Hindawi Publishing Corporation Advances in Difference Equations Volume 2011, Article ID 690653, 12 pages doi:10.1155/2011/690653 Research Article Existence of Solutions to Fractional Mixed Integrodifferential Equations with Nonlocal Initial Condition A. Anguraj,1 P. Karthikeyan,2 and J. J. Trujillo3 1 Department of Mathematics, PSG College of Arts and Science, Coimbatore 641 014, India Department of Mathematics, KSR College of Arts and Science, Tiruchengode 637 215, India 3 Departamento de Análisis Matemático, Universidad de La Laguna, Tenerife 38271 La Laguna, Spain 2 Correspondence should be addressed to J. J. Trujillo, jtrujill@ullmat.es Received 14 November 2010; Accepted 6 January 2011 Academic Editor: Dumitru Baleanu Copyright q 2011 A. Anguraj et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We study the existence and uniqueness theorem for the nonlinear fractional mixed Volterra-Fredholm integrodifferential equation with nonlocal initial condition dα xt/dtα ft, xt, t 1 1 kt, s, xsds, 0 ht, s, xsds, x0 0 gsxsds, where t ∈ 0, 1, 0 < α < 1, and f is a 0 given function. We point out that such a kind of initial conditions or nonlocal restrictions could play an interesting role in the applications of the mentioned model. The results obtainded are applied to an example. 1. Introduction Recently it have been proved that the differential models involving nonlocal derivatives of fractional order arise in many engineering and scientific disciplines as the mathematical modeling of systems and processes in many fields, for instance, physics, chemistry, aerodynamics, electrodynamics of complex medium, polymer rheology, and so forth see 1– 6. In fact, such models can be considered as an efficient alternative to the classical nonlinear differential models to simulate many complex processes see 7. For instance, fractional differential equations are an excellent tool to describe hereditary properties of viscoelastic materials and, in general, to simulate the dynamics of many processes on anomalous media. Theory of fractional differential equations has been extensively studied by several authors as Delbosco and Rodino 8, Kilbas et al. 6, Lakshmikantham et al. 9–11, and also see 2, 12–16. 2 Advances in Difference Equations Recently Mophou and N’Guérékata 17, studied the Cauchy problem with nonlocal conditions Dq xt Axt tn ft, xt, Bxt, t ∈ 0, T , n ∈ Z , x0 gx x0 , 1.1 in general Banach space X with 0 < q < 1, and A is the infinitesimal generator of a C0 semigroup of bounded linear operators. By means of the Krasnoselskii’s Theorem, existence of solutions was also obtained. Subsequently several authors have investigated the problem for different types of nonlinear differential equations and integrodifferential equations including functional differential equations in Banach spaces. Very recently N’Guérékata 2, 18 discussed