Hindawi Publishing Corporation Abstract and Applied Analysis Volume 2013, Article ID 942831, 8 pages http://dx.doi.org/10.1155/2013/942831 Research Article Bifurcation of Positive Solutions for a Class of Boundary Value Problems of Fractional Differential Inclusions Yansheng Liu and Huimin Yu Department of Mathematics, Shandong Normal University, Jinan 250014, China Correspondence should be addressed to Yansheng Liu; yanshliu@gmail.com Received 11 January 2013; Revised 27 February 2013; Accepted 4 March 2013 Academic Editor: Bashir Ahmad Copyright © 2013 Y. Liu and H. Yu. 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. Using Krein-Rutman theorem, topological degree theory, and bifurcation techniques, this paper investigates the existence of positive solutions for a class of boundary value problems of fractional differential inclusions. 1. Introduction Fractional differential equations have been of great interest recently. Engineers and scientists have developed new models that involve fractional differential equations. These models have been applied successfully, for example, in mechanics (theory of viscoelasticity and viscoplasticity), (bio)chemistry (modelling of polymers and proteins), electrical engineering (transmission of ultrasound waves), medicine (modelling of human tissue under mechanical loads), and so forth. For details, see [1–7] and references therein. For example, in [5], Qiu and Bai considered the existence of positive solutions to BVP of the nonlinear fractional differential equation πΆ π·0πΌ+ π’ (π‘) + π (π‘, π’ (π‘)) = 0, 0 < π‘ < 1, π’ (0) = π’σΈ (1) = π’σΈ σΈ (0) = 0, (1) π·0πΌ+ π’ (π‘) + ππ (π‘, π’ (π‘)) = 0, π’(π) (0) = 0, 0 < π‘ < 1, 0 ≤ π ≤ π − 1, π =ΜΈ 2, π’σΈ σΈ (1) = 0, πΆ π·0πΌ+ π’ (π‘) ∈ −πΉ (π‘, π’ (π‘)) , π’(π) (0) = 0, (2) 0 < π‘ < 1, 0 ≤ π ≤ π − 1, π =ΜΈ 2, (3) π’σΈ σΈ (1) = 0, πΆ where 2 < πΌ ≤ 3, π : (0, 1] × [0, +∞) → [0, +∞), and πΆ πΌ π·0+ is the Caputo’s fractional derivatives. They obtained the existence of at least one positive solution by using Krasnoselskii’s fixed point theorem and nonlinear alternative of Leray-Schauder type in a cone. In [8], Tian and Liu investigated the following singular fractional boundary value problem (BVP, for short) of the form πΆ where π − 1 < πΌ ≤ π, π ≥ 4, and π : (0, 1) × (0, +∞) → [0, +∞) is continuous; that is, π(π‘, π’) may be singular at π‘ = 0, 1 and π’ = 0. By constructing a special cone, under some suitable assumptions, they obtained that there exist positive numbers π∗ and π∗∗ with π∗ < π∗∗ such that the above system has at least two positive solutions for π ∈ (0, π∗ ) and no solution for π > π∗∗ . In this paper, we consider the following boundary value problem of fractional differential inclusions of the form where π − 1 < πΌ ≤ π, π ≥ 4, π·0πΌ+ is the Caputo’s fractional + derivatives, and πΉ : π½ × R+ → 2R . As mentioned in [9], the field of differential inclusions is a versatile and general area of mathematics that provides a framework for modelling physical processes that feature discontinuities. Examples of such phenomena include mechanical systems with Coulomb friction modeled as a force proportional to the sign of a velocity and systems