International Journal of Analysis and Applications ISSN 2291-8639 Volume 12, Number 2 (2016), 80-86 http://www.etamaths.com ON EXISTENCE OF SOLUTIONS TO THE CAPUTO TYPE FRACTIONAL ORDER THREE-POINT BOUNDARY VALUE PROBLEMS B.M.B. KRUSHNA1,∗ AND K.R. PRASAD2 Abstract. In this paper, we establish the existence of solutions to the fractional order three-point boundary value problems by utilizing Banach contraction principle and Schaefer’s fixed point theo- rem. 1. Introduction Fractional calculus deals with integration and differentiation of an arbitrary real order. Fractional order derivatives provide a new approach for modeling complex phenomena in physics, mechanics, control systems, flow in porous media, signal and image processing, aerodynamics, electromagnetics, viscoelasticity and especially dealing with memory and hereditary properties of various real materials [5, 6, 9, 11]. Compared to integer order models, the fractional order models offer better description of underlying processes. In consequence, fractional order differential equations have achieved great deal of interest and attention of researchers [1, 2, 4, 7, 10, 12, 13, 14, 16, 17, 18]. Zhang [20] obtained the existence and uniqueness of solutions for two-point fractional order bound- ary value problem Dα0+u(t) = f ( t,u(t) ) , t ∈ (0, 1), u(0) + u′(0) = 0, u(1) + u′(1) = 0, where Dα 0+ is the Caputo fractional order derivative and 1 < α ≤ 2. Shi and Zhang [17] given sufficient conditions for the existence of at least one solution for fractional order boundary value problem Dδu(t) + g(t,u) = 0, t ∈ (0, 1), u(0) = a, u(1) = b, where 1 < δ ≤ 2, g : [0, 1] ×R → R and Dδ is the Caputo fractional order derivative, using upper and lower solutions method. Benchohra, Hamani and Ntouyas [3] derived sufficient conditions for the existence of at least one solution to the fractional order boundary value problem CDαu(t) = f ( t,u(t) ) , 0 < t < T, u(0) = g(u), u(T) = uT , where 1 < α ≤ 2, CDα is the Caputo fractional order derivative, by using Schaefer’s fixed point theorem. Also they established criteria for the uniqueness of solutions by virtue of the Banach fixed point theorem. In [8], the authors studied the existence and uniqueness of solutions to the boundary value problem Dαu(t) = f(t,u(t),u′(t)), t ∈ (0, 1), u(0) = 0, Dpu(1) = δDpu(η), 2010 Mathematics Subject Classification. 26A33, 34A08, 34B15. Key words and phrases. fractional order derivative; boundary value problem; solution. c©2016 Authors retain the copyrights of their papers, and all open access articles are distributed under the terms of the Creative Commons Attribution License. 