the existence of solutions of fractional abstract differential equations with nonlocal initial condition. The nonlocal Cauchy problem is discussed by authors in 15 using the fixed-point concepts. Tidke 19 studied the nonfractional mixed Volterra-Fredholm integrodifferential equations with nonlocal conditions using Leray-Schauder Theorem. Motivated by the above mentioned works in this manuscript we discuss the existence and the uniqueness of the solution for the following fractional integrodifferential equation with nonlocal integral initial condition in Banach Space: dα xt f dtα t t, xt, 1 kt, s, xsds, 0 x0 ht, s, xsds , 0 1.2 1 gsxsds, 0 where t ∈ J 0, 1, 0 < α < 1, gt ∈ 0, 1, g ∈ L1 0, 1, R , x ∈ Y CJ, E is a continuous function on J with values in the Banach space E and xY maxt∈J xtE , and f : J × E × E × E → E, k : D × E → E, and h : D0 × E → E are continuous E-valued functions. Here D {t, s ∈ R2 : 0 ≤ s ≤ t ≤ 1}, and D0 J × J. The operator dα /dtα denotes the Caputo fractional derivative of order α. For the sake of the shortness let Kxt t kt, s, xsds, 0 Hxt 1 ht, s, xsds. A 0 The paper is organized as follows. In Section 2, some definitions, lemmas and preliminary results are introduced to be used in the sequel. Section 3 will involve the assumptions, main results and proofs of existence problem of 1.2, together with a nonlocal initial condition. Finally an example is presented. 2. Preliminaries Let E be a real Banach space and θ the zero element of E. Let L1 0, 1, E be the Banach space of measurable functions x : 0, 1 → E which are Lebesgue integrable, equipped with the Advances in Difference Equations 3 1 norm xL1 0 xsds. We will use the following notation R 0, ∞, and R 0, ∞. A function x ∈ C0, 1, E is called a solution of 1.2 if it satisfies 1.2. Definition 2.1. A real function ft is said to be in the space Cα , α ∈ R if there exists a real number p > α, such that ft tp gt, where g ∈ C0, ∞, while ft is said to be in the space Cαm if and only if f m ∈ Cα , m ∈ N. Definition 2.2. The fractional arbitrary order Riemann-Liouville integral on the right and on the left of the function f ∈ L1 a, b, R of order α, a, b ∈ R is defined by Iaα ft 1 Γα t a t − sα−1 fsds, Γα α Ib− ft 1 Γα b t s − tα−1 fsds, Γα 2.1 where Γ is the Gamma function of Euler. α When a 0, we write I α ft I0 ft f ∗ φα t, where φα t tα−1 /Γα for t > 0, φα t 0 for t ≤ 0, and ∗ represents the Convolution of Laplace. Then, it is well known that φα t → δt as α → 0, where δ is the Delta function. Definition 2.3. The Riemann-Liouville fractional integral operator of order α > 0, of a function f ∈ Cμ , μ ≥ −1 is defined as I α ft φα ∗ ft, α > 0, t > 0, I 0 fx fx. 2.2 Definition 2.4. The Caputo’s derivative of fractional order α > 0 for a suitable function ft is defined by c 1 D f t Γn − α α t 0 f n s t − sα−n1 ds, n − 1 < α < n, n α 1, 2.3 where α