whose control laws have discontinuities [10]. In addition, differential inclusions are a useful format for treating differential equations where the right-hand side may be inaccurately known [11]. Differential inclusions are also employed in the dynamic modelling of economic processes and game theory [12], control theory, optimization, partial differential equations, 2 Abstract and Applied Analysis and the study of general evolution processes [13]. The types of the aforementioned applications naturally motivate a deeper theoretical analysis of the subject. Also there are some papers concerned with initial or boundary value problems of fractional differential inclusions (see, for instance, [9, 14–20] and references therein). The method used in these references is fixed point theorem. However, to the best of our knowledge, there is no paper studying such problems using bifurcation ideas. As we know, the bifurcation technique is widely used in solving boundary value problems (see, for instance, [21–24] and references therein). The purpose of present paper is to fill this gap. By using Krein-Rutman theorem, topological degree theory, and bifurcation techniques, the existence of positive solutions of BVP (3) is investigated. The paper is organized as follows. Section 2 contains some preliminaries. In Section 3, by using bifurcation techniques, Krein-Rutman theorem, and topological degree theory, bifurcation results from infinity and trivial solution are established. Finally, in Section 4, the main results of the present paper are given and proved. 2. Preliminaries For convenience, we present some necessary definitions and results from fractional calculus theory (see [6]). Definition 1. The fractional (arbitrary) order integral of the function β ∈ πΏ1 ([π, π]) of order πΌ ∈ R+ is defined by πΌππΌ β (π‘) = ∫ π‘ π πΌ−1 (π‘ − π ) β (π ) dπ , Γ (πΌ) (4) where Γ is the gamma function. When π = 0, we write πΌπΌ β(π‘) = [β ∗ ππΌ ](π‘), where ππΌ (π‘) = π‘πΌ−1 /Γ(πΌ) for π‘ > 0, and ππΌ (π‘) = 0 for π‘ ≤ 0 and ππΌ → πΏ(π‘) as πΌ → 0, where πΏ is the delta function. Definition 2. For a function β given on the interval [π, π], the πΌth Caputo fractional-order derivative of β is defined by ( πΆ πΌ π·π+ π‘ 1 β) (π‘) = ∫ (π‘ − π )π−πΌ−1 β(π) (π ) dπ . Γ (π − πΌ) π (5) Here π is the smallest integer greater than or equal πΌ. π·0πΌ+ π’ (π‘) = 0 (6) 2 π−1 has solutions π’(π‘) = π0 + π1 π‘ + π2 π‘ + ⋅ ⋅ ⋅ + ππ−1 π‘ , for some ππ ∈ R, π = 0, 1, 2, . . . , π − 1, where π is the smallest integer greater than or equal to πΌ. Lemma 4. Assume that π’ ∈ πΆ(0, 1)∩πΏ1 [0, 1] with a derivative of order π that belongs to πΆ(0, 1) ∩ πΏ1 [0, 1]. Then πΆ πΌ0πΌ+ π·0πΌ+ π’ (π‘) 2 π½ πΌ+π½ πΌ0πΌ+ πΌ0+ π = πΌ0+ π (8) is valid in the following case: Re π½ > 0, Re (πΌ + π½) > 0, π ∈ πΏ1 [π, π] . (9) For more detailed results of fractional calculus, we refer the reader to [6]. In addition, we need the following preliminaries on multivalued operators. Let (π, β ⋅ β) be a Banach space. Then a multivalued map Θ : π → 2π is convex (closed) valued if Θ(π₯) is convex (closed) for all π₯ ∈ π. Θ is bounded if Θ(π΅) = βπ₯∈π΅ Θ(π₯) is bounded in π for any bounded set π΅ of π. Θ : π· → 