Solutions for p-Laplacian Dynamic Delay Differential Equations on Time Scales
Abstract
Let T be a time scale. We study the existence of positive solutions for the nonlinear four-point singular boundary value problem with p-Laplacian dynamic delay differential equations on time scales, subject to some boundary conditions. By using the fixed-point index theory, the existence of positive solution and many positive solutions for nonlinear four-point singular boundary value problem with p-Laplacian operator is obtained.
1. Introduction
The study of dynamic equations on time scales goes back to its founder Hilger [1] and is a new area of still fairly theoretical exploration in mathematics. Boundary value problems for delay differential equations arise in a variety of areas of applied mathematics, physics, and variational problems of control theory (see [2, 3]). In recent years, many authors have begun to pay attention to the study of boundary-value problems or with p-Laplacian equations or with p-Laplacian dynamic equations on time scales (see [4–14] and the references therein).
In [5], Kaufmann studied the problem (1.3) and obtained the existence results of at least two positives solutions.
However, there are not many concerning the p-Laplacian problems on time scales. Especially, for the singular multipoint boundary value problems for p-Laplacian dynamic delay differential equations on time scales, with the author’s acknowledge, no one has studied the existence of positive solutions in this case.
In this paper, by constructing one integral equation which is equivalent to the problem (1.8), (1.9) and (1.8), and (1.10), we research the existence of positive solutions for nonlinear singular boundary value problem (1.8), (1.9) and (1.8), and (1.10) when g and f satisfy some suitable conditions.
Our main tool of this paper is the following fixed point index theory.
Theorem 1.1 (see [17], [18].)Suppose that E is a real Banach space, K ⊂ E is a cone, let Ωr = {u ∈ K : ∥u∥ ≤ r}. Let operator T:Ωr → K be completely continuous and satisfy Tx ≠ x, ∀ x ∈ ∂Ωr. Then
- (i)
if ∥Tx∥ ≤ ∥x∥, ∀ x ∈ ∂Ωr, then i(T, Ωr, K) = 1;
- (ii)
if ∥Tx∥ ≥ ∥x∥, ∀ x ∈ ∂Ωr, then i(T, Ωr, K) = 0.
This paper is organized as follows. In Section 2, we present some preliminaries and lemmas that will be used to prove our main results. In Section 3, we discuss the existence of single solution of the systems (1.8) and (1.9). In Section 4, we study the existence of at least two solutions of the systems (1.8) and (1.9). In Section 5, we discuss the existence of single and many solutions of the systems (1.8) and (1.10). In Section 6, we give two examples as the application.
2. Preliminaries and Lemmas
For convenience, we can found some basic definitions in [1, 19, 20].
Definition 2.1. u(t) is called a solution of SBVP (1.8) and (1.9) if it satisfies the following:
- (1)
u ∈ C[−τ, 0]∩Cld(0, T),
- (2)
u(t) > 0 for all t ∈ (0, T) and satisfies conditions (1.9),
- (3)
holds for t ∈ (0, T).
-
(H1) f ∈ Cld([0, +∞) 2, [0, +∞)),
-
(H2) g(t) ∈ Cld((0, T), [0, +∞)) and there exists t0 ∈ (0, T), such that
(2.2) -
(H3) ζ(t) ∈ C([−τ, 0], ζ(t) > 0 on [−τ, 0) and ζ(0) = 0,
-
(H4) B0, B1 are both increasing, continuous, odd functions defined on (−∞, +∞), and at least one of them satisfies the condition that there exists one b > 0 such that
(2.3)
Lemma 2.2. Suppose that condition (H2) holds. Then there exists a constant θ ∈ (0, 1/2) that satisfies
Proof. At first, it is easily seen that A(t) is continuous on [θ, T − θ]. Nest, let
Lemma 2.4. Suppose that conditions (H1), (H2), (H3), and (H4) hold, u(t) ∈ B∩Cld(0,1) is a solution of the following boundary value problems:
So in the rest section of this paper, we focus on SBVP (2.9), (2.10), and (2.9), (2.10′).
Lemma 2.5. Suppose that conditions (H1), (H2), (H3), or (H1), (H2), (H3), (H4), hold, u(t) ∈ B∩Cld(0,1) is a solution of boundary value problems (2.9), (2.10) or (2.9), (2.10′), respectively, if and only if u(t) ∈ B is a solution of the following integral equation, respectively:
Proof. We only proof the first section of the results.
