International Journal of Analysis and Applications ISSN 2291-8639 Volume 6, Number 1 (2014), 63-81 http://www.etamaths.com EXISTENCE OF MULTIPLE POSITIVE SOLUTIONS FOR p-LAPLACIAN FRACTIONAL ORDER BOUNDARY VALUE PROBLEMS K. R. PRASAD1 AND B. M. B. KRUSHNA2,∗ Abstract. This paper deals with the existence of at least one and multiple positive solutions for p-Laplacian fractional order two-point boundary value problems, D q2 0+ ( φp ( D q1 0+ y(t) )) = f(t,y(t)), t ∈ (0, 1), y(j)(0) = 0, j = 0, 1, 2, · · ·,n− 2, y(q4)(1) = 0, φp ( D q1 0+ y(0) ) = 0 = D q3 0+ ( φp ( D q1 0+ y(1) )) , where q2 ∈ (1, 2],q1 ∈ (n − 1,n],n ≥ 2,q3 ∈ (0, 1], q4 ∈ [1,q1 − 1] is a fixed integer, φp(y) = |y|p−2y, p > 1, φ−1p = φq, 1/p + 1/q = 1, by applying Krasnosel’skii and five functionals fixed point theorems. 1. Introduction The goal of differential equations is to understand the phenomena of nature by developing mathematical models. Fractional calculus is the field of mathematical analysis, which deals with investigation and applications of derivatives and inte- grals of an arbitrary order. Among all, a class of differential equations governed by nonlinear differential operators appears frequently and generated great deal of interest in studying such problems. In this theory, the most applicable operator is the classical p-Laplacian, given by φp(y) = |y|p−2y, p > 1. These types of problems arise in applied fields such as turbulent flow of a gas in a porous medium, modeling of viscoelastic flows, biophysics, plasma physics and material science. The existence of positive solutions of boundary value problems (BVPs) as- sociated with integer order differential equations were studied by many authors [11, 1, 9, 2, 19] and extended to p-Laplacian boundary value problems [17, 14, 4, 23]. Later, these results are further extended to fractional order boundary value prob- lems [6, 10, 5, 7, 8, 20, 21, 22] by utilizing various fixed point theorems on cones. In recent years, researchers are concentrating on the theory of fractional order bound- ary value problems related with p-Laplacian operator. 2010 Mathematics Subject Classification. 26A33, 34B18, 35J05. Key words and phrases. Fractional derivative, p-Laplacian, boundary value problem, two- point, Green’s function, positive solution. c©2014 Authors retain the copyrights of their papers, and all open access articles are distributed under the terms of the Creative Commons Attribution License. 63 64 PRASAD AND KRUSHNA In 2012, Chai [7] investigated the existence and multiplicity of positive solutions for a class of boundary value problem of fractional differential equation with p- Laplacian operator, D β 0+(φp(D α 0+u(t))) + f(t,u(t)) = 0, 0 < t < 1, u(0) = 0,u(1) + σD γ 0+u(1) = 0,D α 0+u(0) = 0, where 1 < α ≤ 2, 0 < β,γ ≤ 1, 0 ≤ α−γ−1,σ is a positive number, Dα 0+ ,D β 0+ ,D γ 0+ are the standard Riemann-Liouville fractional order derivatives. The purpose of this paper is to establish the existence of at least one and multiple positive solutions for p-Laplacian fractional order boundary value problems, (1.1) D q2 0+ ( φp ( D q1 0+ y(t) )) = f(t,y(t)), t ∈ (0, 1), (1.2) y(j)(0) = 0, j = 0, 1, 2, · · ·,n− 2, y(q4)(1) = 0, φp ( D q1 0+ y(0) ) = 0 = D q3 0+ ( φp ( D q1 0+ y(1) )) ,   where q2 ∈ (1, 2],q1 ∈ (n− 1,n],n ≥ 2,q3 ∈ (0, 1], q4 ∈ [1,q1 − 1] is a fixed integer, φp(y) = |y|p−2y, p > 1, φ−1p = φq, 1/p + 1/q = 1, f : [0, 1] × R + → R+ is continuous and D qi 0+ , for i = 1, 2, 3 are the standard