denotes the integer part of real number α. It is obvious that the Caputo’s derivative of a constant is equal to 0. Lemma 2.5. Let α > 0 and n α 1. Then n−1 k f 0 k t . I α c Dα f t ft − k! k0 2.4 1 α Lemma 2.6. If Qτ, α ΓαI1− gτ τ gss − τα−1 ds for τ ∈ 0, 1, and if g ∈ L1 0, 1, R satisfies 0 ≤ gs ≤ 1 for 0 ≤ s ≤ 1 and α > 0, then Qτ, α < e, Γα t 0 t − sα−1 ds < e. Γα 2.5 4 Advances in Difference Equations Proof. A direct computation shows Qτ, α Γα 1 τ 1 gss − τα−1 ds s − τα−1 ds ∞ τ ∞ sα−1 e−s ds sα−1 e−s ds 0 0 1−τ t 0 sα−1 ds ∞0 sα−1 e−s ds 0 t e 1−τ ≤ 0∞ 0 sα−1 e−s ds sα−1 e−s ds < e, 2.6 t sα−1 ds e sα−1 e−s ds t − sα−1 ds ∞0 ≤ ∞0 < e. Γα sα−1 e−s ds sα−1 e−s ds 0 0 Theorem 2.7 Krasnoselkii. Let X be a Banach space, let S be a bounded closed convex subset of X and let A, B be maps of S into X such that Ax By ∈ S for every pair x, y ∈ S. If A is completely continuous and B is a contraction then the equation Ax Bx x has a solution on S. 3. Main Results We assume the following. A1 If f ∈ C0, 1 × E × E × E, E and a nonnegative, bounded pf ∈ L1 0, 1, R , there exist M > 0, pf t ≤ M for t ∈ 0, 1 such that ft, x, Kx, Hx ≤ pf tx for x ∈ E. 3.1 A2 There exist positive constants L1 , L2 , and L such that f t, x1 , y1 , z1 − f t, x2 , y2 , z2 ≤ L1 x1 − x2 y1 − y2 z1 − z2 3.2 for all x1 , y1 , z1 , x2 , y2 , z2 ∈ Y , L2 maxt∈J ft, 0, 0, 0, and L max{L1 , L2 }. A3 There exist positive constants N1 , N2 , and N such that kt, s, x1 − kt, s, x2 ≤ N1 x1 − x2 3.3 for all x1 , x2 ∈ Y , N2 maxt,s∈D kt, s, 0, and N max{N1 , N2 }. A4 There exist positive constants C1 , C2 , and C such that ht, s, x1 − ht, s, x2 < C1 x1 − x2 3.4 for all x1 , x2 ∈ Y , C2 maxt,s∈D0 ht, s, 0, and C max{C1 , C2 }. A5 p L/Γα 11 C N/α 1 is such that 0 ≤ p < 1. Firstly, we obtain the following lemmas to prove the main results on the existence of solutions to 1.2. Advances in Difference Equations 5 1 Lemma 3.1. If (A1) holds with μ 0 gsds, then the problem 1.2 is equivalent to the following equation: 1 1 Qτ, αfτ, xτ, Kxτ, Hxτdτ φα t ∗ ft, xt, Kxt, Hxt. xt 1 − μ Γα 0 3.5 Proof. By Lemma 2.5 and 1.2, we have 1 xt x0 Γα t 3.6 t − sα−1 fs, xs, Kxs, Hxsds. 0 Therefore, x0 1 gsxsds 0 1 0 1 gsdsx0 Γα 1 s gs 0 3.7 s − τα−1 fτ, xτ, Kxτ, Hxτdτ ds. 0 So, 1 x0 1 − μ Γα 1 1 − μ Γα 1 1 fτ, xτ, Kxτ, Hxτ 0 s − τ τ 1 α−1 gsds dτ 3.8 Qτ, αfτ, xτ, Kxτ, Hxτdτ, 0 and then 1 xt 1 − μ Γα 1 Qτ, αfτ, xτ, Kxτ, Hxτdτ φα t ∗ ft, xt, Kxt, Hxt. 0 3.9 Conversely, if x is a solution of 3.5, then for every t ∈ 0, 1, according to Definition 2.4 we have 1 1 c α c α Qτ, αfτ, xτ, Kxτ, Hxτdτ D xt D 1 − μ Γα 0 φα t ∗ ft, xt, Kxt, Hxt 3.10 θ c Dα I α ft, xt, Kxt, Hxt ft, xt, Kxt, Hxt. It is obvious that x0 1 0 gsxsds. This completes the proof. 