Necessity. Obviously, for t ∈ (−τ, 0), we have u(t) = ζ(t).
If t ∈ (0, T), by the equation of the boundary condition and we have uΔ(ξ) ≥ 0, uΔ(η) ≤ 0, then there exist is a constant σ ∈ [ξ, η]⊂(0, T) such that uΔ(σ) = 0.
Firstly, by integrating the equation of the problems (2.9) on (σ, t), we have
By uΔ(σ) = 0 and condition (2.16), t = η on (2.16), we have
From the definition of and above discussion, we deduce that for each . Moreover, we have the following Lemma.
Lemma 2.6. is completely continuous.
Proof. We only proof the completely continuous of T.
Because
Lemma 2.7. Suppose that conditions (H1), (H2), and (H3) hold, the solution u(t) ∈ K of problem (2.9) and (2.10) satisfy
Proof. Firstly, we can have
3. The Existence of Single Positive Solution to (1.8) and (1.9)
In this section, we present our main results.
Theorem 3.1. Suppose that condition (H1), (H2), and (H3) hold. Assume that f also satisfies
-
(A1): f(u1, u2) ≥ (mr)p−1, for θr ≤ u2 ≤ r, 0 ≤ u1 ≤ H,
-
(A2): f(u1, u2) ≤ (MR)p−1, for 0 ≤ u2 ≤ R, 0 ≤ u1 ≤ H,
Then, the SBVP (2.9), (2.10) has a solution u such that ∥u∥ lies between r and R. Furthermore by Lemma 2.4, is a positive solution to the SBVP (1.8) and (1.9).
Proof of Theorem 3.1. Without loss of generality, we suppose that r < R. For any u ∈ K, by Lemma 2.3, we have
- (i)
If σ ∈ [θ, T − θ], thus for u ∈ ∂Ω1, by (A1) and Lemma 2.4, we have
- (ii)
If σ ∈ (T − θ, T], thus for u ∈ ∂Ω1, by (A1) and Lemma 2.4, we have
- (iii)
If σ ∈ (0, θ), thus for u ∈ ∂Ω1, by (A1) and Lemma 2.4, we have
Therefore, no matter under which condition, we all have
On the other hand, for u ∈ ∂Ω2, we have u(t)≤∥u∥ = R, and by (A2), we know that
Therefore, by (3.8), and (3.11), r < R, we have
Theorem 3.2. Suppose that condition (H1), (H2), and (H3) hold. Assume that f also satisfies
-
(A3): ,
-
(A4): .
Proof of Theorem 3.2. First, by , for , there exists an adequately small positive number ρ, as 0 ≤ u2 ≤ ρ, u2 ≠ 0, u1 ≤ H, we have
Next, by condition (A4), , then for , there exists an appropriately big positive number r ≠ R, as u2 ≥ θr, u1 ≤ H, we have
Theorem 3.3. Suppose that conditions (H1), (H2), (H3) hold. Assume that f also satisfies
-
(A5): ,
-
(A6): .
Proof of Theorem 3.3. First, by condition (A6), , then for , there exists an adequately small positive number r, as 0 ≤ u2 ≤ r, u2 ≠ 0, u1 ≤ H, we have
Next, by condition (A5): , then for , there exists an suitably big positive number ρ ≠ r, as u2 ≥ ρ, u1 ≤ H, we have
4. The Existence of Many Positive Solutions to (1.8) and (1.9)
Next, we will discuss the existence of many positive solutions.
Theorem 4.1. Suppose that conditions (H1), (H2), (H3), and (A2) in Theorem 3.1 hold. Assume that f also satisfies
-
(A7): f0 = +∞,
-
(A8): f∞ = +∞.
Proof of Theorem 4.1. First, by condition (A7), for any N > 2/θL, there exists a constant ρ* ∈ (0, R) such that
Finally, set ΩR = {u ∈ K : ∥u∥<R}, For any u ∈ ∂ΩR, by (A2), Lemma 2.3 and also similar to the latter proof of Theorem 3.1, we can also have
Theorem 4.2. Suppose that conditions (H1), (H2), (H3), and (A1) in Theorem 3.1 hold. Assume that f also satisfies
-
(A9): f0 = 0,
-
(A10): f∞ = 0.
