Interval Oscillation Criteria for Super-Half-Linear Impulsive Differential Equations with Delay
Abstract
We study the following second-order super-half-linear impulsive differential equations with delay [r(t)φγ(x′(t))]′ + p(t)φγ(x(t − σ)) + q(t)f(x(t − σ)) = e(t), t ≠ τk, x(t+) = akx(t), x′(t+) = bkx′(t), t = τk, where t ≥ t0 ∈ ℝ, φ*(u) = |u|*−1u, σ is a nonnegative constant, {τk} denotes the impulsive moments sequence with τ1 < τ2 < ⋯<τk < ⋯, lim k→∞τk = ∞, and τk+1 − τk > σ. By some classical inequalities, Riccati transformation, and two classes of functions, we give several interval oscillation criteria which generalize and improve some known results. Moreover, we also give two examples to illustrate the effectiveness and nonemptiness of our results.
1. Introduction
A solution of (1.1) is said to be nonoscillatory if it is eventually positive or eventually negative. Otherwise, this solution is said to be oscillatory.
Impulsive differential equation is an adequate mathematical apparatus for the simulation of processes and phenomena observed in control theory, physics, chemistry, population dynamics, biotechnologies, industrial robotics, economics, and so forth. Because it has more richer theory than its corresponding nonimpulsive differential equation, much research has been done on the qualitative behavior of certain impulsive differential equations (see [1, 2]).
In the last decades, there has been an increasing interest in obtaining sufficient conditions for oscillation and/or nonoscillation of different classes impulsive differential equations with delay (constant or variable), see, for example, [1–9] and the references cited therein.
In recent years, interval oscillation of impulsive differential equations was also arousing the interest of many researchers, see [10–15].
Motivated mainly by [16], in this paper, we study the interval oscillation of the delay impulsive equation (1.1). By using classical inequalities, Riccati transformation, and two classes of functions (introduced first by Philos [19]), we establish some interval oscillation criteria which generalize and improve some known results of [13, 16–18]. Moreover, we also give two examples to illustrate the effectiveness and nonemptiness of our results.
2. Main Results
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(A1 r(t) ∈ C([t0, ∞), (0, ∞)) and is nondecreasing, p(t), q(t), e(t) ∈ PLC([t0, ∞), ℝ);
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A2 γ is a quotient of odd positive integers ak, bk are real constants satisfying bk ≥ ak > 0, k = 1,2, …;
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A3 f ∈ C(ℝ, ℝ), xf(x) > 0 and there exist some positive constants η and α such that f(x)/φα(x) > η for all x ≠ 0 with α ≥ γ.
- (S1)
and ; (S2) and ;
- (S3)
and ; (S4) and , and the cases for k(cj) = k(dj);
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; (2) ; (3) .
Combining (S*) with (*), we can get 12 cases. In order to save space, throughout the paper, we study (1.1) under the case of combination of (S1) with (1) only. The discussions for other cases are similar and omitted.
The following preparatory lemmas will be useful to prove our theorems. The first is derived from [20] and the second from [21].
Lemma 2.1. Let λ and δ be positive real numbers with λ > δ. Then
Lemma 2.2. Suppose X and Y are nonnegative, then
Lemma 2.3. Assume that for any T ≥ t0, there exists cj, dj ∉ {τk}, j = 1, 2, such that T < c1 < d1 ≤ c2 < d2 and
Proof. Without loss of generality, we assume that x(t) > 0 and x(t − σ) > 0 for t ≥ t0. In this case the selected interval of t is [c1, d1]. From (1.1) and (2.7), we obtain
Case (a) (if τi + σ < t ≤ τi+1, then (t − σ, t)⊂(τi, τi+1]). Thus there is no impulsive moment in (t − σ, t). For any s ∈ (t − σ, t), we have
Case (b) (if τi < t < τi + σ, then τi − σ < t − σ < τi < t < τi + σ). There is an impulsive moment τi in (t − σ, t). For any t ∈ (τi, τi + σ), we have
Case (c) (). Since , then . So, there is no impulsive moment in (t − σ, t). Similar to (2.14) of Case (a), we have
Case (d) (). Since , then . Hence, there is an impulsive moment in (t − σ, t). Making a similar analysis of Case (b), we obtain
When x(t) < 0, we can choose interval [c2, d2] to study (1.1). The proof is similar and will be omitted. Therefore we complete the proof.
