## Qualitative Analysis of Differential, Difference Equations, and Dynamic Equations on Time Scales

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# Oscillation Theorems for Second-Order Half-Linear Neutral Delay Dynamic Equations with Damping on Time Scales

**Academic Editor:**Tongxing Li

#### Abstract

We establish the oscillation criteria of Philos type for second-order half-linear neutral delay dynamic equations with damping on time scales by the generalized Riccati transformation and inequality technique. Our results are new even in the continuous and the discrete cases.

#### 1. Introduction

In reality, it is known that the movement in the vacuum or ideal state is rare, while the movement with damping and disturbance is extensive. In recent years, the study of the oscillation of the second-order dynamic equations with damping on time scales is emerging; see [1–7], for example. Besides, the study of the oscillation for the second-order linear and nonlinear or semilinear dynamic equations can be found in [8–23] and of the oscillation for the high-order dynamic equations can be found in [24–33]. Then, inspired by the above work, this paper will study the oscillatory behavior of all solutions of a more extensive second-order half-linear neutral delay dynamic equation with damping, which is given as follows: where , , .

Here, we give the following hypotheses at first.(H_{1}) is a time scale (i.e., a nonempty closed subset of the real numbers ) which is unbounded above and when with , we define the time scale interval of the form by .(H_{2}) are positive* rd*-continuous functions such that , where is defined as the set of all regressive and* rd*-continuous functions and is all positively regressive elements of .(H_{3}) is a strictly increasing and differentiable function such that
(H_{4}) is a continuous function such that, for some positive constant ,

The solution of (1) defines a nontrivial real-valued function satisfying (1) for . A solution of (1) is called oscillatory if it is neither eventually positive nor negative; otherwise, it is called nonoscillatory. Equation (1) is called oscillatory if all its solutions are oscillatory. Here, we pay attention to those solutions of (1) which are not the eventually identical zero.

The purpose of this paper is to establish the oscillation criteria of Philos [34] for (1). The two famous results of Philos [34] about oscillation of second-order linear differential equations are extended to (1), while it satisfies Besides, two criteria of (1) about the fact that each solution is either oscillatory or converges to zero are obtained when

The paper is organized as follows. In Section 2, we present some basic definitions and results about the theory of calculus on time scales. In Section 3, we give some lemmas. Section 4 introduces the main results of this paper. We established four new oscillatory criteria when conditions (4) and (5) hold, respectively, for the solutions of (1) in this paper.

#### 2. Some Preliminaries

On the time scale we define the forward and backward jump operators by A point is said to be left-dense if it satisfies , right-dense if it satisfies , left-scattered if it satisfies , and right-scattered if it satisfies . The graininess function of the time scale is defined by . For a function , the (delta) derivative is defined by if is continuous at and is right-scattered. If is right-dense, then the derivative is defined by provided this limit exists. A function is said to be rd-continuous if it is continuous at each right-dense point and if there exists a finite left limit at every left-dense point. Denote by the set of rd-continuous functions , and denote by the set of functions which is -differentiable and the derivative is rd-continuous. The derivative of , the shift of , and the graininess function are related by the following formula:

We will make use of the following product and quotient rules for the derivative of the product and the quotient of two differentiable functions and : For , the Cauchy integral of is defined by The integration by parts formula reads and the infinite integral is defined by For more details, see [8, 9].

#### 3. Several Lemmas

In this section, we present six lemmas that are needed in Section 4. The first lemma is well known, and it can be found in Chapter 2 of [8]. Lemma 2 is Theorem 1.93 of [8]; Lemma 3 is the simple corollary of Theorem 1.90 in [8]; Lemma 4 is Theorem 41 in [35]; and Lemma 5 is Theorem 3 in [36].

