Existence of Solutions for Fractional Impulsive Integrodifferential Equations in Banach Spaces
Abstract
We investigate the existence of solutions for a class of impulsive fractional evolution equations with nonlocal conditions in Banach space by using some fixed point theorems combined with the technique of measure of noncompactness. Our results improve and generalize some known results corresponding to those obtained by others. Finally, two applications are given to illustrate that our results are valuable.
1. Introduction
Fractional differential equations arise in many engineering and scientific disciplines as the mathematical modelling of systems and processes in the fields of physics, chemistry, aerodynamics, electrodynamics of complex medium, and polymer rheology and have been emerging as an important area of investigation in the last few decades; see [1–4]. However, the theory of impulsive fractional evolution equations was still in the initial stages and many aspects of this theory need to be explored.
The theory of impulsive differential equations is a new and important branch of differential equation theory, which has an extensive physical, population dynamics, ecology, chemical, biological systems, and engineering background. Therefore, it has been an object of intensive investigation in recent years; some basic results on impulsive differential equations have been obtained and applications to different areas have been considered by many authors; see [4–8].
The paper is organized as follows. In Section 2, we recall some concepts and facts about the Kuratowski measure of noncompactness and some fixed point theorems. In Section 3, we obtain the existence solutions of problem (4). In Section 4, we give two examples to illustrate our results.
2. Preliminaries
In this section, we briefly recall some definitions and the fixed point theorems which will be used in the sequel. Throughout this paper, let E be a Banach space; we assume that A : D(A) ⊂ E → E is a closed linear operator and −A generates a uniformly bounded C0-semigroup T(t) (t > 0) on a Banach space (E, ‖·‖) and M = supt∈[0,+∞)‖T(t)‖B(E), where B(E) stands for the Banach space of all linear and bounded operators in E.
C(J, E) denote the Banach space of all continuous E-value functions on interval J and PC(J, E) = {u : J → E : u ∈ C(tk−1, tk], E), k = 1,2, …, m, and there exist and , k = 1,2, …, m with . Obviously, PC(J, E) is a Banach space with the supnorm ‖u‖ = supt∈J‖u(t)‖.
Definition 1. The fractional integral of order α > 0 with the lower limit zero for a function u is defined as
Definition 2. The Caputo fractional derivative of order α > 0 with the lower limit zero for a function u is defined as
Remark 3. If u is an abstract function with values in E, then the integrals which appear in Definitions 1 and 2 are taken in Bochner’s sense.
Definition 4. By a mild solution of the initial value problem
The following lemma can be found in [14, 15].
Lemma 5. The operators and have the following properties:
- (i)
For any fixed and are linear and bounded operators; that is, for any u ∈ E,
(12) - (ii)
For every u ∈ E, and are continuous functions from [0, ∞) into E.
- (iii)
The operators and are strongly continuous, which means that, for ∀u ∈ E and 0 ≤ t′ < t′′ ≤ a, one has
(13) - (iv)
If the semigroup T(t) is continuous by operator norm for every t > 0, then and are continuous in (0, +∞) by the operator norm.
Let β(·) denote the Kuratowski measure of noncompactness of the bounded set. For the details of the definition and properties of the measure of noncompactness, see [6].
The following lemmas are to be used in proving our main results.
Lemma 6 (see [16].)Let E be a Banach space, and let D ⊂ C(J, E) be equicontinuous and bounded; then β(D(t)) is continuous on J, and β(D) = maxt∈Jβ(D(t)).
Lemma 7 (see [7].)Let D ⊂ E be bounded. Then there exists a countable set D0 ⊂ D, such that β(D) ≤ 2β(D0).
Lemma 8 (see [17].)Let E be a Banach space, and let D = {un} ⊂ C(I, X) be a bounded and countable set. Then β(D(t)) is the Lebesgue integral on X, and
In the following, we introduce the definition of (γ, ψ, p)-contractive mapping.
Definition 9 (see [18].)Let (E, d) be a metric space with w distance p and f : E → E a given mapping. We say that f is an (γ, ψ, p)-contractive mapping if there exist two functions γ : E × E → [0, ∞) and ψ ∈ Ψ such that
We will show some fixed point theorems about condensing operator and (γ, ψ, p)-contractive mapping, which play a key role in the proof of our main results.
Lemma 10 (see [19].)Let E be a Banach space. Assume that D ⊂ E is a bounded closed and convex set on E, Q : D → D is condensing. Then Q has at least one fixed point in D.
Lemma 11 (see [18].)Let p be a w distance on a complete metric space (E, d) and let f : E → E be an (γ, ψ, p)-contractive mapping. Suppose that the following conditions hold:
- (i)
f is an γ-admissible mapping;
- (ii)
there exists a point x0 ∈ E such that γ(x0, fx0) ≥ 1;
- (iii)
either f is continuous or, for any sequence {xn} in E, if γ(xn, xn+1) ≥ 1 for all and xn → x ∈ E as n → ∞, then γ(xn, x) ≥ 1 for all . Then there exists a point u ∈ E such that fu = u. Moreover, if γ(u, u) ≥ 1, then p(u, u) = 0.
3. Main Results
In this section, we will establish the existence theorems of solutions for the nonlocal problem (4). For convenience, we give some notations.
For B ⊂ C(J, E), let B(t) = {u(t) : u ∈ B} and denote BR = {u ∈ E : ‖u‖ ≤ R}. Let k0 = max{k(t, s):(t, s) ∈ D}, h0 = max{h(t, s):(t, s) ∈ D0}. First of all, let us start by defining what we mean by a solution of problem (4).