Theorem 2.4. Assume that for any T ≥ t0, there exists cj, dj ∉ {τk}, j = 1,2, such that T < c1 < d1 ≤ c2 < d2 and (2.7) holds. If there exists wj(t) ∈ Ωj(cj, dj) (j = 1,2) such that, for k(cj) < k(dj),
Proof. Assume, to the contrary, that x(t) is a nonoscillatory solution of (1.1). Without loss of generality, we assume that x(t) > 0 and x(t − σ) > 0 for t ≥ t0. In this case the interval of t selected for the following discussion is [c1, d1].
We define
Differentiating u(t) and in view of (1.1) we obtain, for t ≠ tk,
First, we consider the case k(c1) < k(d1).
In this case, we assume impulsive moments in [c1, d1] are . Choosing a w1(t) ∈ Ω1(c1, d1), multiplying both sides of (2.31) by and then integrating it from c1 to d1, we obtain
Next we consider the case k(c1) = k(d1). By the condition (1) we know there is no impulsive moment in [c1, d1]. Multiplying both sides of (2.31) by and integrating it from c1 to d1, we obtain
When x(t) < 0, we can choose interval [c2, d2] to study (1.1). The proof is similar and will be omitted. Therefore we complete the proof.
Remark 2.5. When γ = 1, p(t) = 0, f(x) = |x|α−1x and the delay term σ = 0, (1.1) reduces to that studied by Liu and Xu [13]. Therefore our Theorem 2.4 generalizes Theorem 2.1 of [13].
Remark 2.6. When γ = α = 1, r(t) = 1 and p(t) = 0, (1.1) reduces to the (1.3) studied by Huang and Feng [16]. Therefore our Theorem 2.4 extends Theorem 2.1 of [16].
Remark 2.7. When ak = bk = 1, for all k = 1,2, …, the impulses in (1.1) disappear, Theorem 2.4 reduces to the main results of [17, 18].
In the following we will establish a Kemenev type interval oscillation criteria for (1.1) by the ideas of Philos [19] and Kong [22].
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A4 H1(t, t) = H2(t, t) = 0, H1(t, s) > 0, H2(t, s) > 0 for t > s;
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A5 (∂/∂t)H1(t, s) = h1(t, s)H1(t, s), (∂/∂s)H2(t, s) = h2(t, s)H2(t, s).
- (S1)
k(cj) < k(δj) < k(dj); (S2) k(cj) = k(δj) < k(dj);
- (S3)
k(cj) < k(δj) = k(dj); (S4) k(cj) = k(δj) = k(dj).
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; (2) .
In the following theorem, we only consider the case of combination of (S1) with (1). For the other cases, similar conclusions can be given and their proofs will be omitted here.
Theorem 2.8. Assume that for any T ≥ t0, there exists cj, dj ∉ {τk}, j = 1,2, such that T < c1 < d1 ≤ c2 < d2 and if there exists a pair of (H1, H2) ∈ ℋ such that
Proof. Assume, to the contrary, that x(t) is a nonoscillatory solution of (1.1). Without loss of generality, we assume that x(t) > 0 and x(t − σ) > 0 for t ≥ t0. In this case the interval of t selected for the following discussion is [c1, d1]. Using the same proof as in Theorem 2.4, we can get (2.31). Multiplying both sides of (2.31) by H1(t, c1) and integrating it from c1 to δ1, we have
On the other hand, similar to (2.43), we have
When x(t) < 0, we can choose interval [c2, d2] to study (1.1). The proof is similar and will be omitted. Therefore we complete the proof.
Remark 2.9. Let H1(t, s) = H2(t, s) = H(t, s), and , the conditions (A4), (A5) can be changed into
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A6 H(t, t) = 0, H(t, s) > 0, for t > s;
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A7 , .
3. Examples
In this section, we give two examples to illustrate the effectiveness and nonemptiness of our results.
Example 3.1. Consider the following equation
For any T > 0, we can choose large n0 ∈ ℕ such that
Let w(t) = sin 12t. It is easy to get that . In view of as k(c1) + 1 > k(d1) − 1, by a simple calculation, the left side of (2.27) is the following
Example 3.2. Consider the following equation
Because M1 = M2 = 1, and , it is easy to get that the right side of the inequality (2.52) for j = 1 is
Acknowledgments
The authors thank the anonymous reviewers for their detailed and insightful comments and suggestions for improvement of paper. This work was supported by the NNSF of China (11161018), and the NSF of Guangdong Province (10452408801004217).