Riemann-Liouville fractional order derivatives. Define the nonnegative extended real numbers f0,f 0,f∞ and f ∞ by f0 = lim y→0+ min t∈[0,1] f(t,y) φp(y) , f0 = lim y→0+ max t∈[0,1] f(t,y) φp(y) , f∞ = lim y→∞ min t∈[0,1] f(t,y) φp(y) and f∞ = lim y→∞ max t∈[0,1] f(t,y) φp(y) , and also assume that they will exist. The rest of the paper is organized as follows. In Section 2, we construct the Green functions for the homogeneous BVPs corresponding to (1.1)-(1.2) and estimate the bounds for the Green functions. In Section 3, we establish criteria for the existence of at least one positive solution for p-Laplacian fractional order BVP (1.1)-(1.2), by using Krasnosel’skii fixed point theorem. In Section 4, we derive sufficient conditions for the existence of at least three positive solutions for the p-Laplacian fractional order BVP (1.1)-(1.2), by applying five functionals fixed point theorem. We also establish the existence of at least 2k−1 positive solutions for an arbitrary positive integer k. In Section 5, as an application, the results are demonstrated with examples. 2. Green Functions and Bounds In this section, we construct the Green functions for the homogeneous BVPs and estimate the bounds for the Green functions, which are essential to establish the main results. Let G(t,s) be the Green’s function for the homogeneous BVP, (2.1) −Dq1 0+ y(t) = 0, t ∈ (0, 1), (2.2) y(j)(0) = 0, j = 0, 1, · · ·,n− 2, y(q4)(1) = 0. p-LAPLACIAN FRACTIONAL ORDER BOUNDARY VALUE PROBLEMS 65 Lemma 2.1. Let h(t) ∈ C[0, 1]. Then the fractional order differential equation, (2.3) D q1 0+ y(t) + h(t) = 0, t ∈ (0, 1), satisfying (2.2) has a unique solution, y(t) = ∫ 1 0 G(t,s)h(s)ds, where (2.4) G(t,s) = { G1(t,s), 0 ≤ t ≤ s ≤ 1, G2(t,s), 0 ≤ s ≤ t ≤ 1, G1(t,s) = tq1−1(1 −s)q1−q4−1 Γ(q1) , G2(t,s) = tq1−1(1 −s)q1−q4−1 − (t−s)q1−1 Γ(q1) . Proof. Let y(t) ∈ C[q1]+1[0, 1] be the solution of fractional order differential equa- tion (2.3) satisfying (2.2). Then y(t) = −1 Γ(q1) ∫ t 0 (t−s)q1−1h(s)ds + c1tq1−1 + c2tq1−2 + · · · + cntq1−n. From (2.2), ci = 0, i = 2, 3, · · ·,n and c1 = ∫ 1 0 (1−s)q1−q4−1 Γ(q1) h(s)ds. Thus, the unique solution of (2.3) with (2.2) is y(t) = −1 Γ(q1) ∫ t 0 (t−s)q1−1h(s)ds + tq1−1 Γ(q1) ∫ 1 0 (1 −s)q1−q4−1h(s)ds = ∫ 1 0 G(t,s)h(s)ds, where G(t,s) is the Green’s function and given in (2.4). � Lemma 2.2. Let z(t) ∈ C[0, 1]. Then the fractional order differential equation, (2.5) D q2 0+ ( φp ( D q1 0+ y(t) )) = z(t), t ∈ (0, 1), satisfying (2.6) φp ( D q1 0+ y(0) ) = 0,D q3 0+ ( φp ( D q1 0+ y(1) )) = 0, has a unique solution, y(t) = ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)z(τ)dτ ) ds, where (2.7) H(t,s) = { tq2−1(1−s)q2−q3−1 Γ(q2) , 0 ≤ t ≤ s ≤ 1, tq2−1(1−s)q2−q3−1−(t−s)q2−1 Γ(q2) , 0 ≤ s ≤ t ≤ 1. Here H(t,s) is the Green’s function for −Dq2 0+ ( φp(x(t)) ) = 0, t ∈ (0, 1), φp(x(0)) = 0, D q3 0+ ( φp(x(1)) ) = 0. 66 PRASAD AND KRUSHNA Proof. An equivalent integral equation for (2.5) is given by φp ( D q1 0+ y(t) ) = 1 Γ(q2) ∫ t 0 (t− τ)q2−1z(τ)dτ + c1tq2−1 + c2tq2−2. By (2.6), one can determine c2 = 0 and c1 = −1 Γ(q2) ∫ 1 0 (1 − τ)q2−q3−1z(τ)dτ. Then, φp ( D q1 0+ y(t) ) = 1 Γ(q2) ∫ t 0 (t− τ)q2−1z(τ)dτ − tq2−1 Γ(q2) ∫ 1 0 (1 − τ)q2−q3−1z(τ)dτ = − ∫ 1 0 H(t,τ)z(τ)dτ. Therefore, φ−1p ( φp ( D q1 0+ y(t) )) = −φ−1p (∫ 1 0 H(t,τ)z(τ)dτ ) . Consequently, D q1 0+ y(t) + φq (∫ 1 0 H(t,τ)z(τ)dτ ) = 0. Hence, y(t) = ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)z(τ)dτ ) ds is the solution of fractional order BVP (2.5), (1.2). � Lemma 2.3. For t ∈ I = [ 1 4 , 3 4 ] , the Green’s function G(t,s) given in (2.4) satisfies the following inequalities (i) G(t,s) ≥ 0, for all (t,s) ∈ [0, 1] × [0, 1], (ii) G(t,s) ≤ G(1,s), for all (t,s) ∈ [0, 1] × [0, 1], (iii) G(t,s) ≥ ξG(1,s), for all (t,s) ∈ I × [0, 1], where ξ = ( 1 4 )q1−1 . Proof. The Green’s function G(t,s) of (2.1), (2.2) is given in (2.4). For 0 ≤ t ≤ s ≤ 1, G1(t,s) = 1 Γ(q1) [ tq1−1(1 −s)q1−q4−1 ] ≥ 0. For 0 ≤ s ≤ t ≤ 1, G2(t,s) = 1 Γ(q1) [ tq1−1(1 −s)q1−q4−1 − (t−s)q1−1 ] ≥ 1 Γ(q1) [ tq1−1(1 −s)q1−q4−1 − (t− ts)q1−1 ] = tq1−1 Γ(q1) [( 1 + δs + q4(q4 + 1) 2 s2 + · · · ) − 1 ] (1 −s)q1−1 = tq1−1 Γ(q1) [ q4s + O(s 2) ] (1 −s)q1−1 ≥ 0. Hence the Green’s function G(t,s) is nonnegative. For 0 ≤ t ≤ s ≤ 1, ∂G1(t,s) ∂t = 1 Γ(q1) [ (q1 − 1)tq1−2(1 −s)q1−q4−1 ] ≥ 0. p-LAPLACIAN FRACTIONAL ORDER BOUNDARY VALUE PROBLEMS 67 Therefore, G1(t,s) is increasing in t, which implies G1(t,s) ≤ G1(1,s). Now, for 0 ≤ s ≤ t ≤ 1, ∂G2(t,s) ∂t = 1 Γ(q1) [ (q1 − 1)tq1−2(1 −s)q1−q4−1 − (q1 − 1)(t−s)q1−2 ] ≥ 1 Γ(q1) [ (q1 − 1)tq1−2(1 −s)q1−q4−1 − (q1 − 1)(t− ts)q1−2 ] = (q1 − 1)tq1−2 Γ(q1) [ 1 − ( 1 − (q4 − 1)s + (q4 − 1)(q4 − 2) 2 s2 + · · · )] (1 −s)q1−q4−1 = (q1 − 1)tq1−2 Γ(q1) [ (q4 − 1)s + O(s2) ] (1 −s)q1−q4−1 ≥ 0. Therefore, G2(t,s) is increasing in t, which implies G2(t,s) ≤ G2(1,s). Let 0 ≤ t ≤ s ≤ 1 and t ∈ I. Then G1(t,s) = 1 Γ(q1) [ tq1−1(1 −s)q1−q4−1 ] =tq1−1 1 Γ(q1) [ (1 −s)q1−q4−1 ] =tq1−1G1(1,s) ≥ (1 4 )q1−1 G1(1,s). Let 0 ≤ s ≤ t ≤ 1 and t ∈ I. Then G2(t,s) = 1 Γ(q1) [ tq1−1(1 −s)q1−q4−1 − (t−s)q1−1 ] ≥ 1 Γ(q1) [ tq1−1(1 −s)q1−q4−1 − (t− ts)q1−1 ] =tq1−1G2(1,s) ≥ (1 4 )q1−1 G2(1,s). Hence the result. � Lemma 2.4. For t,s ∈ [0, 1], the Green’s function H(t,s) given in (2.7) satisfies the following inequalities (i) H(t,s) ≥ 0, (ii) H(t,s) ≤ H(s,s). Proof. The Green’s function H(t,s) is given in (2.7). For 0 ≤ t ≤ s ≤ 1, H(t,s) = 1 Γ(q2) [ tq2−1(1 −s)q2−q3−1 ] ≥ 0. 68 PRASAD AND KRUSHNA For 0 ≤ s ≤ t ≤ 1, H(t,s) = 1 Γ(q2) [ tq2−1(1 −s)q2−q3−1 − (t−s)q2−1 ] ≥ 1 Γ(q2) [ tq2−1(1 −s)q2−q3−1 − (t− ts)q2−1 ] = tq2−1 Γ(q2) [ (1 −s)−q3 − 1 ] (1 −s)q2−1 = tq2−1 Γ(q2) [( 1 + q3s + q3(q3 + 1) 2 s2 + · · · ) − 1 ] (1 −s)q2−1 = tq2−1 Γ(q2) [ q3s + O(s 2) ] (1 −s)q2−1 ≥ 0. For 0 ≤ t ≤ s ≤ 1, ∂H(t,s) ∂t = 1 Γ(q2) [(q2 − 1)tq2−2(1 −s)q2−q3−1] ≥ 0. Therefore, H(t,s) is increasing in t, for s ∈ [0, 1], which implies H(t,s) ≤ H(s,s). Now, for 0 ≤ s ≤ t ≤ 1, ∂H(t,s) ∂t = 1 Γ(q2) [ (q2 − 1)tq2−2(1 −s)q2−q3−1 − (q2 − 1)(t−s)q2−2 ] ≤ (q2 − 1) Γ(q2) [ (1 −s)q2−q3−1 − (1 −s)q2−2 ] = (q2 − 1) Γ(q2) [ (1 −s)−q3+1 − 1 ] (1 −s)q2−2 = (q2 − 1) Γ(q2) [( 1 − (1 −q3)s + (1 −q3)(−q3) 2 s2 + · · · ) − 1 ] (1 −s)q2−2 = (q2 − 1) Γ(q2) [ (q3 − 1)s + O(s2) ] (1 −s)q2−2 ≤ 0. Therefore, H(t,s) is decreasing in t, for s ∈ [0, 1] which implies H(t,s) ≤ H(s,s). Hence the result. � Lemma 2.5. Let µ ∈ ( 1 4 , 3 4 ). Then the Green’s function H(t,s) holds the inequality, (2.8) min t∈I H(t,s) ≥ δ∗(s)H(s,s), for 0 < s < 1, where (2.9) δ∗(s) = { ( 3 4 )q2−1(1−s)q2−q3−1−( 3 4 −s)q2−1 sq2−1(1−s)q2−q3−1 , s ∈ (0,µ], 1 (4s)q2−1 , s ∈ [µ, 1). Proof. For s ∈ (0, 1), H(t,s) is increasing in t for t ≤ s and decreasing in t for s ≤ t. p-LAPLACIAN FRACTIONAL ORDER BOUNDARY VALUE PROBLEMS 69 We define h1(t,s) = [tq2−1(1 −s)q2−q3−1 − (t−s)q2−1] Γ(q2) h2(t,s) = [tq2−1(1 −s)q2−q3−1] Γ(q2) , and H(s,s) = 1 Γ(q2) [ sq2−1(1 −s)q2−q3−1 ] . Then, min t∈I H(t,s) =   h1( 3 4 ,s), s ∈ (0, 1 4 ], min{h1( 34,s),h2( 1 4 ,s)}, s ∈ [ 1 4 , 3 4 ], h2( 1 4 ,s), s ∈ [ 3 4 , 1), = { h1( 3 4 ,s), s ∈ (0,µ], h2( 1 4 ,s), s ∈ [µ, 1), =   ( 3 4 )q2−1(1−s)q2−q3−1−( 3 4 −s)q2−1 Γ(q2) , s ∈ (0,µ], 1 Γ(q2) (1−s)q2−q3−1 4q2−1 , s ∈ [µ, 1), ≥ { ( 3 4 )q2−1(1−s)q2−q3−1−( 3 4 −s)q2−1 sq2−1(1−s)q2−q3−1 H(s,s), s ∈ (0,µ], 1 (4s)q2−1 H(s,s), s ∈ [µ, 1), = δ∗(s)H(s,s). � Let B = {y : y ∈ C[0, 1]} be the real Banach space equipped with the norm ‖y‖ = max t∈[0,1] |y(t)|. Define a cone P ⊂ B by P = { y ∈ B : y(t) ≥ 0, t ∈ [0, 1] and min t∈I y(t) ≥ ξ‖y‖ } . Let K = 1∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)dτ ) ds and L = 1∫ s∈I ξG(1,s)φq (∫ τ∈I δ ∗(τ)H(τ,τ)dτ ) ds . Let T : P → B be the operator defined by (2.10) Ty(t) = ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds. If y ∈ P is a fixed point of T, then y satisfies (2.10) and hence y is a positive solution of the p-Laplacian fractional order BVP (1.1)-(1.2). Lemma 2.6. The operator T defined by (2.10) is a self map on P . 70 PRASAD AND KRUSHNA Proof. Let y ∈ P . Clearly, Ty(t) ≥ 0, for all t ∈ [0, 1], and Ty(t) = ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds so that ‖Ty‖≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds. Next, if y ∈ P , then by the above inequality we have min t∈I Ty(t) = min t∈I ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≥ ξ ∫ 1 0 G(1,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≥ ξ‖Ty‖. Hence, Ty ∈ P and so T : P → P. Standard arguments involving the Arzela-Ascoli theorem shows that T is completely continuous. � 3. Existence of at Least One Positive Solution In this section, we establish criteria for the existence of at least one positive solution of the p-Laplacian fractional order BVP (1.1)-(1.2) by using Krasnosel’skii fixed point theorem. To establish the existence of at least one positive solution for p-Laplacian frac- tional order BVP (1.1)-(1.2) by employing the following Krasnosel’skii fixed point theorem. Theorem 3.1. [15] Let X be a Banach Space, P ⊆ X be a cone and suppose that Ω1, Ω2 are open subsets of X with 0 ∈ Ω1 and Ω1 ⊂ Ω2. Suppose further that T : P ∩ (Ω2\Ω1) → P is completely continuous operator such that either (i) ‖ Tu ‖≤‖ u ‖, u ∈ P ∩∂Ω1 and ‖ Tu ‖≥‖ u ‖, u ∈ P ∩∂Ω2, or (ii) ‖ Tu ‖≥‖ u ‖, u ∈ P ∩∂Ω1 and ‖ Tu ‖≤‖ u ‖, u ∈ P ∩∂Ω2 holds. Then T has a fixed point in P ∩ (Ω2\Ω1). Theorem 3.2. If f0 = 0 and f∞ = ∞, then the p-Laplacian fractional order BVP (1.1)-(1.2) has at least one positive solution that lies in P . Proof. Let T be the cone preserving, completely continuous operator defined by (2.10). Since f0 = 0, we may choose H1 > 0 so that max t∈[0,1] f(t,y) φp(y) ≤ η1, for 0 < y ≤ H1, where η1 > 0 satisfies η q−1 1 ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)dτ ) ds = η q−1 1 1 K ≤ 1. p-LAPLACIAN FRACTIONAL ORDER BOUNDARY VALUE PROBLEMS 71 Thus, if y ∈ P and ‖y‖ = H1, then we have Ty(t) = ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y)dτ ) ds ≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)η1φp(y)dτ ) ds = ∫ 1 0 G(1,s)η q−1 1 φq (∫ 1 0 H(τ,τ)dτ ) yds ≤ ηq−11 ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)dτ ) ds‖y‖ = η q−1 1 1 K ‖y‖≤‖y‖. Therefore, ‖Ty‖≤‖y‖. Now, if we let Ω1 = {y ∈ B : ‖y‖ < H1}, then (3.1) ‖Ty‖≤‖y‖, for y ∈ P ∩∂Ω1. Further, since f∞ = ∞, there exists H 2 > 0 such that min t∈[0,1] f(t,y) φp(y) ≥ η2, for y ≥ H 2 , where η2 > 0 is chosen such that η q−1 2 ξ 2 ∫ s∈I G(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)dτ ) ds = η q−1 2 ξ 2 1 L ≥ 1. Let H2 = max { 2H1, 1 ξ H 2 } , and define Ω2 = {y ∈ B : ‖y‖ < H2}. If y ∈ P ∩∂Ω2 and ‖y‖ = H2, then min t∈I y(t) ≥ ξ‖y‖≥ H 2 , 72 PRASAD AND KRUSHNA and so Ty(t) = ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y)dτ ) ds ≥ ∫ s∈I ξG(1,s)φq (∫ 1 0 H(s,τ)f(τ,y)dτ ) ds ≥ ξ ∫ s∈I G(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)η2φp(y)dτ ) ds = ξη q−1 2 ∫ s∈I G(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)dτ ) yds ≥ ξηq−12 ∫ s∈I G(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)dτ ) ξ‖y‖ds = ξ2η q−1 2 ∫ s∈I G(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)dτ ) ds‖y‖ = η q−1 2 ξ 2 1 L ‖y‖ ≥‖y‖. Hence, (3.2) ‖Ty‖≥‖y‖, for y ∈ P ∩∂Ω2. An application of Theorem 3.1 to (3.1) and (3.2) yields a fixed point of T that lies in P ∩ (Ω2\Ω1). This fixed point is the solution of the p-Laplacian fractional order BVP (1.1)-(1.2). � Theorem 3.3. If f0 = ∞ and f∞ = 0, then the p-Laplacian fractional order BVP (1.1)-(1.2) has at least one positive solution that lies in P . Proof. Let T be the cone preserving, completely continuous operator defined by (2.10). Since f0 = ∞, we choose J1 > 0 such that min t∈[0,1] f(t,y) φp(y) ≥ η1, for 0 < y ≤ J 1, where η1 > 0 satisfies (η1) q−1ξ2 ∫ s∈I G(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)dτ ) ds = (η1) q−1ξ2 1 L ≥ 1. In this case, we define Ω1 = {y ∈ B : ‖y‖ < J1}, p-LAPLACIAN FRACTIONAL ORDER BOUNDARY VALUE PROBLEMS 73 we have f(τ,y) ≥ η1φp(y),τ ∈ I, and moreover y(t) ≥ ξ‖y‖, t ∈ I and so Ty(t) = ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y)dτ ) ds ≥ ∫ s∈I ξG(1,s)φq (∫ 1 0 H(s,τ)f(τ,y)dτ ) ds ≥ ξ ∫ s∈I G(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)η1φp(y)dτ ) ds = ξ(η1) q−1 ∫ s∈I G(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)dτ ) yds ≥ ξ(η1) q−1 ∫ s∈I G(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)dτ ) ξ‖y‖ds ≥ ξ2(η1) q−1 ∫ s∈I G(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)dτ ) ds‖y‖ = (η1) q−1ξ2 1 L ‖y‖ ≥‖y‖. Thus, (3.3) ‖Ty‖≥‖y‖, for y ∈ P ∩∂Ω1. Now, since f∞ = 0, there exists J 2 > 0 such that max t∈[0,1] f(t,y) φp(y) ≤ η2, for y ≥ J 2 , where η2 > 0 satisfies (η2) q−1 ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)dτ ) ds = (η2) q−1 1 K ≤ 1. It follows that f(t,y) ≤ η2φp(y), for y ≥ J 2 . We establish the result in two subcases. Case(i) : f is bounded. Suppose N > 0 is such that maxt∈[0,1] f(t,y) ≤ N, for all 0 < y < ∞. In this case, we may choose J2 = max { 2J1,Nq−1 1 K } , and let Ω2 = {y ∈ B : ‖y‖ < J2}. 74 PRASAD AND KRUSHNA Then for y ∈ P ∩∂Ω2 and ‖y‖ = J2, we have Ty(t) = ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y)dτ ) ds ≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(s,τ)Ndτ ) ds ≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)dτ ) Nq−1ds ≤ Nq−1 ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)dτ ) ds = Nq−1 1 K = J2 = ‖y‖, and therefore (3.4) ‖Ty‖≤‖y‖, for y ∈ P ∩∂Ω2. Case(ii) : f is unbounded. Let J2 > max{2J1,J 2 } be such that f(t,y) ≤ f(t,J2), for 0 < y ≤ J2, and let Ω2 = {y ∈ B : ‖y‖ < J2}. Choosing y ∈ P ∩ ∂Ω2 with ‖y‖ = J2, we have Ty(t) = ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y)dτ ) ds ≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(s,τ)f(τ,y)dτ ) ds ≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)f(τ,J2)dτ ) ds ≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)η2φp(J 2)dτ ) ds = (η2) q−1 ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)dτ ) dsJ2 = (η2) q−1 1 K J2 ≤ J2 = ‖y‖. And so (3.5) ‖Ty‖≤‖y‖, for y ∈ P ∩∂Ω2. An application of Theorem 3.1 to (3.3), (3.4) and (3.5) yields a fixed point of T that lies in P ∩ (Ω2\Ω1). This fixed point is the solution of the p-Laplacian fractional order BVP (1.1)-(1.2). � 4. Existence of Multiple Positive Solutions In this section, we derive sufficient conditions for the existence of at least three positive solutions for the p-Laplacian fractional order BVP (1.1)-(1.2), by applying five functionals fixed point theorem. We also establish the existence of at least p-LAPLACIAN FRACTIONAL ORDER BOUNDARY VALUE PROBLEMS 75 2k − 1 positive solutions for an arbitrary positive integer k. Let γ,β,θ be nonnegative continuous convex functionals on P and α,ψ be nonnegative continuous concave functionals on P , then for nonnegative numbers h′,a′,b′,d′ and c′, convex sets are defined. P(γ,c′) = {y ∈ P : γ(y) < c′}, P(γ,α,a′,c′) = {y ∈ P : a′ ≤ α(y); γ(y) ≤ c′}, Q(γ,β,d′,c′) = {y ∈ P : β(y) ≤ d′; γ(y) ≤ c′}, P(γ,θ,α,a′,b′,c′) = {y ∈ P : a′ ≤ α(y); θ(y) ≤ b′; γ(y) ≤ c′}, Q(γ,β,ψ,h′,d′,c′) = {y ∈ P : h′ ≤ ψ(y); β(y) ≤ d′; γ(y) ≤ c′}. In obtaining multiple positive solutions for the p-Laplacian fractional order B- VP (1.1)-(1.2), the following so called Five Functionals Fixed Point Theorem is fundamental. Theorem 4.1. [3] Let P be a cone in the real Banach space B. Suppose α and ψ are nonnegative continuous concave functionals on P and γ,β,θ are nonnega- tive continuous convex functionals on P, such that for some positive numbers c′ and e′, α(y) ≤ β(y) and ‖ y ‖≤ e′γ(y), for all y ∈ P(γ,c′). Suppose further that T : P(γ,c′) → P(γ,c′) is completely continuous and there exist constants h′,d′,a′ and b′ ≥ 0 with 0 < d′ < a′ such that each of the following is satisfied. (D1) {y ∈ P(γ,θ,α,a′,b′,c′) : α(y) > a′} 6= ∅ and α(Ty) > a′ for y ∈ P(γ,θ,α,a′,b′,c′), (D2) {y ∈ Q(γ,β,ψ,h′,d′,c′) : β(y) > d′} 6= ∅ and β(Ty) > d′ for y ∈ Q(γ,β,ψ,h′,d′,c′), (D3) α(Ty) > a′ provided y ∈ P(γ,α,a′,c′) with θ(Ty) > b′, (D4) β(Ty) < d′ provided y ∈ Q(γ,β,ψ,h′,d′,c′) with ψ(Ty) < h′. Then T has at least three fixed points y1,y2,y3 ∈ P(γ,c′) such that β(y1) < d′,a′ < α(y2) and d ′ < β(y3) with α(y3) < a ′. Define the nonnegative continuous concave functionals α,ψ and the nonnegative continuous convex functionals β,θ,γ on P by α(y) = min t∈I y(t),ψ(y) = min t∈I1 y(t), γ(y) = max t∈[0,1] y(t),β(y) = max t∈I1 y(t),θ(y) = max t∈I y(t), where I1 = [ 1 3 , 2 3 ] . For any y ∈ P , (4.1) α(y) = min t∈I y(t) ≤ max t∈I1 y(t) = β(y) and (4.2) ‖y‖≤ 1 ξ min t∈I y(t) ≤ 1 ξ max t∈[0,1] y(t) = 1 ξ γ(y). 76 PRASAD AND KRUSHNA Theorem 4.2. Suppose there exist 0 < a′ < b′ < b ′ ξ ≤ c′ such that f satisfies the following conditions: (C1) f(t,y(t)) < φp ( a′K ) , t ∈ [0, 1] and y ∈ [ξa′,a′], (C2) f(t,y(t)) > φp ( b′L ) , t ∈ I and y ∈ [ b′, b′ ξ ] , (C3) f(t,y(t)) < φp ( c′K ) , t ∈ [0, 1] and y ∈ [0,c′]. Then the p-Laplacian fractional order BVP (1.1)-(1.2) has at least three positive solutions y1, y2 and y3 such that β(y1) < a ′, b′ < α(y2) and a ′ < β(y3) with α(y3) < b ′. Proof. We seek three fixed points y1,y2,y3 ∈ P of T defined by (2.10). From Lemma 2.6, (4.1) and (4.2), for each y ∈ P , α(y) ≤ β(y) and ‖y‖ ≤ 1 ξ γ(y). We show that T : P(γ,c′) → P(γ,c′). Let y ∈ P(γ,c′). Then 0 ≤ y ≤ c′. We may use the condition (C3) to obtain γ(Ty) = max t∈[0,1] ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)f(τ,y(τ))dτ ) ds ≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)φp ( c′K ) dτ ) ds < c′K ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)dτ ) ds = c′. Therefore T : P(γ,c′) → P(γ,c′). Now