Lemma 1. *If , that is, is rd-continuous, such that for all , then the initial value problem has a unique and positive solution on , denoted by . This “exponential function” satisfies the semigroup property .*

Lemma 2. *Assume that is strictly increasing and is a time scale. Let . If and exist on , where
**
then
*

Lemma 3. *If is differentiable, then
*

Lemma 4. *Assume that and are nonnegative real numbers; then
**
where the equality holds if and only if .*

Lemma 5. *Let and . Then for positive rd-continuous functions we have
*

*where and .*

Lemma 6. *Assume that ()–() and (4) hold. Let be an eventually positive solution of (1). Then there exists such that
*

*Proof. *Suppose that is an eventually positive solution of (1). There exists such that and for . From the definition of , we get for , and at the same time for , from (1), we get
Hence, from Lemma 1 and (11) we obtain
for . So
is decreasing. By Lemma 1, is either eventually positive or eventually negative. Therefore, for arbitrary , we have
Otherwise, we assume that (24) is not satisfied; then there exits such that for all . Because (23) is decreasing, from Lemma 1 we have
for , where . By (25) and Lemma 1, we get
that is,
After integrating the two sides of inequality (27) from to , we have
Next, we find the limits of the two sides of (28) when . From (4), we get . Therefore, is eventually negative, which is contradictory to . So the inequality (24) holds.

From (24) and (21), it is obvious that the second inequality of (20) holds. This completes the proof.

#### 4. Main Results

Firstly, the two famous results of Philos [24] about oscillation of second-order linear differential equations are extended to (1) when condition (4) is satisfied.

Theorem 7. *Assume that ()–() and (4) hold. Let , be rd-continuous function, such that
*

*and has a nonpositive continuous -partial derivative with respect to the second variable and satisfies (31). Let be a*

*rd*-continuous function and satisfies*If there exist a positive and differentiable function such that for and a real*

*rd*-continuous function such that*where , , and , then (1) is oscillatory on .*

*Proof. *Assume that (1) has a nonoscillatory solution on . Without loss of generality we may assume that there exists , such that and for all . By the definition of , it follows
Since it satisfies , there exists such that for all . Then if it satisfies , we have
By Lemma 6 and (), we obtain that
on (where is short hand for ), and
holds. Moreover, using Lemmas 3 and 6, it follows that
In Lemma 2, let , and is unbounded above by , so , and by ; using Lemma 2, we get
Thus
By the above inequality and the first inequality in (37), we obtain that
holds on . Now we define the function by
Then we have on , and
then we obtain
on , where . Thus, for every with , by (13), we get
where . So using Lemma 4, let
Using the inequality (18), we have
where . Thus
From (46) and (50), we obtain
that is,
From condition (34), we have
By (46), we have
and from the above inequality, let , and denote that
meanwhile noting (54), we obtain
Now we assert that
holds. Suppose to the contrary that
By (31), there exists a constant such that
From (59), there exists a for arbitrary real number such that
for . By (13), we have
From (60), there exists such that for , so . Since is arbitrary, we have
Selecting a sequence with satisfying
then there exists a constant such that
for sufficiently large positive integer . From (63), we can easily see
and (65) implies that
From (65) and (66), we have
that is,
for sufficiently large positive integer , which together with (67) implies
On the other hand, by Lemma 5, we obtain
The above inequality shows that
Hence, (70) implies
which contradicts (32). Therefore (58) holds. Noting for , by using (58), we obtain
which is contradicting with (33). This completes the proof.

*Remark 8. *From Theorem 7, we can obtain different conditions for oscillation of all solutions of (1) with different choices of and . For example, or .

Theorem 9. *Assume that ()–(), (4), (30)-(31), and (33) hold, where , , , and are defined in Theorem 7. Assume that
**
holds, where , . Then (1) is oscillatory on .*

* Proof. *Assume that (1) has a nonoscillatory solution on . Without loss of generality we may assume that there exists , such that and for all . So and there exists such that
for . Define the function by
We proceed as in the proof of Theorem 7 to obtain (46) and (50), so that
Hence, (76) implies
then we have
From the above inequality and (75), we have
Therefore, there exists a sequence with such that
Definitions of and are as in Theorem 7; from (46), and noting (81), we have
For the above sequence ,
We obtain (58) by using reductio ad absurdum. The rest of the proof is similar to that of Theorem 7 and hence is omitted. This completes the proof.

If (4) is not satisfied, that is, if condition (5) holds, we can obtain the following results.

Theorem 10. *Assume that ()–(), (5), and (30)–(34) hold, where , , , and are defined in Theorem 7. Assume that
**
holds. Then every solution of (1) is either oscillatory or converges to zero on .*

* Proof. *As the proof of Theorem 7, assume that (1) has a nonoscillatory solution on . Without loss of generality we may assume that there exists , such that and for all . So and there exists