Proof of Theorem 4.2. First, by f0 = 0, for ϵ1 ∈ (0, θ*), there exists a constant ρ* ∈ (0, r) such that
Next, let , and note that f*(x) is monotone increasing with respect to x ≥ 0. Then from f∞ = 0, it is easy to see that
Finally, set Ωr = {u ∈ K : ∥u∥<r}. For any u ∈ ∂Ωr, by (A1), Lemma 2.3 and also similar to the previous proof of Theorem 3.1, we can also have
Similar to Theorem 3.1, we also obtain the following Theorems.
Theorem 4.3. Suppose that conditions (H1), (H2), (H3) and (A2) in Theorem 3.1, (A4) in Theorem 3.2 and (A6) in Theorem 3.3 hold. Then, the SBVP (2.9), (2.10) has at last two solutions u1, u2 such that 0 < ∥u1∥<R < ∥u2∥. Furthermore by Lemma 2.4, , −τ ≤ t ≤ T is a positive solution to the SBVP (1.8), (1.10).
Theorem 4.4. Suppose that conditions (H1), (H2), (H3) and (A1) in Theorem 3.1, (A3) in Theorem 3.2 and (A5) in Theorem 3.3 hold. Then, the SBVP (2.9), (2.10) have at last two solutions u1, u2 such that 0 < ∥u1∥<r < ∥u2∥. Furthermore by Lemma 2.4, , , −τ ≤ t ≤ T is a positive solution to the SBVP (1.8), (1.10).
5. The Existence of Many Positive Solutions to (1.8) and (1.10)
In the following, we will deal with problem (1.8), (1.10), the method is similar to that in Sections 3 and 4, so we omit many proof in this section.
Theorem 5.1. Suppose that condition (H1), (H2), (H3), (H4) hold. Assume that f also satisfies
-
f(u1, u2) ≥ (mr)p−1, for θr ≤ u2 ≤ r, 0 ≤ u1 ≤ H,
-
f(u1, u2) ≤ (MR)p−1, for 0 ≤ u2 ≤ R, 0 ≤ u1 ≤ H,
Theorem 5.2. Suppose that condition (H1), (H2), (H3), (H4) hold. Assume that f also satisfies
-
,
-
.
Theorem 5.3. Suppose that condition (H1), (H2), (H3), (H4) hold. Assume that f also satisfies
-
,
-
.
Theorem 5.4. Suppose that conditions (H1), (H2), (H3), (H4) and in Theorem 5.1 hold. Assume that f also satisfies
-
f0 = +∞,
-
f∞ = +∞.
Theorem 5.5. Suppose that conditions (H1), (H2), (H3), (H4) and in Theorem 5.1 hold. Assume that f also satisfies
-
f0 = 0,
-
f∞ = 0.
Theorem 5.6. Suppose that conditions (H1), (H2), (H3), (H4) and (A2) in Theorem 5.1, (A4) in Theorem 5.2 and in Theorem 3.3 hold. Then, the SBVP (2.9), (2.13) has at least two solutions u1, u2 such that 0 < ∥u1∥<R < ∥u2∥. Furthermore by Lemma 2.4, , −τ ≤ t ≤ T is a positive solution to the SBVP (1.8), (1.10).
Theorem 5.7. Suppose that conditions (H1), (H2), (H3), (H4) and in Theorem 5.1, in Theorem 5.2 and in Theorem 3.3 hold. Then, the SBVP (2.9), (2.13) has at least two solutions u1, u2 such that 0 < ∥u1∥<r < ∥u2∥. Furthermore by Lemma 2.4, , −τ ≤ t ≤ T is a positive solution to the SBVP (1.8), (1.10).
6. Application
In the section, we present two simple examples to explain our result.
Example 6.1. Let T = {1 − (1/2) N}∪{1}, where N denotes the set of all nonnegative integers. Consider the following 3-order singular boundary value problem (SBVP) with p-Laplacian
Next,
For θ = 1/4, it is easy to see by calculating that
Example 6.2. Consider the following 3-order singular boundary value problem (SBVP) with p-Laplacian:
Next,
Acknowledgments
The first the second authors were supported financially by Shandong Province Natural Science Foundation (ZR2009AQ004), NSFC (11026108, 11071141), and the third author was supported by Shandong Province planning Foundation of Social Science (09BJGJ14), and Shandong Province Natural Science Foundation (Z2007A04).