Oscillation for Second-Order Nonlinear Delay Dynamic Equations on Time Scales
© Zhenlai Han et al. 2009
Received: 6 December 2008
Accepted: 25 May 2009
Published: 29 June 2009
By means of Riccati transformation technique, we establish some new oscillation criteria for the second-order nonlinear delay dynamic equations on a time scale ; here is a quotient of odd positive integers with and real-valued positive rd-continuous functions defined on . Our results not only extend some results established by Hassan in 2008 but also unify the oscillation of the second-order nonlinear delay differential equation and the second-order nonlinear delay difference equation.
The theory of time scales, which has recentlyreceived a lot of attention, was introduced by Hilger in his Ph.D. Thesis in 1988 in order to unify continuous and discrete analysis (see Hilger ). Several authors have expounded on various aspects of this new theory; see the survey paper by Agarwal et al.  and references cited therein. A book on the subject of time scales, by Bohner and Peterson , summarizes and organizes much of the time scale calculus. We refer also to the last book by Bohner and Peterson  for advances in dynamic equations on time scales. For the notation used hereinafter we refer to the next section that provides some basic facts on time scales extracted from Bohner and Peterson .
A time scale is an arbitrary closed subset of the reals, and the cases when this time scale is equal to the reals or to the integers represent the classical theories of differential and of difference equations. Many other interesting time scales exist, and they give rise to plenty of applications, among them the study of population dynamic models which are discrete in season (and may follow a difference scheme with variable step-size or often modeled by continuous dynamic systems), die out, say in winter, while their eggs are incubating or dormant, and then in season again, hatching gives rise to a nonoverlapping population (see Bohner and Peterson ). Not only does the new theory of the so-called "dynamic equations" unify the theories of differential equations and difference equations but also it extends these classical cases to cases "in between", for example, to the so-called -difference equations when (which has important applications in quantum theory) and can be applied on different types of time scales like , and the space of the harmonic numbers.
In recent years, there has been much research activity concerning the oscillation and nonoscillation of solutions of various equations on time scales, and we refer the reader to Bohner and Saker , Erbe , and Hassan . However, there are few results dealing with the oscillation of the solutions of delay dynamic equations on time scales [8–15].
We assume that is a quotient of odd positive integers, and are positive, real-valued rd-continuous functions defined on , is strictly increasing, and is a time scale, and as , which satisfies for some positive constant , for all nonzero .
and established some sufficient conditions for oscillation of (1.2).
where and , is continuous and nondecreasing , and for , and they established the equivalence of the oscillation of (1.3) and (1.4), from which obtained some oscillation criteria and comparison theorems for (1.3). However, the results established in  are valid only when the graininess function is bounded which is a restrictive condition. Also the restriction is required.
then every solution of (1.5) oscillates. Now, we observe that the condition (1.6) depends on an additional constant which implies that the results are not sharp (see Erbe et al. ).
established some sufficient conditions for oscillation of (1.7), and extended the results given in .
where and are positive, real-valued rd-continuous functions defined on , is rd-continuous, and as , and such that satisfies for some positive constant , , for all nonzero , and they extended the generalized Riccati transformation techniques in the time scales setting to obtain some new oscillation criteria which improve the results given by Zhang and Shanliang  and Sahiner .
Clearly, (1.2), (1.3), (1.5), and (1.8) are the special cases of (1.1). In this paper, we consider the second-order nonlinear delay dynamic equation on time scales (1.1).
As we are interested in oscillatory behavior, we assume throughout this paper that the given time scale is unbounded above. We assume , and it is convenient to assume We define the time scale interval of the form by .
The paper is organized as follows. In Section 2, we intend to use the Riccati transformation technique, a simple consequence of Keller's chain rule, and an inequality to obtain some sufficient conditions for oscillation of all solutions of (1.1). In Section 3, we give an example in order to illustrate the main results.
2. Main Results
where is delta differentiable and eventually positive or eventually negative, which is a simple consequence of Keller's chain rule (see Bohner and Peterson [3, Theorem 1.90]). Also, we need the following auxiliary result.
The proof is similar to that of Hassan [7, Lemma 2.1], and so is omitted.
Lemma 2.2 (Chain Rule).
The proof is completed.
which contradicts (2.7). The proof is completed.
which contradicts (2.24). This completes the proof.
From the proof of Lemma 2.1, we see that there exist two possible cases for the sign of . The proof when is an eventually positive is similar to that of the proof of Theorem 2.3 or Theorem 2.5, and hence it is omitted.
3. Application and Example
Theorem 3.1 (Hassan [7, Theorem 2.1]).
We note that (1.1) becomes (3.1) when , and Theorem 2.3 becomes Theorem 3.1, and so Theorem 2.3 in this paper essentially includes results of Hassan [7, Theorem 2.1].
Similarly, Theorem 2.5 includes results of Hassan [7, Theorem 2.2], and Theorem 2.6 includes results of Hassan [7, Theorem 2.4]. One can easily see that nonlinear delay dynamic equations (1.8) considered by Erbe et al.  are the special cases of (1.1), and the results obtained in  cannot be applied in (1.1), and so our results are new.
We conclude that (3.3) is oscillatory.
The authors sincerely thank the reviewers for their valuable suggestions and useful comments that have lead to the present improved version of the original manuscript. This research is supported by the Natural Science Foundation of China (60774004), China Postdoctoral Science Foundation Funded Project (20080441126), Shandong Postdoctoral Funded Project (200802018) and supported by Shandong Research Funds (Y2008A28), and also supported by the University of Jinan Research Funds for Doctors (B0621, XBS0843).
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