80 EXISTENCE OF SOLUTIONS TO THE CAPUTO TYPE FBVPS 81 where D is the Caputo fractional order derivative, 1 < α ≤ 2, 0 < δ < p < 1, 0 < η ≤ 1, by using some fixed point theorem. In this paper we consider the fractional order three-point boundary value problem (1.1) CDqy(t) = f ( t,y(t) ) , t ∈ (0, 1), (1.2)   y(0) + y′(0) + y′′(0) =0, y(η) + y′(η) + y′′(η) =0, y(1) + y′(1) + y′′(1) =0, where q ∈ (2, 3],η ∈ (0, 1) and CDq is the standard Caputo fractional order derivative. We assume that the following conditions hold throughout the paper: (A1) f : [0, 1] ×R → R is continuous, (A2) there exists a positive constant M such that ∣∣f(t,y)∣∣ ≤M, for each t ∈ [0, 1] and y ∈ R, (A3) there exists a positive real constant ξ such that |f(t,y) −f(t,y)| ≤ ξ|y −y| for each t ∈ [0, 1], for all y, y ∈ R. 1.1. Preliminaries. In this section, we present some definitions and lemmas that are useful in the proof of our main results. Definition 1.1. [11] The Riemann–Liouville fractional integral of order p > 0 of a function f : [0, +∞) → R is given by I p 0+ f(t) = 1 Γ(p) ∫ t 0 (t− τ)p−1f(τ)dτ, provided the right-hand side is defined. Definition 1.2. [11] The Caputo fractional derivative of order α > 0 of a function f : [a, +∞) → R is given by C a D α t f(t) = 1 Γ(α−n) ∫ t a f(n)(τ) (t− τ)α+1−n dτ, (n− 1 < α < n), provided the right-hand side is defined. Lemma 1.1. [11] Let α > 0, then the fractional order differential equation CDαu(t) = 0 has solution, u(t) = c0 + c1t + c2t 2 + · · · + cn−1tn−1, ci ∈ R, i = 0, 1, 2, · · ·,n− 1, n = [α] + 1. Lemma 1.2. [11] Let α > 0, then Iα CDαu(t) = u(t) + c0 + c1t + c2t 2 + · · ·+ cn−1tn−1 for ci ∈ R, i = 0, 1, 2, · · ·,n− 1, n = [α] + 1. The rest of the paper is organized as follows. In Section 2, we establish the conditions for the existence of solutions to the fractional order boundary value problem (1.1)-(1.2) by using different fixed point theorems such as Banach contraction principle and Schaefer’s fixed point theorem. In Section 3, we present examples to illustrate the applicability of the conditions. 2. Main results In this section, by stating some lemmas, we establish sufficient conditions for the existence of solu- tions to the fractional order boundary value problem (1.1)-(1.2) using certain fixed point theorems. Let B = Cq ( [0, 1],R ) be the Banach space of all continuous functions from [0, 1] into R equipped with the norm ‖y‖ = max t∈[0,1] ∣∣y(t)∣∣. 82 KRUSHNA AND PRASAD Lemma 2.1. Let ∆ = (η2 − η)Γ(q) 6= 0. Assume that condition (A1) is satisfied. A function y ∈ Cq ( [0, 1],R ) is a solution of the fractional integral equation (2.1)   y(t) = ∫ t 0 (t−s)q−1 Γ(q) f ( s,y(s) ) ds + [ t2 − 3t + 1 ∆ ] × ∫ η 0 Φ(s)f ( s,y(s) ) ds + [ η2(t− 1) + ηt(2 − t) ∆ ] × ∫ 1 0 Ψ∗(s)f ( s,y(s) ) ds, where (2.2) { Φ(s) =(η −s)q−1 + (q − 1)(η −s)q−2 + ( q2 − 3q + 2 ) (η −s)q−3, Ψ∗(s) =(1 −s)q−1 + (q − 1)(1 −s)q−2 + ( q2 − 3q + 2 ) (1 −s)q−3, if and only if y is a solution of the fractional order boundary