2π is said to be lower semicontinuous, l.s.c. for short, if Θ−1 (π) is open in π· whenever π ⊂ π is open. Let Θ : π· → 2π be a multivalued map and π : π· → π a single-valued function; if for all π₯ ∈ π·, π(π₯) ∈ Θ(π₯), then π is called a selection function of Θ. If in addition π is continuous, then π is called a continuous selection. The following lemmas are crucial in the proof of our main result. Lemma 6. [25, Lemma 2.1, page 14]. Let π· =ΜΈ 0 be a subset of a Banach space π, and Θ : π· → 2π a l.s.c. with closed convex values. Then, given (π€0 , π₯0 ) ∈ ππππβ(Θ), Θ has a continuous selection π such that π(π€0 ) = π₯0 . For more details on multivalued maps, see the books of Deimling [25]. Finally in this section, we list the following results on topological degree of completely operators. Lemma 7 (Schmitt and Thompson [26]). Let π be a real reflexive Banach space. Let πΊ : R × π to π be completely continuous such that πΊ(π, 0) = 0, ππππππ π ∈ R. Let π, π ∈ R (π < π) be such that π’ = 0 is an isolated solution of the equation π’ − πΊ (π, π’) = 0, π’ ∈ π, (10) for π = π and π = π, where (π, 0), (π, 0) are not bifurcation points of (10). Furthermore, assume that deg (πΌ − πΊ (π, ⋅) , π΅π (0) , 0) =ΜΈ deg (πΌ − πΊ (π, ⋅) , π΅π (0) , 0) , (11) Lemma 3. Let πΌ > 0, then the differential equation πΆ Lemma 5. The relation π−1 = π’ (π‘) + π0 + π1 π‘ + π2 π‘ + ⋅ ⋅ ⋅ + ππ−1 π‘ . (7) for some ππ ∈ R, π = 0, 1, 2, . . . , π − 1, where π is the smallest integer greater than or equal πΌ. where π΅π (0) is an isolating neighborhood of the trivial solution. Let T = {(π, π’) : (π, π’) ππ π π πππ’π‘πππ ππ (2.1) π€ππ‘β π’ =ΜΈ 0} ∪ ([π, π] × 0) . (12) Then there exists a connected component C of T containing [π, π] × 0 in R × π, and either (i) C is unbounded in R × π or (ii) C ∩ [(R \ [π, π]) × 0] =ΜΈ 0. Abstract and Applied Analysis 3 Lemma 8 (Schmitt [27]). Let π be a real reflexive Banach space. Let πΊ : R × π to π be completely continuous, and let π, π ∈ R (π < π) be such that the solution of (10) is, a priori, bounded in π for π = π and π = π; that is, there exists an π > 0 such that πΊ (π, π’) =ΜΈ π’ =ΜΈ πΊ (π, π’) We first consider the following linear boundary problem of fractional differential equation: πΆ π·0πΌ+ π’ (π‘) + π (π‘) = 0, π’(π) (0) = 0, (13) for sufficiently large π > 0. Then there exists a closed connected set C of solutions of (10) that is unbounded in [π, π] × π, and either Lemma 10 (Tian and Liu [8]). Given π ∈ πΆ[0, 1], the unique solution of (19) is 1 π’ (π‘) = ∫ πΊ (π‘, π ) π (π ) dπ , (i) C is unbounded in π direction or Lemma 9 (Guo [28]). Let Ω be a bounded open set of infinitedimensional real Banach space πΈ, and let π΄ : Ω → πΈ be completely continuous. Suppose that (i) inf π₯∈πΩ βπ΄π₯β > 0; (ii) π΄π₯ = ππ₯, π₯ ∈ πΩ ⇒ π ∉ (0, 1]. where πΊ (π‘, π ) (πΌ − 1) (πΌ − 2) 2 { π‘ (1 − π )πΌ−3 − (π‘ − π )πΌ−1 , π ≤ π‘; { 1 { 2 = { Γ (πΌ) { { (πΌ − 1) (πΌ − 2) 2 π‘ ≤ π . π‘ (1 − π )πΌ−3 , { 2 (21) (15) (i) πΊ (π‘, π ) > 0, 3. Bifurcation Results 3.1. Assumptions and Conversion of BVP (3). Suppose that the following two assumptions hold throughout the paper. + (H1) Let πΉ : π½ × R+ → 2R be a nonempty, closed and convex multivalued