Definition 12. A function u ∈ PC(J, E) is said to be a mild solution of problem (4) if u satisfies the equation
- (H1)
There exists a positive constant Ki, (i = 1,2, 3) such that
(17) -
and for pi ∈ C(J × E, E), t ∈ J, u, v ∈ BR, there exists a constant bi, ci > 0 such that
(18) - (H2)
For any R > 0, there exist a Lebesgue-integrable function MR : I → R+ and nondecreasing continuous function Ω : [0, ∞ → (0, ∞) such that
(19) -
for all t ∈ I, (x, y, z) ∈ BR × BR × BR.
- (H3)
g : E → E is a continuous and compact mapping; furthermore, there exists positive number N1, N2 such that ‖g(u) − g(v)‖ ≤ N1 and ‖g(u)‖ ≤ N2 for any u, v ∈ BR.
- (H4)
The functions Ik : E → E are continuous and there exists a constant μ > 0 and ρ > 0 such that
(20) - (H5)
There exist constants Li > 0, (i = 1,2, 3) such that for any bounded and equicontinuous sets Di ⊂ C(J, E), (i = 1,2, 3) and t ∈ J,
(21)
Lemma 13 (see [13].)Let f, g : J × E → E be a continuous function and let −A be the generator of a C0-semigroup (T(t)) (t ≥ 0). If u ∈ PC(J, E) is a mild solution of (4) in the sense of Definition 12, then for any t ∈ (tk−1, tk], k = 1, …, m,
Theorem 14. Let E be a Banach space, let A : D(A) ⊂ E → E be a closed linear operator, and −A generates an equicontinuous C0-semigroup T(t) (t ≥ 0) of uniformly bounded operators in E. Suppose that the conditions (H1)–(H5) are satisfied. Then for every u0 ∈ PC(J, E) there exists a τ1 = τ1(u0), 0 < τ1 < a such that problem (4) has a solution u ∈ PC([0, τ1], E).
Proof. Since we are interested here only in local solutions, we may assume that a < ∞. By using our assumption (H1)–(H4), let t′ > 0, R = M(2‖u0‖ + 1) > 0 be such that BR(u0) = {u : ‖u − u0‖ ≤ R}, for 0 ≤ t ≤ t′ and u ∈ BR(u0), and let us choose
And by (19), we have
Now, we demonstrate that the operator Q : Ω → Ω is equicontinuous. For any u ∈ Ω and 0 ≤ t1 < t2 ≤ τ1, we get that
For I1, by Lemma 5(iii), ‖I1‖ → 0 as t2 − t1 → 0.
For I2, by Lemma 5(iii), we have
For I3, by Lemma 5(i), we have
For I4, by Lemma 5(i), we have
For I5, by Lemma 5(iii), we have
For I6, by Lemma 5(iii), we have
Let . Then it is easy to verify that Q maps B into itself and B ⊂ PC(J, E) is equicontinuous. Now, we prove that Q : B → B is a condensing operator. For any D ⊂ B, by Lemma 7, there exists a countable set D0 = {un} ⊂ D, such that
By the fact that
Thus, by (H1), (H2), (39), and Lemma 13, we have
Corollary 15. Let E be a Banach space. A : D(A) ⊂ E → E be a closed linear operator and −A generates an equicontinuous C0-semigroup T(t) (t ≥ 0) of uniformly bounded operators in E. Suppose that the conditions (H1)–(H5) are satisfied. Then for every u0 ∈ PC(J, E) there exists a τ1 = τ1(u0), 0 < τ1 < a such that the nonlocal problem
Proof. Let the function ; by the similar way one can easily verify the conditions (H1)–(H5) by properly choosing ci. Hence, by Theorem 14, problem (43) has a solution.
Theorem 16. Let ξ : E × E → R+ be a given function. Assume that the following conditions hold:
- (A)
there exists ψ ∈ Ψ such that
(44) -
for all t ∈ J and for all a, b ∈ E with ξ(a, b) ≥ 0;
- (B)
there exists u0 ∈ PC(J, E) such that ξ(u0(t), Qu0(t)) ≥ 0 for all t ∈ J, where a mapping Q : PC(J, E) → PC(J, E) is defined by
(45) - (C)
for each t ∈ J, and u, v ∈ PC(J, E), ξ(u(t), v(t)) ≥ 0 implies that ξ(Qu(t), Qv(t)) ≥ 0;
- (D)
for each t ∈ J, if {un} is a sequence in PC(J, E) such that un → u in PC(J, E) and ξ(un(t), un+1(t)) ≥ 0 for all , then
(46) -
for all
Proof. First of all, let E = PC(J, E). It is easy to see that u ∈ E is a solution of (4) if and only if u ∈ E is a solution of the integral equation
Now, let u, v ∈ E such that ξ(u(t), v(t)) ≥ 0 for all t ∈ J. By condition (A), we have
4. Applications
In this section, we present two examples, which illustrate the applicability of our main results.
Example 1. We consider the following impulsive fractional differential equation:
Example 2. Consider the following impulsive fractional differential equation:
5. Conclusions
In this paper, we studied the existence of solutions for a class of impulsive fractional evolution equations with nonlocal conditions in Banach space by using some fixed point theorems combined with the technique of measure of noncompactness. Our results improve and generalize some known results corresponding to those obtained by others.
Competing Interests
The authors declare that they have no competing interests.
Acknowledgments
This work is supported by the National Natural Science Foundation of China (Grant no. 11061031).