value problem (1.1)-(1.2). Proof. Let y(t) ∈ Cq[0, 1] be the solution of fractional order boundary value problem (1.1)-(1.2). An equivalent integral equation for (1.1) and is given by (2.3) y(t) = ∫ t 0 (t−s)q−1 Γ(q) f(s,y(s))ds + k1 + k2t + k3t 2. Using the conditions (1.2) to y(t) in (2.3) and by algebraic calculations, we can get k1 = 1 ∆ [∫ η 0 Φ(s)f ( s,y(s) ) ds−η2 ∫ 1 0 Ψ∗(s)f ( s,y(s) ) ds ] k2 = 1 ∆ [ (η2 + 2η) ∫ 1 0 Ψ∗(s)f ( s,y(s) ) ds− 3 ∫ 1 0 Φ(s)f ( s,y(s) ) ds ] k3 = 1 ∆ [∫ η 0 Φ(s)f ( s,y(s) ) ds−η ∫ 1 0 Ψ∗(s)f ( s,y(s) ) ds ] . By substituting the values of k1,k2,k3 in (2.3), we obtain (2.1). This completes the proof. � Now we establish the existence of solution to the fractional order boundary value problem (1.1)-(1.2) by an application of Banach contraction principle [15]. Lemma 2.2. (Banach contraction principle) Let (X,d) be a complete metric space. Let T : X → X be a contraction. That is, there exists λ ∈ [0, 1) such that d(Tx,Ty) ≤ λd(x,y), for all x,y ∈ X. Then there exists a unique fixed point of T. Theorem 2.3. Assume that the conditions (A1) and (A3) are satisfied. If (2.4) ζ = ∣∣∣∣ξ(η + 1)(ηq−2 + 1)Γ(q + 1)(η − 1) ∣∣∣∣ < 1, then the fractional order boundary value problem (1.1)-(1.2) has a solution on [0, 1]. Proof. We transform the fractional order boundary value problem (1.1)-(1.2) in to a fixed point problem by defining an operator T. Let T : B →B be the operator defined by (2.5)   Ty(t) = ∫ t 0 (t−s)q−1 Γ(q) f ( s,y(s) ) ds− [t2 − 3t + 1 ∆ ] × ∫ η 0 Φ(s)f ( s,y(s) ) ds − [η2(t− 1) + η(2 − t)t ∆ ] × ∫ 1 0 Ψ∗(s)f ( s,y(s) ) ds. Clearly the fixed points of the operator T are the solutions of the fractional order boundary value problem (1.1)-(1.2). Now we show that the operator T is a contraction mapping. Let y, y ∈ B and EXISTENCE OF SOLUTIONS TO THE CAPUTO TYPE FBVPS 83 using (2.2), then for each t ∈ [0, 1], we have ∣∣Ty(t) −Ty(t)∣∣ ≤∫ t 0 (t−s)q−1 Γ(q) ∣∣∣f(s,y(s))−f(s,y(s))∣∣∣ds + ∣∣∣∣t2 − 3t + 1∆ ∣∣∣∣× ∫ η 0 Φ(s) ∣∣∣f(s,y(s))−f(s,y(s))∣∣∣ds + ∣∣∣∣η2(1 − t) + η(t− 2)t∆ ∣∣∣∣× ∫ 1 0 Ψ∗(s) ∣∣∣f(s,y(s))−f(s,y(s))∣∣∣ds ≤ { (t−s)q qΓ(q) + 1 |∆| × ∫ η 0 Φ(s)ds + ∣∣∣ η ∆ ∣∣∣×∫ 1 0 Ψ∗(s)ds }[ ξ‖y −y‖∞ ] ≤ ∣∣∣∣ξ(ηq−2 + 1)(η + 1)(η − 1)Γ(q + 1) ∣∣∣∣∥∥y −y∥∥∞. Hence ‖Ty(t)−Ty(t)‖∞ ≤ ζ‖y−y‖. Therefore T is a contraction mapping. By the contraction mapping principle, the operator T has a fixed point and is the solution of the fractional order boundary value problem (1.1)-(1.2). � Next we establish the result by applying Schaefer’s fixed point theorem [19]. Lemma 2.4. (Schaefer′s fixed point theorem) Let F : X → X be a completely continuous op- erator. If the set E(F) = { x ∈ X : x = λ∗Fx, for some λ∗ ∈ [0, 1] } is bounded. Then F has fixed points. Theorem 2.5. Assume that the conditions (A1)-(A2) are satisfied. Then the fractional