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Abstract and Applied Analysis

VolumeÂ 2012Â (2012), Article IDÂ 743469, 20 pages

http://dx.doi.org/10.1155/2012/743469

## Oscillation Criteria for Second-Order Nonlinear Dynamic Equations on Time Scales

^{1}Department of Mathematics, Guangdong University of Finance, 527 Yingfu Lu, Guangdong, Guangzhou 510520, China^{2}School of Mathematics & Computational Science, Sun Yat-Sen University, 135 Xinguang Xi Lu, Guangdong, Guangzhou 510275, China

Received 31 August 2012; Accepted 15 October 2012

Academic Editor: ZhanbingÂ Bai

Copyright Â© 2012 Shao-Yan Zhang and Qi-Ru Wang. 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

This paper is concerned with oscillation of second-order nonlinear dynamic equations of the form on time scales. By using a generalized Riccati technique and integral averaging techniques, we establish new oscillation criteria which handle some cases not covered by known criteria.

#### 1. Introduction

The theory of time scales was introduced by Stefan Hilger in his Ph.D. thesis in 1988 in order to unify continuous and discrete analysis. Not only can this theory of the so-called â€œdynamic equations" unify theories of differential equations and difference equations but also extend these classical cases to cases â€œin between", for example, to the so-called -difference equations. A time scale is an arbitrary nonempty closed subset of the real numbers with the topology and ordering inherited form , and the cases when this time scale is equal to or to the integers represent the classical theories of differential and difference equations. Of course many other interesting time scales exist, and they give rise to plenty of applications. In recent years, there has been much research activity concerning the oscillation and nonoscillation of solutions of various dynamic equations on time scales, we refer the reader to [1â€“14].

In 2006, Wu et al. [1] considered the second-order nonlinear neutral dynamic equation with variable delays where is a quotient of odd positive integers. In 2007, Saker et al. [2] also discussed (1.1) for an odd positive integer . In 2010, Zhang and Wang [3] extended and complemented some results in [1, 2] for and gave some new results for . In 2011, Saker [4] considered (1.1) in different conditions. In 2010, Sun et al. [5] considered the second-order quasiliner neutral delay dynamic equation where , , and are quotients of odd positive integers with .

In this paper, we study the second-order nonlinear dynamic equation on a time scale , where , is a quotient of odd positive integers.

The paper is organized as follows. In the next section, we give some preliminaries and lemmas. In Section 3, we will use the Riccati transformation technique to prove our main results. In Section 4, we present two examples to illustrate our results.

#### 2. Preliminaries and Lemmas

For convenience, we recall some concepts related to time scales. More details can be found in [6].

*Definition 2.1. *Let be a time scale, for the forward jump operator is defined by , the backward jump operator by , and the graininess function by , where and . If , is said to be right-scattered, otherwise, it is right-dense. If , is said to be left-scattered, otherwise, it is left-dense. The set is defined as follows. If has a left-scattered maximum , then , otherwise, .

*Definition 2.2. *For a function and , one defines the delta-derivative of to be the number (provided it exists) with the property that given any , there is a neighborhood of (i.e., for some ) such that
We say that is delta-differentiable (or in short, differentiable) on provided exists, for all .

It is easily seen that if is continuous at and is right-scattered, then is differentiable at with Moreover, if is right-dense then is differential at if the limit exists as a finite number. In this case In addition, if , then is nondecreasing. A useful formula is We will make use of the following product and quotient rules for the derivative of the product and the quotient (where ) of two differentiable functions and :

*Definition 2.3. *Let be a function, is called right-dense continuous (rd-continuous) if it is continuous at right-dense points in and its left-sided limits exist (finite) at left-dense points in . A function is called an antiderivative of provided holds for all . By the antiderivative, the Cauchy integral of is defined as , and .

Let denote the set of all rd-continuous functions mapping to . It is shown in [6] that every rd-continuous function has an antiderivative. An integration by parts formula is
In (1.3), we assume that is a time scale and, , , , and , ,, , , where , is continuous function such that for all , there exist (), quotients of odd positive integers and such that , , and .