we verify the conditions (D1) and (D2) of Theorem 4.1 are satisfied. It is obvious that b′ + b ′ ξ 2 ∈ { y ∈ P ( γ,θ,α,b′, b′ ξ ,c′ ) : α(y) > b′ } 6= ∅ and ξa′ + a′ 2 ∈ { y ∈ Q ( γ,β,ψ,ξa′,a′,c′ ) : β(y) < a′ } 6= ∅. Next, let y ∈ P(γ,θ,α,b′, b ′ ξ ,c′) or y ∈ Q(γ,β,ψ,ξa′,a′,c′). Then, b′ ≤ y ≤ b ′ ξ and ηa′ ≤ y ≤ a′. Now, we may apply the condition (C2) to get α(Ty) = min t∈I ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≥ ξ ∫ s∈I G(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)φp ( b′L ) dτ ) ds > b′L ∫ s∈I ξG(1,s)φq (∫ τ∈I δ∗(τ)H(τ,τ)dτ ) ds = b′. p-LAPLACIAN FRACTIONAL ORDER BOUNDARY VALUE PROBLEMS 77 Clearly, by the condition (C1), we have β(Ty) = max t∈I1 ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)φp ( a′K ) dτ ) ds < a′K ∫ 1 0 G(1,s)φq (∫ 1 0 H(τ,τ)dτ ) ds = a′. To see that (D3) is satisfied, let y ∈ P(γ,α,b′,c′) with θ(Ty) > b ′ ξ . Then α(Ty) = min t∈I ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≥ ξ ∫ 1 0 G(1,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≥ ξ max t∈[0,1] ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≥ ξ max t∈I ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds = ξθ(Ty) > b′. Finally, we show that (D4) holds. Let y ∈ Q(γ,β,a′,c′) with ψ(Ty) < ξa′. Then, we have β(Ty) = max t∈I1 ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≤ max t∈[0,1] ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≤ ∫ 1 0 G(1,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds = 1 ξ [ ξ ∫ 1 0 G(1,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ )] ≤ 1 ξ min t∈I ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds ≤ 1 ξ min t∈I1 ∫ 1 0 G(t,s)φq (∫ 1 0 H(s,τ)f(τ,y(τ))dτ ) ds = 1 ξ ψ(Ty) < a′. We have proved that all the conditions of Theorem 4.1 are satisfied. Therefore, the p-Laplacian fractional order BVP (1.1)-(1.2) has at least three positive solutions y1,y2 and y3 such that β(y1) < a ′, b′ < α(y2) and a ′ < β(y3) with α(y3) < b ′. This completes the proof. � 78 PRASAD AND KRUSHNA Theorem 4.3. Let k be an arbitrary positive integer. Assume that there exist numbers ar(r = 1, 2, · · ·,k) and bs(s = 1, 2, · · ·,k − 1) with 0 < a1 < b1 < b1ξ < a2 < b2 < b2 ξ < · · · < ak−1 < bk−1 < bk−1 ξ < ak such that f satisfies the following conditions: (C4) f(t,y(t)) < φp ( arK ) , t ∈ [0, 1] and y ∈ [ξar,ar],r = 1, 2, · · ·,k, (C5) f(t,y(t)) > φp ( bsL ) , t ∈ I and y ∈ [ bs, bs ξ ] ,s = 1, 2, · · ·,k − 1. Then the p-Laplacian fractional order BVP (1.1)-(1.2) has at least 2k − 1 positive solutions in Pak. Proof. We use induction on k. First, for k = 1, we know from the condition (C4) that T : Pa1 → Pa1, then it follows from the Schauder fixed point theorem that the p-Laplacian fractional order BVP (1.1)-(1.2) has at least one positive solution in Pa1. Next, we assume that this conclusion holds for k = l. In order to prove that this conclusion holds for k = l + 1. We suppose that there exist numbers ar(r = 1, 2, · · ·, l + 1) and bs(s = 1, 2, · · ·, l) with 0 < a1 < b1 < b1ξ < a2 < b2 < b2 ξ < · · · < al < bl < blξ < al+1 such that f satisfies the following conditions: (4.3) f(t,y(t)) < φp ( arK ) , t ∈ [0, 1] and y ∈ [ξar,ar],r = 1, 2, · · ·, l + 1, (4.4) f(t,y(t)) > φp ( bsL ) , t ∈ I and y ∈ [ bs, bs ξ ] ,s = 1, 2, · · ·, l. By assumption, the fractional order BVP (1.1)-(1.2) has at least 2l − 1 positive solutions y∗i (i = 1, 2, · · ·, 2l− 1) in Pal. At the same time, it follows from Theorem 4.2, (4.3) and (4.4) that the p-Laplacian fractional order