order boundary value problem (1.1)-(1.2) has at least one solution on [0, 1]. Proof. We prove that the operator T is defined by (2.5) has a fixed point by utilizing Schaefer’s fixed point theorem. Now we establish the result in 4 steps. Step 1. The operator T given by (2.5) is continuous. Let {yn} be a sequence such that yn → y in B. Using (2.2) and for each t ∈ [0, 1], we have ∣∣Tyn(t) −Ty(t)∣∣ ≤∫ t 0 (t−s)q−1 Γ(q) ∣∣∣f(s,yn(s))−f(s,y(s))∣∣∣ds + ∣∣∣t2 − 3t + 1 ∆ ∣∣∣×∫ η 0 Φ(s) ∣∣∣f(s,yn(s))−f(s,y(s))∣∣∣ds + ∣∣∣∣η2(1 − t) + ηt(t− 2)∆ ∣∣∣∣×∫ 1 0 Ψ∗(s) ∣∣∣f(s,yn(s))−f(s,y(s))∣∣∣ds ≤ ∫ t 0 (t−s)q−1 Γ(q) max s∈[0,1] ∣∣∣f(s,yn(s))−f(s,y(s))∣∣∣ds+ 1 |∆| × ∫ η 0 Φ(s) max s∈[0,1] ∣∣∣f(s,yn(s))−f(s,y(s))∣∣∣ds+ |η| |∆| × ∫ 1 0 Ψ∗(s) max s∈[0,1] ∣∣∣f(s,yn(s)) −f(s,y(s))∣∣∣ds ≤ ‖f ( ·,yn(·) ) −f ( ·,y(·) ) ‖ Γ(q) × ∫ t 0 (t−s)q−1ds+ 1 |η −η2| × ∫ η 0 Φ(s)ds + ∣∣∣∣ ηη −η2 ∣∣∣∣× ∫ 1 0 Ψ∗(s)ds ≤ ∣∣∣∣(η + 1)(ηq−2 + 1)Γ(q + 1) ∣∣∣∣∥∥∥f(·,yn(·))−f(·,y(·))∥∥∥. 84 KRUSHNA AND PRASAD Since f is continuous, we have ∥∥∥Tyn(t) −Ty(t)∥∥∥ ≤ ∣∣∣∣(η + 1)(ηq−2 + 1)Γ(q + 1)(n− 1) ∣∣∣∣∥∥∥f(·,yn(·))−f(·,y(·))∥∥∥ → 0 as n →∞. Therefore the operator T is continuous. Step 2. The operator T maps bounded sets in to bounded sets in B. Now we will show that for any ϑ > 0, there exits a positive constant m∗ such that for each y ∈ Bϑ = { y ∈ B : ‖y‖∞ ≤ ϑ } , we have ‖Ty‖∞ ≤ m∗. By the condition (A2) and (2.2), for each t ∈ [0, 1], we have |Ty(t)| ≤ ∫ t 0 (t−s)q−1 Γ(q) ∣∣∣f(s,y(s))∣∣∣ds + ∣∣∣∣t2 − 3t + 1∆ ∣∣∣∣× ∫ η 0 Φ(s) ∣∣∣f(s,y(s))∣∣∣ds + ∣∣∣∣η(1 − t) + ηt(t− 2)∆ ∣∣∣∣× ∫ 1 0 Ψ∗(s)f ( s,y(s) ) ds ≤M {∫ t 0 (t−s)q−1 Γ(q) ds + 1 |∆| × ∫ η 0 Φ(s)ds + ∣∣∣ η ∆ ∣∣∣×∫ 1 0 Ψ∗(s)ds } ≤M ∣∣∣∣(η + q)(1 + ηq−2)Γ(q + 1)(η − 1) ∣∣∣∣ . Thus ‖Ty‖∞ ≤M ∣∣∣∣(η + q)(1 + ηq−2)Γ(q + 1)(η − 1) ∣∣∣∣ = m∗. Step 3. The operator T maps bounded sets into equicontinuous sets B. Let t1, t2 ∈ (0, 1], t1 < t2, Bϑ be a bounded set of B as in Step 2 and y ∈ Bϑ. Then |Ty(t2) −Ty(t1)| ≤ ∫ t1 0 [(t2 −s)q−1 − (t1 −s)q−1] Γ(q) f ( s,y(s) ) ds− ∫ t2 t1 (t2 −s)q−1 Γ(q) f ( s,y(s) ) ds − [ (t22 − 3t2 + 1) − (t21 − 3t1 + 1) ∆ ] × ∫ η 0 f ( s,y(s) ) Φ(s)ds − [ η2(t22 − t21) + η(t21 − t22 + 2t2 − 2t1) ∆ ] × ∫ 1 0 f ( s,y(s) ) ds ≤M {[(t2 − t1)q − (t2 − t1)q Γ(q) ] − (t22 − t21) − 3(t2 − t1) ∆ [ ηq + qηq−1 + q(q − 1)ηq−2 ] − (1 + q2)η2 [ (η − 1)(t22 − t21) + (2t2 − 2t1) ] ∆ } . As t2 → t1, the right hand side of the above inequality tends to zero. From Steps 1 to 3, we can conclude that T : B →B is completely continuous. Step 4. The set A = { y ∈B : y = λTy for some 0 < λ < 1 } is bounded. Let y ∈ A, then y = λTy for some 0 < λ < 1. Therefore, for each t ∈ [0, 1], we have y(t) =λ {∫ t 0 (t−s)q−1 Γ(q) f ( s,y(s) ) ds− [ t2 − 3t + 1 ∆ ] × ∫ η 0 Φ(s)f ( s,y(s) ) ds − [ η2(t− 1) + ηt(2 − t) ∆ ] × ∫ 1 0 Ψ∗(s)f ( s,y(s) ) ds } EXISTENCE OF SOLUTIONS