Since we are interested in the oscillatory and asymptotic behavior of solutions near infinity, we assume throughout that the time scale under consideration satisfies and . For , let . Throughout this paper, these assumptions will be supposed to hold. Let , and . Clearly for , is nondecreasing and coincides with the inverse of when the latter exists.

By a solution of (1.3), we mean a nontrivial real-valued function which has the properties and . Our attention is restricted to those solutions of (1.3) that exist on some half line and satisfy for any . A solution of (1.3) is said to be oscillatory if it is neither eventually positive nor eventually negative. Otherwise it is called nonoscillatory. The equation itself is called oscillatory if all its solutions are oscillatory.

For convenience, we use the notation , and , and set Then (1.3) becomes Now, we give the first lemma. Set

Lemma 2.4. *Let conditions hold. If is an eventually positive solution of (1.3), then there exists sufficiently large such that , , , and () for .*

*Proof. *If is an eventually positive solution of (1.3), then by there exists a such that
From (2.8), (1.3), and , we see that . Also by (1.3) and , we have
which implies that is decreasing on .

We claim that on . Assume not, there is a such that . Since for , we have
Integrating the inequality above form to , by we get
and this contradicts the fact that , for all . Thus we have on and so on .

Note that
we have
Since and , we get
The proof is complete.

*Remark 2.5. *By on , , (1.3), (2.8) and , we get

Lemma 2.6 (see [3]). *Let , where and B are constants, is a quotient of odd positive integers. Then attains its maximum value on at , and
*

Lemma 2.7 (see [11]). * and are delta-differentiable on . For and any , one has
*

#### 3. Main Results

In this section, by employing the Riccati transformation technique we will establish oscillation criteria for (1.3) in two cases: and . Set .

Theorem 3.1. *Assume that hold and . Furthermore, assume that there exists a positive rd-continuous -differentiable function such that for all sufficiently large ,
**
then (1.3) is oscillatory.*

*Proof. *Suppose to the contrary that is a nonoscillatory solution of (1.3). Without loss of generality, we may assume that is eventually positive (note that in the case when is eventually negative, the proof is similar, since the substitution transforms (1.3) into the same form). Then, by there exists sufficiently large such that , , , and Lemma 2.4 holds for , where is defined by (2.8). Define the function by the Riccati substitution
then and
By (1.3), , and (2.18), we obtain
Noting that , we have
By Youngâ€™s inequality
with
we have
By and Lemma 2.4, we get
In view of and (3.5)â€“(3.10), for all , we obtain
Using , Lemma 2.4 and the Kellerâ€™s chain rule, we get
Also from Lemma 2.4 and , we have
By (3.11)â€“(3.13), we get
Setting
then by Lemma 2.6, from (3.14) we obtain that for all ,
Integrating the above inequality from to , we get
Taking lim sup on both sides of the above inequality as , we obtain a contradiction to condition (3.2). The proof is complete.

The following theorem gives new oscillation criteria for (1.3) which can be considered as the extension of Philos-type oscillation criterion. Define and

Theorem 3.2. *Assume that hold and . Furthermore, assume that there exist a positive rd-continuous -differentiable function and a function such that for all sufficiently large ,
**
then (1.3) is oscillatory.*

*Proof. *Suppose to the contrary that is a nonoscillatory solution of (1.3). Without loss of generality, we may assume that is eventually positive. Then, by there exists sufficiently large such that , , , and Lemma 2.4 holds for , where is defined by (2.8). Define as in (3.3). Proceeding as in the proof of Theorem 3.1, we can get (3.14). From (3.14), for function and all we have
Using the integration by parts formula (2.7), we obtain
It follows that
Setting
by Lemma 2.6 we obtain that for all ,
That is,
Taking lim sup on both sides of the above inequality as , we obtain a contradiction to condition (3.19). The proof is complete.