6 Advances in Difference Equations Lemma 3.2. If (A3) and (A4) are satisfied, K, H are defined in A, then the conditions Kxt ≤ tN1 x N2 , Kx1 t − Kx2 t ≤ N1 tx1 − x2 , Hxt ≤ C1 x C2 , 3.11 Hx1 t − Hx2 t ≤ C1 x1 − x2 , are satisfied for any t ∈ J, and x, x1 , x2 ∈ Y . Proof. By A3, we have Kxt ≤ t kt, s, xsds 0 t kt, s, xs − kt, s, 0 kt, s, 0ds 0 ≤ t kt, s, xs − kt, s, 0ds 0 t 3.12 kt, s, 0ds 0 ≤ N1 tx N2 t ≤ N1 x N2 . On the other hand, Kx1 t − Kx2 t ≤ t kt, s, x1 s − kt, s, x2 sds 0 ≤ N1 t x1 s − x2 sds 3.13 0 ≤ N1 tx1 − x2 . Similarly, for the other conditions, we use assumption A4, to get Hxt ≤ 1 ht, s, xsds ≤ C1 x C2 , 0 3.14 Kx1 t − Kx2 t ≤ C1 x1 − x2 . Theorem 3.3. If (A1)–(A5) are satisfied, then the fractional integrodifferential equation 1.2 has a unique solution continuous in J. Proof. We use the Banach contraction principle to prove the existence and uniqueness of the solution to 1.2. Let Br {x ∈ Y : x ≤ r} ⊆ Y , where r ≥ eM/1 − μ L/Γα 11 C N/α 1 and define the operator Ψ on the Banach space Y by 1 1 Qτ, αfτ, xτ, Kxτ, Hxτdτ 1 − μ Γα 0 t 1 t − sα−1 fs, xs, Kxs, Hxsds. Γα 0 Ψxt 3.15 Advances in Difference Equations 7 Firstly, we show that the operator Ψ maps Br into itself. By using A1 and triangle inequality, we have t 1 eM α−1 x Ψxt ≤ t − s fs, xs, Kxs, Hxsds 1−μ Γα 0 t eM 1 ≤ x t − sα−1 fs, xs, Kxs, Hxsds 1−μ Γα 0 eM x 1−μ t 1 t − sα−1 fs, xs, Kxs, Hxs − fs, 0, 0, 0 fs, 0, 0, 0ds Γα 0 t eM 1 ≤ x t − sα−1 fs, xs, Kxs, Hxs − fs, 0, 0, 0ds 1−μ Γα 0 t 1 t − sα−1 fs, 0, 0, 0ds. Γα 0 3.16 ≤ Now, if A2 is satisfied, then L1 t eM x t − sα−1 xs Kxs Hxsds 1−μ Γα 0 L2 t t − sα−1 ds Γα 0 L1 t eM L1 t x ≤ t − sα−1 xsds t − sα−1 Kxsds 1−μ Γα 0 Γα 0 L1 t L2 t t − sα−1 Hxsds t − sα−1 ds. Γα 0 Γα 0 Ψxt ≤ 3.17 Using Lemma 3.2 and A3, we have Ψxt ≤ eM L1 L1 x tα x N1 x N2 1−μ Γα 1 Γα ≤ t L2 L1 tα C1 x C2 tα Γα 1 Γα 1 L1 eM L1 x tα x tα1 N1 x N2 1−μ Γα 1 Γα 2 L2 L1 tα C1 x C2 tα Γα 1 Γα 1 t − sα−1 sds 0 L1 N2 α1 eM L1 C2 α L2 x t t tα 1−μ Γα 2 Γα 1 Γα 1 L1 N1 α t 1 t C1 x, Γα 1 α1 3.18 8 Advances in Difference Equations if x ∈ Br , we have eM L N x 1 C 1−μ Γα 1 α1 Lr N 1 C Γα 1 α1 ≤ r. Ψxt ≤ 3.19 Thus ΨBr ⊂ Br . Next, we prove that Ψ is a contraction mapping. For this, let x1 , x2 ∈ Y . Applying A2, we have Ψx1 t − Ψx2 t Qτ, α 1 fs, x1 τ, Kx1 τ, Hx1 τ − fs, x2 τ, Kx2 τ, Hx2 τ dτ 1 − μ Γα 0 t 1 t − sα−1 fs, x1 s, Kx1 s, Hx1 sds Γα 0 t 1 α−1 − t − s fs, x2 s, Kx2 s, Hx2 sds Γα 0 1 e ≤ L1 x1 τ − x2 τ Kx1 τ − Kx2 τ Hx1 τ − Hx2 τdτ 1−μ 0 t L1 t − sα−1 x1 s − x2 sds Γα 0 t t α−1 α−1 t − s Kx1 s − Kx2 sds t − s Hx1 s − Hx2 sds 0 0 3.20 then using A3, A4 and Lemma 3.2, one gets Ψx1 t − Ψx2 t 1 1 1 L1 e dτ N1 τdτ C1 dτ ≤ x1 − x2 1−μ 0 0 0 t t t L1 α−1 α−1 α−1 x1 − x2 t − s ds N1 t − s sds C1 t − s ds Γα 0 0 0 α α1 t N1 Γαt C1 tα L1 N1 L1 e C1 x1 − x2 x1 − x2 ≤ 1 2 Γα α Γα 2 α 1−μ 3.21 L1 e N1 L1 N1 α C1 1 C1 1 t t x1 − x2 2 Γα 1 α1 1−μ N L N Le x1 − x2 C1 1C ≤ 1 2 Γα 1 α1 1−μ N Le C p x1 − x2 ≤ 1 2 1−μ ≤ ΩC,N,α,μ,p x1 − x2 , Advances in Difference Equations 9 where ΩC,N,α,μ,p Le/1 − μ1 