TO THE CAPUTO TYPE FBVPS 85 and ∣∣∣Ty(t)∣∣∣ ≤Mλ {∫ t 0 (t−s)q−1 Γ(q) ds + ∣∣∣∣t2 − 3t + 1∆ ∣∣∣∣× ∫ η 0 Φ(s)ds + ∣∣∣∣η2(t− 1) + ηt(2 − t)∆ ∣∣∣∣× ∫ 1 0 Ψ∗(s)ds } ≤Mλ {∫ t 0 (t−s)q−1 Γ(q) ds + ∫ η 0 Φ(s) ∆ ds + η ∫ 1 0 Ψ∗(s) ∆ ds } ≤ M(1 + η)(1 + ηq−1) Γ(q + 1) . Thus for every t ∈ [0, 1], we have ∥∥Ty∥∥∞ ≤M ∣∣∣∣(1 + η)(1 + ηq−1)Γ(q + 1) ∣∣∣∣ . This shows that the set A is bounded. By Schaefer’s fixed point theorem, the operator T has a fixed point which is a solution of the fractional order boundary value problem (1.1)-(1.2). � 3. Examples In this section, we give two examples to illustrate the usefulness of our main results. Example 3.1 Consider the fractional order three-point boundary value problem, (3.1) CD2.6y(t) = 3e−2ty (19 + 5e2t)(3 + y) , t ∈ (0, 1), (3.2)   y(0) + y′(0) + y′′(0) =0, y (2 5 ) + y′ (2 5 ) + y′′ (2 5 ) =0, y(1) + y′(1) + y′′(1) =0. For y,y ∈ [0,∞) and t ∈ [0, 1], we have |f(t,y) −f(t,y)| = 3e−2t 19 + 5e2t ∣∣∣∣ y3 + y − y3 + y ∣∣∣∣ ≤ 924∣∣y −y∣∣. Now we check the condition (2.4) with ξ = 9 24 , ζ = ∣∣∣∣ 924 ( 2 5 + 1 )[( 2 5 )0.6 + 1 )] Γ(3.6) (−3 5 ) ∣∣∣∣ = 0.42 < 1. Then all conditions of Theorem 2.3 are satisfied. Thus by Theorem 2.3 the fractional order boundary value problem (3.1)-(3.2) has unique solution on [0, 1]. Example 3.2 Consider the fractional order three-point boundary value problem, (3.3) CD2.5y(t) = e−ty (1 + et)(1 + y) , t ∈ (0, 1), (3.4)   y(0) + y′(0) + y′′(0) =0, y (1 2 ) + y′ (1 2 ) + y′′ (1 2 ) =0, y(1) + y′(1) + y′′(1) =0. By simple algebraic calculations, one can determine m∗ = ∣∣∣∣ 32 ( 1 + 0.50.5 )] Γ(3.5) (−1 2 ) ∣∣∣∣ = 1.6 and M = 12. Then the fractional order boundary value problem (3.3)-(3.4) satisfies all conditions of Theorem 2.5. Hence it has unique solution on [0, 1]. 86 KRUSHNA AND PRASAD References [1] Z. Bai and Y. Zhang, Solvability of fractional three-point boundary value problems with nonlinear growth, Appl. Math. Comput., 218(2011), 1719–1725. [2] M. Benchohra, J. Henderson, S. K. Ntoyuas and A. Ouahab, Existence results for fractional order functional differential equations with infinite delay, J. Math. Anal. Appl., 338 (2008), 1340–1350. [3] M. Benchohra, S. Hamani, S.K. Ntouyas, Boundary value problems for differential equations with fractional order and nonlocal conditions, Nonlinear Anal. TMA., 71(2009), 2391–2396. [4] M. Feng, X. Zhang and W. Ge, New existence results for higher-order nonlinear fractional differential equation with integral boundary conditions, Bound. Value Probl., 2011(2011), Article ID 720702. [5] A. A. Kilbas and J. J. Trujillo, Differential equations of fractional order methods, results, problems, Appl. Anal., 78(2001), 153–192. [6] A. A. Kilbas, H. M. Srivasthava and J. J. Trujillo, Theory and Applications of Fractional Differential Equations, North-Holland