map such that πΉ is l.s.c., where π½ = [0, 1]. (H2) There exist functions π0 , π0 , π∞ , π∞ ∈ πΆ(π½, R+ ) with π0 (π‘), π0 (π‘), π∞ (π‘), π∞ (π‘) ≡ΜΈ 0 in any subinterval of [0, 1] such that πΉ (π‘, π’) (16) ∀π‘, π ∈ [0, 1] ; (ii) πΊ (π‘, π ) ≤ π» (π ) ≤ (1 − π )πΌ−3 , 2Γ (πΌ − 2) π» (π ) (πΌ − 1) (πΌ − 2) 2 { π (1 − π )πΌ−3 − (1 − π )πΌ−1 , π ≤ π‘, { 1 { 2 = { Γ (πΌ) { { (πΌ − 1) (πΌ − 2) 2 π‘ ≤ π ; π (1 − π )πΌ−3 , { 2 (iii) πΊ (π‘, π ) ≥ π‘2 πΊ (π, π ) , ∀π‘, π , π ∈ [0, 1] . (23) ∩ [π∞ (π‘) π’ − π1 (π‘, π’) , π (π‘) π’ + π2 (π‘, π’)] , for all (π‘, π’) ∈ π½ × R+ , where ππ , ππ ∈ πΆ(π½ × R+ ) with ππ (π‘, π’) = π(π’) as π’ → 0 uniformly with respect to π‘ ∈ [0, 1], (π = 1, 2), and ππ (π‘, π’) = π(π’) as π’ → +∞ uniformly with respect to π‘ ∈ [0, 1], (π = 1, 2). The basic space used in this paper is πΆ[0, 1]. Obviously, πΆ[0, 1] is a Banach space with norm βπ’β = maxπ‘∈π½ |π’(π‘)| (for all π’ ∈ πΆ[0, 1]). Let (17) It is easy to see that π is a cone of πΈ. Moreover, from (17), we have for all π’ ∈ π, π’ (π‘) ≥ π‘2 βπ’β , ∀π‘ ∈ π½. (22) where ∞ π := {π’ ∈ πΆ [π½, R+ ] : π’ (π‘) ≥ π‘2 π’ (π ) , ∀π‘, π ∈ π½} . (20) Lemma 11 (Tian and Liu [8]). The function πΊ(π‘, π ) defined by (21) has the following properties: Then ⊂ [π0 (π‘) π’ − π1 (π‘, π’) , π0 (π‘) π’ + π2 (π‘, π’)] (19) where π ∈ πΆ[0, 1]. 0 (ii) there exists an interval [π, π] such that (π, π)∩(π, π) = 0 and C bifurcates from infinity in [π, π] × π. deg (πΌ − π΄, Ω, π) = 0. 0 ≤ π ≤ π − 1, π =ΜΈ 2, π’σΈ σΈ (1) = 0, for all π’ with βπ’β ≥ π . Furthermore, assume that deg (πΌ − πΊ (π, ⋅) , π΅π (0) , 0) =ΜΈ deg (πΌ − πΊ (π, ⋅) , π΅π (0) , 0) , (14) 0 < π‘ < 1, (18) For the sake of using bifurcation technique to investigate BVP (3), we study the following fractional boundary value problem with parameters: πΆ π·0πΌ+ π’ (π‘) ∈ −ππΉ (π‘, π’ (π‘)) , π’(π) (0) = 0, 0 < π‘ < 1, 0 ≤ π ≤ π − 1, π =ΜΈ 2, (24) π’σΈ σΈ (1) = 0. A function (π, π’) is said to be a solution of BVP (24) if (π, π’) satisfies (24). In addition, if π > 0, π’(π‘) > 0 for π‘ ∈ (0, 1), then (π, π’) is said to be a positive solution of BVP (24). Obviously, if π > 0, π’ ∈ π \ {π} is a solution of BVP (24), then 4 Abstract and Applied Analysis by (18) we know that (π, π’) is a positive solution of BVP (24), where π denotes the zero element of Banach space πΈ. For π ∈ πΆ(π½, R+ ) with π(π‘) ≡ΜΈ 0 in any subinterval of π½, define the linear operator πΏ π : πΆ(π½) → πΆ(π½) by 1 πΏ π π’ (π‘) = ∫ πΊ (π‘, π ) π (π ) π’ (π ) dπ , 0 (25) where πΊ(π‘, π ) is defined by (21). From Lemmas 10, 11, and the well-known Krein-Rutman Theorem, one can obtain the following lemma. Lemma 12. The operator defined by (25) has a unique characteristic value π 1 (π), which is positive, real, and simple and the corresponding eigenfunction π(π‘) is of one sign in (0, 1); that is, we have π(π‘) = π 1 (π)πΏ π π(π‘). Notice that the operator πΏ π can be regarded as πΏ π : πΏ2 [0, 1] → πΏ2 [0, 1]. This together with Lemma 12 guarantees that π 1 (π) is also the characteristic value of πΏ∗π , where πΏ∗π is the conjugate operator of πΏ π . Let π∗ denote the nonnegative eigenfunction of πΏ∗π corresponding to π 1 (π). Then we have ∗ π (π‘) = π 1 (π) πΏ∗π