Theorem 3.3. *Assume that hold and . Then (1.3) is oscillatory if for all sufficiently large ,
*

*Proof. *Suppose to the contrary that is a nonoscillatory solution of (1.3). Without loss of generality, we may assume that is eventually positive. Then, by there exists sufficiently large such that , , , and Lemma 2.4 holds for , where is defined by (2.8). Set . By Lemma 2.4, we get . Using and the kellerâ€™s chain rule, we get
So we have and there is a constant such that for . Then (1.3) becomes . By (2.18), we have
Similar to the proof of (3.10), we get
Using the Kellerâ€™s chain rule and , we get and
From and , it follows that
By Lemma 2.4, we get
It follows that
Integrating the above inequality from to , we obtain
Taking lim sup on both sides of the above inequality as , we obtain a contradiction to condition (3.26). The proof is complete.

Theorem 3.4. *Assume that hold and . Furthermore, assume that there exists a positive rd-continuous -differentiable function such that for all sufficiently large ,
**
then (1.3) is oscillatory.*

*Proof. *Suppose to the contrary that is a nonoscillatory solution of (1.3). Without loss of generality, we may assume that is eventually positive. Then, by there exists sufficiently large such that , , , and Lemma 2.4 holds for , where is defined by (2.8). Define as in (3.3). By (2.6), we obtain
By Lemma 2.4, , and (3.5)â€“(3.13), for all we obtain
It follows that
By completing the square, we have
Integrating the above inequality from to , we get
Taking lim sup on both sides of the above inequality as , we obtain a contradiction to condition (3.35). The proof is complete.

Theorem 3.5. *Assume that and hold. Furthermore, assume that there exist a positive rd-continuous -differentiable function and a function such that for all sufficiently large ,
**
then (1.3) is oscillatory.*

*Proof. *By (3.39), the proof is similar to Theorems 3.2 and 3.4, so we omit it.

Theorem 3.6. *Assume that hold and . Furthermore, assume that there exists a rd-continuous -differentiable function such that for all sufficiently large ,
**
then (1.3) is oscillatory.*

*Proof. *Suppose to the contrary that is a nonoscillatory solution of (1.3). Without loss of generality, we may assume that is eventually positive. Then, by there exists sufficiently large such that , , , and Lemma 2.4 holds for , where is defined by (2.8). Define the function by the Riccati substitution
then . From (3.5) and (3.10), it follows that for all
By (3.12) and Lemma 2.7, we obtain
It follows from Lemma 2.4 that
Integrating the above inequality from to , we get
Taking lim sup on both sides of the above inequality as , we obtain a contradiction to condition (3.42). The proof is complete.

From Theorem 3.6, we can establish different sufficient conditions for the oscillation of (1.3) by using different choices of . For instance, if or , we have the following results.

Corollary 3.7. *Assume that hold and . Then (1.3) is oscillatory if for all sufficiently large ,
*

Corollary 3.8. *Assume that hold and . Then (1.3) is oscillatory if for all sufficiently large ,
**
where .**.**
Theoremâ€‰â€‰. Assume that hold and . Furthermore, assume that there exists a positive rd-continuous -differentiable function such that for all sufficiently large ,
**
then (1.3) is oscillatory.*

*Proof. *Suppose to the contrary that is a nonoscillatory solution of (1.3). Without loss of generality, we may assume that is eventually positive. Then, by there exists sufficiently large such that , , and Lemma 2.4 holds for , where is defined by (2.8). Define as in (3.3). Proceeding as in the proof of Theorem 3.1, we get
Using , Lemma 2.4 and the Kellerâ€™s chain rule, we get
By (3.10), (3.51), and (3.52), we get
Since
it follows that
It is easy to see (3.55) is of the same form as (3.14). The following is similar to the proof of Theorem 3.1 and hence omitted.

For , Theorem 3.2 also holds. Its proof is similar to those of Theoremsâ€‰â€‰ and 3.2.

Theoremâ€‰â€‰. *Assume that ** hold and **. Furthermore, assume that there exist a positive *rd*-continuous **-differentiable function ** and a function ** such that for all sufficiently large *,
*then (1.3) is oscillatory. *

Theoremâ€‰â€