Mathematics Studies, 204, Elsevier Science, Amsterdam, 2006. [7] R. A. Khan, M. Rehman and J. Henderson, Existence and uniqueness of solutions for nonlinear fractional differential equations with integral boundary conditions, Fract. Differ. Calc., 1(2011), 29–43. [8] R. A. Khan and H. Khan, Existence of solution for a three-point boundary value problem of fractional differential equation, Journal of Fractional Calculus and Applications, 5(2014), 156–164. [9] K. S. Miller and B. Ross, An Introduction to Fractional Calculus and Fractional Differential Equations, John Wiley and Sons, New York, 1993. [10] Z. Ouyang and G. Li, Existence of the solutions for a class of nonlinear fractional order three-point boundary value problems with resonance, Bound. Value Probl., 2012(2012), Article ID 68, 1–13. [11] I. Podulbny, Fractional Diffrential Equations, Academic Press, San Diego, 1999. [12] K. R. Prasad and B. M. B. Krushna, Multiple positive solutions for a coupled system of Riemann–Liouville fractional order two-point boundary value problems, Nonlinear Stud., 20(2013), 501–511. [13] K. R. Prasad and B. M. B. Krushna, Eigenvalues for iterative systems of Sturm–Liouville fractional order two-point boundary value problems, Fract. Calc. Appl. Anal., 17(2014), 638–653. [14] K. R. Prasad and B. M. B. Krushna, Existence of solutions for a coupled system of three-point fractional order boundary value problems, Differ. Equ. Appl., 7(2015), 187–200. [15] M. Rehman and R. A. Khan, Existence and uniqueness of solutions for multi-point boundary value problems for fractional differential equations, Appl. Math. Lett., 23 (2010), 1038–1044. [16] M. Rehman, R. A. Khan and N. A. Asif, Three point boundary value problems for nonlinear fractional differential equations, Acta Mathematica Scientia, 31(2011), 1337–1346. [17] A. Shi and S. Zhang, Upper and lower solutions method and a fractional differential equation boundary value problem, Electron. J. Qual. Theory Differ. Equ., 30(2009), 1–13. [18] G. Wang, S. K. Ntouyas and L. Zhang, Positive solutions of the three-point boundary value problem for fractional order differential equations with an advanced argument, Advances in Difference Equations, 2011(2011), Article ID 2. [19] J. R. Wang, L. Lv and W. Wei, Differential equations of fractional order α ∈ (2, 3) with boundary value conditions in abstract Banach spaces, Math. Commun., 17(2012), 371–387. [20] S. Zhang, Positive solutions for boundary value problems of nonlinear fractional differential equations, Electron. J. Differential Equations, 36(2006), 1–12. 1Department of Mathematics, MVGR College of Engineering (Autonomous), Vizianagaram, 535 005, India 2Department of Applied Mathematics, Andhra University, Visakhapatnam, 530 003, India ∗Corresponding author: muraleebalu@yahoo.com