. Some Results on Time Scales
Let us recall some basic definitions and relevant results of calculus on time scales [12–15].
Definition 2.1.
For we define the forward jump operator by
while the backward jump operator is defined by
In this definition we put and where denotes the empty set If we say that is right scattered, while if we say that is left scattered. Also, if and then is called right dense, and if and then is called left dense. We also need below the set which is derived from the time scale as follows. If has a leftscattered maximum then Otherwise,
Definition 2.2.
Assume that is a function and let Then is called differentiable at if there exists a such that, for any given there is an open neighborhood of such that
In this case, is called the delta derivative of at and we denote it by If then we define the integral by
Definition 2.3.
A function is called rdcontinuous provided that it is continuous at rightdense points in and its leftsided limits exist at leftdense points in The set of rdcontinuous functions will be denoted by
Lemma 2.4 (see [13]).
If and then
where is the graininess function.
Lemma 2.5 (see [13]).
If then is increasing.
Definition 2.6.
For we define the Hilger complex numbers as
and for let
Definition 2.7.
For let be the strip
and for let
Definition 2.8.
For we define the cylinder transformation by
where is the principal logarithm function. For we define for all
Definition 2.9.
A function is regressive provided that
The set of all regressive and rdcontinuous functions will be denoted by
Definition 2.10.
We define the set of all positively regressive elements of by
Definition 2.11.
If , then the generalized exponential function is given by
where the cylinder transformation is defined as in Definition 2.8.
Lemma 2.12 (see [13]).
If , then

(i)
,

(ii)
,

(iii)
,

(iv)
for and
Lemma 2.13 (see [13]).
If and , then
3. Main Results
For the forthcoming analysis, we assume that the following two conditions are satisfied.
(H1) is rdcontinuous, which implies that .
(H2) is continuous and is nondecreasing on .
If we denote that
then we may claim that , which implies that
In fact, in view of (H1) and Lemmas 2.12 and 2.13, we have
which together with Lemma 2.5 shows that is increasing on And so,
This indicates that .
Let
be equipped with the norm Then is a Banach space.
First, we define two cones and in as follows:
and then we define an operator
It is obvious that fixed points of are solutions of the PBVP (1.1).
Since is nondecreasing on , we have the following lemma.
Lemma 3.1.
is nondecreasing.
Lemma 3.2.
is completely continuous.
Proof.
Suppose that Then
so,
Therefore,
This shows that . Furthermore, with similar arguments as in [7], we can prove that is completely continuous by ArzelaAscoli theorem.
Theorem 3.3.
Assume that there exist two positive numbers such that
Then the PBVP (1.1) has positive solutions and , which may coincide with
where and for .
Proof.
First, we define
Then we may assert that
In fact, if , then
which together with (H2) and (3.10) implies that
which shows that
Now, if we denote that for , then . Let
In view of , we have Since the set is bounded and the operator is compact, we know that the set is relatively compact, which implies that there exists a subsequence such that
Moreover, since
it follows from Lemma 3.1 that ; that is, . By induction, it is easy to know that
which together with (3.18) implies that
Since is continuous, it follows from (3.17) and (3.21) that
which shows that is a solution of the PBVP (1.1). Furthermore, we get from that
On the other hand, if we denote that for and that then we can obtain similarly that and there exists a subsequence such that
Moreover, since
it is also easy to know that
With the similar arguments as above, we can prove that is a solution of the PBVP (1.1) and satisfies
Corollary 3.4.
If the following conditions are fulfilled:
then there exist two positive numbers such that (3.10) is satisfied, which implies that the PBVP (1.1) has positive solutions and , which may coincide with
where and for .
Example 3.5.
Let We consider the following PBVP on :
Since and we can obtain that
Thus, if we choose and , then all the conditions of Theorem 3.3 are fulfilled. So, the PBVP (3.30) has positive solutions and , which may coincide with
where and for .
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Acknowledgment
This work was supported by the National Natural Science Foundation of China (10801068).
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Zhao, YH., Sun, JP. Monotone Iterative Technique for FirstOrder Nonlinear Periodic Boundary Value Problems on Time Scales. Adv Differ Equ 2010, 620459 (2010). https://doi.org/10.1155/2010/620459
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DOI: https://doi.org/10.1155/2010/620459
Keywords
 Periodic Boundary
 Point Theorem
 Open Neighborhood
 Iterative Scheme
 Point Index