π∗ (π‘) , ∀π‘ ∈ π½. π·0πΌ+ π’ (π‘) + ππ (π‘, π’ (π‘)) = 0, π’(π) (0) = 0, Lemma 14. Let [π, π] ⊂ R+ be a compact interval with [π 1 (π∞ ), π 1 (π∞ )] ∩ [π, π] = 0. Then there exists π 1 > 0 such that π’ =ΜΈ π΄ π π’, (27) π (π‘, π’) ∈ [π∞ (π‘) π’ − π1 (π‘, π’) , π∞ (π‘) π’ + π2 (π‘, π’)] , ∀ (π‘, π’) ∈ π½ × R+ . + (π‘, π’) ∈ π½ × R , (π‘, π’) ∈ π½ × (−∞, 0) . (28) Then π(π‘, π’) ≥ 0 on π½ × R. From Lemma 10, the solution of πΆ π·0πΌ+ π’ (π‘) + ππ (π‘, π’ (π‘)) = 0, π’(π) (0) = 0, 0 < π‘ < 1, 0 ≤ π ≤ π − 1, π =ΜΈ 2, 1 Vπ (π‘) ≤ ππ ∫ πΊ (π‘, π ) (π∞ (π ) Vπ (π ) + 0 1 Vπ (π‘) ≥ ππ ∫ πΊ (π‘, π ) (π∞ (π ) Vπ (π ) − π’σΈ σΈ (1) = 0 is equivalent to the fixed point of operator 1 π΄ π π’ (π‘) = π ∫ πΊ (π‘, π ) π (π , π’ (π )) dπ , 0 π2 (π , π’π (π )) ) dπ , σ΅©σ΅© σ΅©σ΅© σ΅©σ΅©π’π σ΅©σ΅© (33) π1 (π , π’π (π )) ) dπ . σ΅©σ΅© σ΅©σ΅© σ΅©σ΅©π’π σ΅©σ΅© (34) Let π∗ and π∗ be the positive eigenfunctions of πΏ∗π∞ , πΏ∗π∞ corresponding to π 1 (π∞ ) and π 1 (π∞ ), respectively. Then from (33), it follows that β¨Vπ , π∗ β© ≤ ππ β¨πΏ π∞ Vπ , π∗ β© (29) ∀π’ ∈ πΆ [0, 1] . (30) 1 (35) 1 π (π , π’ (π )) dπ dπ‘. + ππ ∫ π∗ (π‘) ∫ πΊ (π‘, π ) 2 σ΅©σ΅© πσ΅©σ΅© 0 0 σ΅©σ΅©π’π σ΅©σ΅© Letting π → +∞ and using condition (H2), we have β¨V, π∗ β© ≤ π β¨πΏ π∞ V, π∗ β© = π β¨V, πΏ∗π∞ π∗ β© = π β¨V, + Let Σ ⊂ R × πΆ[0, 1] be the closure of the set of positive solutions of BVP (27). From Lemma 11 and the definitions of π and the cone π, it is easy to see Σ ⊂ π and π΄ π : πΆ[0, 1] → π. Moreover, we have the following conclusion. Lemma 13. For π > 0, (π, π’) is a positive solution of BVP (27) if and only if (π, π’) is a nontrivial solution of BVP (29); that is, π’ is a nontrivial fixed point of operator π΄ π in π. Therefore, the closure of the set of nontrivial solutions (π, π’) of BVP (29) in R+ × π is exactly Σ. (32) Therefore, by virtue of (30), we know 0 Define (31) Proof. Suppose, on the contrary, that there exist {(ππ , π’π )} ⊂ [π, π] × πΆ[0, 1] with βπ’π β → ∞(π → +∞) such that π’π = π΄ ππ π’π . Without loss of generality, assume ππ → π ∈ [π, π]. Notice that π’π ∈ π. By Lemma 13, (17), and (18), we have π’π (π‘) > 0 in (0, 1]. Set Vπ = π’π /βπ’π β. Then Vπ = π΄ ππ π’π /βπ’π β. From the continuity of π(π‘, π’), it is easy to see that {Vπ } is relatively compact in πΆ[0, 1]. Taking a subsequence and relabeling if necessary, suppose Vπ → V in πΆ[0, 1]. Then βVβ = 1 and V ∈ π. On the other hand, from (H2) we know 0 < π‘ < 1, 0 ≤ π ≤ π − 1, π =ΜΈ 2, π (π‘, π’) , π (π‘, 0) , ∀π’ ∈ πΆ [0, 1] π€ππ‘β βπ’β ≥ π 1 . π’σΈ σΈ (1) = 0. π (π‘, π’) = { ∀π ∈ [π, π] , (26) Note that condition (H1) implies that πΉ(π‘, π’) is lower semicontinuous. Then, from Lemma 6, there exists a continuous function π : π½×R+ → R+ such that π(π‘, π’) ∈ πΉ(π‘, π’) for all (π‘, π’) ∈ π½ × R+ . Therefore, to solve BVP (24), we consider the problem πΆ 3.2. Bifurcation from Infinity and Trivial Solution π∗ β©, π 1 (π∞ ) (36) which implies π ≥ π 1 (π∞ ). Similarly, one can deduce from (34) that π ≤ π 1 (π∞ ). To sum up, π 1 (π∞ ) ≤ π ≤ π 1 (π∞ ), which contradicts with π ∈ [π, π]. The conclusion of this lemma follows. Lemma 15. For π ∈ (0, π 1 (π∞ )), there exists π 1 > 0 such that deg (πΌ − π΄ π , π΅π , 0) = 1, ∀π ≥ π 1 . (37) Abstract and Applied Analysis 5 Proof. Notice that [0, π] ∩ [π 1 (π∞ ), π 1 (π∞ )] = 0. From Lemma 14, there exists π 1 > 0 such that π’ =ΜΈ π΄ π π’, ∀π ∈ [0, π] , ∀π’ ∈ πΆ [0, 1] with βπ’β ≥ π 1 , (38) (0, 1] and it is reasonable to suppose Vπ → V (relabeling if necessary) in πΆ[0, 1]. By virtue of (32), we know β¨Vπ , π∗ β© ≥ β¨ππ Vπ , π∗ β© 1 = σ΅©σ΅© σ΅©σ΅© β¨π΄ π π’π , π∗ β© σ΅©σ΅©π’π σ΅©σ΅© which means π’ =ΜΈ ππ΄ π π’, ∀π ∈ [0, 1] , ∀π’ ∈ πΆ [0, 1] with βπ’β ≥ π 1 . (39) Therefore, by the homotopy invariance of topological degree, we have deg (πΌ − π΄ π , π΅π , 0) = deg (πΌ, π΅π , 0) = 1, ∀π ≥ π 1 . (40) Lemma 16. For π > π 1 (π∞ ), there exists π 2 > 0 such that deg (πΌ − π΄ π , π΅π , 0) = 0, ∀π ≥ π 2 . (41) Proof. We first prove that for π > π 1 (π∞ ), there exists π 2 > 0 such that π΄ π π’ =ΜΈ ππ’, ∀π ∈ (0, 1] , ∀π’ ∈ πΆ [0, 1] with βπ’β ≥ π 2 . (42) Suppose, on the contrary, that there exist {(ππ , π’π )} ⊂ (0, 1] × πΆ[0, 1] with βπ’π β → ∞ (π → +∞) such that π΄ π π’π = ππ π’π . By Lemma 13, π’π (π‘) > 0 in (0, 1]. Set Vπ = π’π /βπ’π β; that is, ππ Vπ = π΄ π π’π /βπ’π β. Without loss of generality, assume ππ → π ∈ [0, 1]. First we show π =ΜΈ 0. From (32) and the continuity of π(π‘, π’), it is easy to see that π΄ π π’π /βπ’π β is relatively compact in πΆ[0, 1]. Suppose (π΄ π π’π /βπ’π β) → π¦. Notice that Vπ ∈ π and βVπ β = 1. Therefore, Vπ (π‘) ≥ π‘2 for π‘ ∈ (0, 1]. Consequently, ππ Vπ (π‘) = π΄ π π’π (π‘) σ΅©σ΅© σ΅©σ΅© σ΅©σ΅©π’π σ΅©σ΅© 1 ≥ π ∫ πΊ (π‘, π ) (π∞ (π ) Vπ (π ) − 0 π1 (π , π’π (π )) ) dπ σ΅©σ΅© σ΅©σ΅© σ΅©σ΅©π’π σ΅©σ΅© (43) 1 ≥ ππ‘2 max ∫ π 2 πΊ (π, π ) π∞ (π ) dπ π∈π½ 1 0 − π ∫ πΊ (π‘, π ) 0 π1 (π , π’π (π )) dπ . σ΅©σ΅© σ΅©σ΅© σ΅©σ΅©π’π σ΅©σ΅© From (H2) and Lemma 11, it is easy to see maxπ∈π½ 1 (44) ≥ π β¨πΏ π∞ Vπ , π∗ β© ∫0 π 2 πΊ(π, π )π∞ (π )dπ > 0. If π = 0, letting π → +∞ in the above inequality, we can obtain a contradiction. So π ∈ 1 1 0 0 − π ∫ π∗ (π‘) ∫ πΊ (π‘, π ) π1 (π , π’π (π )) dπ dπ‘. σ΅©σ΅© σ΅©σ΅© σ΅©σ΅©π’π σ΅©σ΅© Letting π → +∞ and using condition (H2), we obtain that β¨V, π∗ β© ≥ π β¨πΏ π∞ V, π∗ β© = π β¨V, πΏ∗π∞ π∗ β© = π β¨V, π∗ β©, π 1 (π∞ ) (45) which implies π ≤ π 1 (π∞ ). This is a contradiction. Therefore, (42) holds. By Lemma 9, for each π > π 1 (π∞ ), there exists π 2 > 0 such that deg (πΌ − π΄ π , π΅π , 0) = 0, ∀π ≥ π 2 . (46) The conclusion of this lemma follows. Theorem 17. [π 1 (π∞ ), π 1 (π∞ )] is a bifurcation interval of positive solutions from infinity for BVP (27), and there exists no bifurcation interval of positive solutions from infinity which is disjoint with [π 1 (π∞ ), π 1 (π∞ )]. More precisely, there exists an unbounded component C∞ of solutions of BVP (27) which meets [π 1 (π∞ ), π 1 (π∞ )] × ∞ and is unbounded in π direction. Proof. From Lemma 13, we need only to prove that the conclusion holds for (29). For fixed π ∈ N with π 1 (π∞ ) − 1/π > 0, by Lemmas 15, 16, and their proof, there exists π > 0 such that all of the conditions of Lemma 8 are satisfied with πΊ(π, π’) = π΄ π π’, π = π 1 (π∞ ) − 1/π, and π = π 1 (π∞ ) + 1/π. So, there exists a closed connected set Cπ of solutions of (29), which is unbounded in [π 1 (π∞ ) − 1/π, π 1 (π∞ ) + 1/π] × πΆ[0, 1]. From Lemma 14, the case (ii) of Lemma 8 cannot occur. Thus, Cπ bifurcates from infinity in [π 1 (π∞ ) − 1/π, π 1 (π∞ ) + 1/π] × πΆ[0, 1] and is unbounded in π direction. In addition, for any closed interval [π, π] ⊂ [π 1 (π∞ ) − 1/π, π 1 (π∞ ) + 1/π] \ [π 1 (π∞ ), π 1 (π∞ )], by Lemma 14, the set {π’ ∈ πΆ[0, 1] : (π, π’) ∈ Σ, π ∈ [π, π]} is bounded in πΆ[0, 1]. Therefore, Cπ must be bifurcated from infinity in [π 1 (π∞ ), π 1 (π∞ )] × πΆ[0, 1], which implies that Cπ can be regarded as C∞ . Consequently, C∞ is unbounded in π direction. By a process similar to the above, one can obtain the following conclusions. Lemma 18. Let [π, π] ⊂ R+ be a compact interval with [π 1 (π0 ), π 1 (π0 )] ∩ [π, π] = 0. Then there exists πΏ1 > 0 such that π’ =ΜΈ π΄ π π’, ∀π ∈ [π, π] , ∀π’ ∈ πΆ [0, 1] with 0 < βπ’β ≤ πΏ1 . (47) 6 Abstract and Applied Analysis Lemma 19. For π ∈ (0, π 1 (π0 )), there exists πΏ1 > 0 such that deg (πΌ − π΄ π , π΅πΏ , 0) = 1, ∀πΏ ∈ (0, πΏ1 ] . (48) Lemma 20. For π > π 1 (π0 ), there exists πΏ2 > 0 such that deg (πΌ − π΄ π , π΅πΏ , 0) = 0, ∀πΏ ∈ (0, πΏ2 ] . (49) Finally, using Lemmas 18–20, Lemma 7, and the similar method used in the proof of Theorem 17, the following conclusion can be proved. interval of positive solutions from the trivial solution, which is disjointed with [π 1 (π0 ), π 1 (π0 )]. We show that C0 must cross the hyperplane {1} × πΆ(π½). Suppose, on the contrary, C0 ∩ {1} × πΆ(π½) = 0. From π 1 (π0 ) < 1, we know C0 ⊂ [0, 1] × πΆ(π½). Notice that C0 is unbounded. Then C0 must joint [0, 1] × {∞}. By Theorem 17, it is a contradiction with π 1 (π∞ ) > 1. Thus the result follows. Theorem 23. Suppose that (H1), (H2), and the following assumption holds. (H3) There exist π > 0 and β ∈ πΏ[0, 1] such that for π‘ ∈ π½, 0 Theorem 21. [π 1 (π ), π 1 (π0 )] is a bifurcation interval of positive solutions from the trivial solution for BVP (27); that is, there exists an unbounded component C0 of positive solutions of BVP (27), which meets [π 1 (π0 ), π 1 (π0 )] × {0}. Moreover, there exists no bifurcation interval of positive solutions from the trivial solution which is disjointed with [π 1 (π0 ), π 1 (π0 )]. 1 sup πΉ (π‘, π’) ≤ β (π‘) , max ∫ πΊ (π‘, π ) β (π ) dπ < π . π‘∈π½ π‘2 π ≤π’≤π (50) In addition, suppose π 1 (π0 ) < 1, 4. Main Results The main results of this paper are the following two conclusions. Theorem 22. Suppose that (H1) and (H2) hold. In addition, suppose either (i) π 1 (π∞ ) < 1 < π 1 (π0 ) or (ii) π 1 (π0 ) < 1 < π 1 (π∞ ). Then BVP (3) has at least one positive solution. Proof. We need only to prove that there is a component of Σ that crosses the hyperplane {1} × πΆ(π½), where Σ ⊂ R+ ×πΆ[0, 1] is the closure of the set of positive solutions of BVP (27). Notice that (0, 0) is the only solution of (27) with π = 0. By Lemmas 14 and 18, for any component C of Σ, we have C ∩ ({0} × πΆ(π½)) = 0. Case (i). Consider π 1 (π∞ ) < 1 < π 1 (π0 ). From Theorem 17, there exists an unbounded component C∞ of solutions of (27), which meets [π 1 (π∞ ), π 1 (π∞ )] × ∞ and is unbounded in π direction. If C∞ ∩ (R+ × {0}) = 0, by C∞ ∩ ({0} × πΆ(π½)) = 0 and Theorem 17, we know that C∞ must cross the hyperplane {1} × πΆ(π½). If C∞ ∩ (R+ × {0}) =ΜΈ 0, by Theorem 21, we know C∞ ∩ + (R × {0}) ∈ [π 1 (π0 ), π 1 (π0 )] × {0}. Therefore, C∞ joins [π 1 (π0 ), π 1 (π0 )] × {0} to [π 1 (π∞ ), π 1 (π∞ )] × ∞. This together with π 1 (π∞ ) < 1 < π 1 (π0 ) guarantees that C∞ crosses the hyperplane {1} × πΆ(π½). Case (ii). Consider π 1 (π0 ) < 1 < π 1 (π∞ ). From Theorem 21, there exists an unbounded component C0 of positive solutions of BVP (27), which meets [π 1 (π0 ), π 1 (π0 )] × {0}. Moreover, there exists no bifurcation 0 π 1 (π∞ ) < 1. (51) Then BVP (3) has at least two positive solutions. Proof. From Theorems 17 and 21, there exist two unbounded components C0 and C∞ of solutions of (27), which meet [π 1 (π0 ), π 1 (π0 )] × {0} and [π 1 (π∞ ), π 1 (π∞ )] × ∞, respectively. It is sufficient to show that C0 and C∞ are disjoint in [0, 1] × πΆ(π½) and both cross the hyperplane {1} × πΆ(π½). For this sake, from assumption (H3), there exists π > 0 such that 1 (1 + π) max ∫ πΊ (π‘, π ) β (π ) dπ < π . π‘∈π½ 0 (52) Now we show Σ ∩ ([0, 1 + π] × ππ΅π ) = 0, where π΅π = {π’ ∈ πΆ(π½) : βπ’β < π }. Suppose that, on the contrary, (π, π’) is a solution of (27) such that 0 ≤ π ≤ 1 + π and βπ’β = π . Then by Lemma 13, we know π’ ∈ π. Therefore, π’(π‘) ∈ [π‘2 π , π ] for π‘ ∈ π½. From (H3), (30), and Lemma 13, it follows that 1 π = βπ’β = max π ∫ πΊ (π‘, π ) π (π , π’ (π )) dπ π‘∈π½ 0 1 (53) ≤ (1 + π) max ∫ πΊ (π‘, π ) β (π ) dπ < π , π‘∈π½ 0 which is a contradiction. Thus, Σ ∩ ([0, 1 + π] × ππ΅π ) = 0, which implies C0 ∩ ([0, 1 + π] × ππ΅π ) = 0, C∞ ∩ ([0, 1 + π] × ππ΅π ) = 0. (54) Immediately, C0 and C∞ are disjoint in [0, 1] × πΆ(π½). Notice that C0 and C∞ are both unbounded. Moreover, C0 ∩ ({0} × πΆ(π½)) = 0, C∞ ∩ ({0} × πΆ(π½)) = 0, and C∞ is unbounded in π direction. So C0 and C∞ both cross the hyperplane {1}×πΆ(π½). This means that there exist (1, π’1 ) ∈ C0 and (1, π’2 ) ∈ C∞ with βπ’1 β < π and βπ’2 β > π . Consequently, BVP (3) has at least two positive solutions. Abstract and Applied Analysis 7 5. An Example Let π be the unique characteristic value of πΏ 1 corresponding to positive eigenfunctions with π(π‘) ≡ 1 in (25). From Lemma 12 it follows that π exists. Example 24. Consider the following boundary value problem of fractional differential inclusions πΆ π·03.5 + π’ (π‘) ∈ −πΉ (π‘, π’ (π‘)) , π’(π) (0) = 0, 0 < π‘ < 1, 0 ≤ π ≤ 3, π =ΜΈ 2, (55) π’σΈ σΈ (1) = 0, where π π πΉ (π‘, π’) = [ π’ − π (π‘, π’) , π’ + π2 (π‘, π’)] 4 2 ∩ [2ππ’ − π1 (π‘, π’) , 3ππ’ + π (π‘, π’)] , π 2 3 π‘π’, { { {4 π (π‘, π’) = { { {π 2 π‘ √π’, {4 2ππ’, { { π1 (π‘, π’) = { { {2π√π’, π2 (π‘, π’) = π‘ ∈ π½, π’ ∈ [0, 1] , π‘ ∈ π½, π’ ∈ [1, +∞) , (56) π‘ ∈ π½, π’ ∈ [0, 1] , π‘ ∈ π½, π’ ∈ [1, +∞) , 5π π’ + π (π‘, π’) . 2 Then BVP (55) has at least one positive solution. Proof. BVP (55) can be regarded as the form (3). From (56), one can see that (H1) and (H2) are satisfied with π0 (π‘) = π/4, π∞ (π‘) = 2π, π0 (π‘) = π/2, π∞ (π‘) = 3π, and π1 (π‘, π’) = π2 (π‘, π’) = π(π‘, π’). By the definition of π, it is easy to see π 1 (π∞ ) = 1/2 < 1 < 2 = π 1 (π0 ). Therefore, by Theorem 22, BVP (55) has at least one positive solution. 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