BVP (1.1)-(1.2) has at least three positive solutions y1, y2 and y3 in Pal+1 such that β(y1) < al, bl < α(y2) and al < β(y3) with α(y3) < bl. Obviously y2 and y3 are distinct from y ∗ i (i = 1, 2, · · ·, 2l− 1) in Pal. Therefore, the p-Laplacian fractional order BVP (1.1)-(1.2) has at least 2l + 1 positive solutions in Pal+1, which shows that this conclusion also holds for k = l + 1. This completes the proof. � 5. Examples In this section, as an application, the results of the previous sections are demon- strated with examples. Example 5.1 Consider the p-Laplacian fractional order BVP, (5.1) D1.70+ ( φp ( D2.60+ y(t) )) = f(t,y(t)), t ∈ (0, 1), (5.2) y(0) = y′(0) = y′′(1) = 0,φp ( D2.60+ y(0) ) = 0 = D0.60+ ( φp ( D2.60+ y(1) )) , where f(t,y) = y2(650 − 649e−3y) 5 . p-LAPLACIAN FRACTIONAL ORDER BOUNDARY VALUE PROBLEMS 79 Then the Green’s function G(t,s) for the homogeneous BVP, −D2.60+ y(t) = 0, t ∈ (0, 1), y(0) = y′(0) = y′′(1) = 0, and is given by G(t,s) = { t1.6(1−s)−0.6 Γ(2.6) , t ≤ s, t1.6(1−s)−0.6−(t−s)1.6 Γ(2.6) , s ≤ t. The Green’s function H(t,s) for the BVP, −D1.70+ ( φp ( D2.60+ y(t) )) = 0, t ∈ (0, 1), φp ( D2.60+ y(0) ) = 0 = D0.60+ ( φp ( D2.60+ y(1) )) , and is given by H(t,s) = { t0.7(1−s)0.1 Γ(1.7) , t ≤ s, t0.7(1−s)0.1−(t−s)0.7 Γ(1.7) , s ≤ t. Clearly, the Green functions G(t,s) and H(t,s) are positive. Let p = 2. By direct calculations, ξ = 0.1088, K = 1.0077, L = 27.1209, f0 = 0 and f∞ = ∞. Then, all the conditions of Theorem 3.2 are satisfied. Thus by Theorem 3.2, the p-Laplacian fractional order BVP (5.1)-(5.2) has at least one positive solution. Example 5.2 Consider the p-Laplacian fractional order BVP, (5.3) D1.80+ ( φp ( D2.70+ y(t) )) = f(t,y(t)), t ∈ (0, 1), (5.4) y(0) = y′(0) = y′′(1) = 0,φp ( D2.70+ y(0) ) = 0 = D0.70+ ( φp ( D2.70+ y(1) )) , where f(t,y) = { t 100 + 15 32 y7, 0 ≤ y ≤ 2, y + t 100 + 116 2 , y > 2. Then the Green’s function G(t,s) for the homogeneous BVP, −D2.70+ y(t) = 0, t ∈ (0, 1), y(0) = y′(0) = y′′(1) = 0, and is given by G(t,s) = { t1.7(1−s)−0.7 Γ(2.7) , t ≤ s, t1.7(1−s)−0.7−(t−s)1.7 Γ(2.7) , s ≤ t, The Green’s function H(t,s) for the BVP, −D1.80+ ( φp ( D2.70+ y(t) )) = 0, t ∈ (0, 1), φp ( D2.70+ y(0) ) = 0 = D0.70+ ( φp ( D2.70+ y(1) )) , and is given by H(t,s) = { t0.8(1−s)0.1 Γ(1.8) , t ≤ s, t0.8(1−s)0.1−(t−s)0.8 Γ(1.8) , s ≤ t. 80 PRASAD AND KRUSHNA Clearly, the Green functions G(t,s) and H(t,s) are positive and f is continuous and increasing on [0,∞). Let p = 2. By direct calculations, ξ = 0.0947, K = 1.8901 and L = 29.6238. Choosing a′ = 1,b′ = 2 and c′ = 100, then 0 < a′ < b′ < b ′ ξ ≤ c′ and f satisfies (i) f(t,y) < 1.8901 = φp ( a′K ) , t ∈ [0, 1] and y ∈ [0.0947, 1], (ii) f(t,y) > 59.25 = φp ( b′L ) , t ∈ [1 4 , 3 4 ] and y ∈ [2, 21.12], (iii) f(t,y) < 189.01 = φp ( c′K ) , t ∈ [0, 1] and y ∈ [0, 100]. Then, all the conditions of Theorem 4.2 are satisfied. 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Krushna, Eigenvalues for iterative systems of Sturm-Liouville fractional order two-point boundary value problems, Fract. Calc. Appl. Anal., Vol. 17, No.3(2014), 638–653, DOI: 10.2478/s13540-014-0190-4. [23] C. Yang and J. Yan, Positive solutions for third-order Sturm-Liouville boundary value prob- lems with p-Laplacian, Comput. Math. Appl., 59(2010), 2059–2066. 1Department of Applied Mathematics, Andhra University, Visakhapatnam, 530 003, India, 2Department of Mathematics, MVGR College of Engineering, Vizianagaram, 535 005, India, ∗Corresponding author