N/2 C p < 1 depends on the parameter of the problem. Therefore Ψ has a unique fixed-point x Ψx ∈ Br , which is a solution of 3.5, and hence is a solution of 1.2. Theorem 3.4. Assume (A1)–(A4) holds. If eM < 1 − μ, then 1.2 has at least one solution on I. Proof. Choose r ≥ eM/1 − μ pf L1 /Γα 1 and consider Br : {x ∈ C : x ≤ r}. Now define on Br the operators A, B by Axt : φα t ∗ ft, xt, Kxt, Hxt, 1 1 Qτ, αfτ, xτ, Kxτ, Hxτdτ. Bxt : 1 − μ Γα 0 3.22 Let us observe that if x, y ∈ Br then Ax By ∈ Br . Indeed it is easy to check the inequality pf 1 eM L Ax By ≤ ≤ r. Γα 1 1−μ 3.23 We can easily show that that B is a contraction mapping. Let u, v ∈ Br . Then But − Bvt 1 1 − μ Γα : e ≤ 1−μ 1 1 Qτ, αfτ, uτ, Kuτ, Huτ − fτ, vτ, Kvτ, Hvτdτ 0 L1 uτ − vτ Kuτ − Kvτ Huτ − Hvτdτ 0 L1 e N1 C1 u − v 1 2 1−μ ≤ ≤ ΛN1 ,C1 ,L1 u − v, 3.24 where ΛN1 ,C1 ,L1 L1 e/1 − μ1 N1 /2 C1 < 1 depends only on the parameter of the problem and hence B is contraction. Since x is continuous, then Axt is continuous in view of A1. Let us now note that A is uniformly bounded on Br . This follows from the inequality Axt ≤ pf 1 L Γα 1 Now let us prove that Axt is equicontinuous. . 3.25 10 Advances in Difference Equations Let t1 , t2 ∈ J and x ∈ Br . Using the fact that f is bounded on the compact set J ×Br thus supt,s∈J×Br ft, xs, Kxs, Hxs : c0 < ∞, we will get s t 1 1 Axt1 − Axt2 t1 − sq−1 fs, xs, Kxs, Hxsds Γ q 0 0 − t2 t2 − s q−1 s 0 0 fs, xs, Kxs, Hxsds s t 1 1 q−1 t1 − s fs, xs, Kxs, Hxsds Γ q t2 0 − t2 t2 − s q−1 q−1 − t1 − s s 0 0 1 ≤ Γ q fs, xs, Kxs, Hxsds t s 1 q−1 fs, xs, Kxs, Hxsds t1 − s t2 0 1 Γ q t s 2 q−1 q−1 fs, xs, Kxs, Hxsds t2 − s − t1 − s 0 0 c0 q q ≤ 2t1 − t2 q t2 − t1 Γ q1 2c0 ≤ |t1 − t2 |q , Γ q1 3.26 which does not depend on x. So ABr is relatively compact. By the Arzela-Ascoli Theorem, A is compact. We now conclude the result of the theorem based on the Krasnoselkii’s theorem above. 4. Example Consider the following fractional integrodifferential equation: c Dα xt e−t xt 1 t 9 e 1 xt 10 t e−1/2xs ds 0 x0 1 0 1 10 1 xsds, 2 t 0 e−1/49xs ds, t ∈ J 0, 1, 4.1 Advances in Difference Equations 11 t t where 0 < α ≤ 1. Take E R . Set Kxt 0 e−1/2xs ds, Hxt 0 e−1/49xs ds, ft, x, Kx, Hx e−t x/9 et 1 x Kx Hx, gs 1/2, pf t e−t xt/9 et . Then it is clear that f ∈ C0, 1 × E × E × E, E, pf ∈ L0, 1, R , pf t ≤ 1 M, 10 4.2 ft, x, Kx, Hx ≤ pf x. So, A1 is satisfied. Let x, y ∈ E and t ∈ J. Then we have t 1 t −1/2xs −1/2ys Kx − Ky e ds − e ds ≤ x − y, 0 2 0 t t −1/49xs 1 −1/49ys Hx − Hy e x − y, ds − e ds ≤ 0 49 0 ft, x, Kx, Hx − f t, y, y, Hy e−t y e−t x 1 − Kx − Ky Hx − Hy 9 et 1 x 9 et 1 y 10 e−t x − y 1 ≤ Kx − Ky Hx − Hy t 10 9 e 1 x 1 y 4.3 1 e−t x − y Kx − Ky Hx − Hy t 10 9e 1 x − y Kx − Ky Hx − Hy . ≤ 10 ≤ Hence the conditions A1–A4 hold with M 1/10, L1 1/10, N1 1/2, C1 1/49. Choose r 1 and μ 1/2. 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