International Journal of Analysis and Applications Volume 19, Number 2 (2021), 239-251 URL: https://doi.org/10.28924/2291-8639 DOI: 10.28924/2291-8639-19-2021-239 BOUNDARY VALUE PROBLEMS FOR FRACTIONAL DIFFERENTIAL EQUATION IN SPECIAL BANACH SPACE BEDDANI MOUSTAFA1,∗, HEDIA BENAOUDA2 1Department of Mathematics, Djillali Liabes University of Sidi Bel-Abbés, PO BOX 89 22000 Bel-Abbés, Algeria 2Laboratory of Mathematics, University of Tiaret, PO BOX 78 14000 Tiaret, Algeria ∗Corresponding author: beddani2004@yahoo.fr Abstract. This paper studies the existence of solutions of boundary value problem for fractional differential equations on the half-line in a special Banach space. The main result is based on Mönch fixed point theorem combining with a suitable measure of non-compactness, an example is given to illustrate our approach. 1. Introduction Fractional differential equations play a very important role in describing some real world problems, for example, in the description of hereditary properties of various materials and processes. They are also widely applied in the mathematical modeling of processes in physics, chemistry, aerodynamics, electro-dynamics of complex medium, polymer rheology, etc. Consequently, the fractional calculus and its applications in various fields of science and engineering have received much attention and have developed very rapidly (cf. [18,20,23] for instance). Very recently, many research papers have appeared concerning the fractional differential equations in Banach spaces, some of them investigated the existence results of solutions on finite intervals by classical tools from Received October 16th, 2020; accepted November 11th, 2020; published February 24th, 2021. 2010 Mathematics Subject Classification. 34B15, 34B40, 26A33. Key words and phrases. boundary value problem, measure of non-compactness, unbounded domain, special Banach space, Mönch fixed point theorem, Riemann-Liouville fractional derivative. ©2021 Authors retain the copyrights of their papers, and all open access articles are distributed under the terms of the Creative Commons Attribution License. 239 https://doi.org/10.28924/2291-8639 https://doi.org/10.28924/2291-8639-19-2021-239 Int. J. Anal. Appl. 19 (2) (2021) 240 functional analysis; see, for example References. [1, 3, 6–8, 19, 21, 22]. In [4]. A. Arara and M. Benchohra studied the following problem  cDα 0+ y(t) = f(t,y(t)), t ∈ J = (0, +∞), 1 < α ≤ 2, y(0) = y0, y is bounded on J, where cDα 0+ is the Caputo fractional derivative of order α, f : J × R → R is a is a continuous function and y0 ∈ R. The main approach is based on Schauder’s fixed point theorem. my results is to generalize the previous work. This article concerns the existence of solutions of boundary value problem for fractional differential equations on unbounded interval. We consider the boundary value problem (1.1) Dα0+y(t) = f(t,y(t)), t ∈ J = (0, +∞), (1.2) I2−α 0+ y(0+) = y0, (1.3) Dα−1 0+ y(∞) = y∞. Dα 0+ denote Riemann-Liouville fractional derivative introduced, 1 < α ≤ 2. The operator I2−α 0+ denotes the left-sided Riemann-Liouville fractional integral, the state y(·) takes value in a Banach space E, f : (0,∞) ×E → E will be specified in later sections and (y0,y∞) ∈ E ×E. This paper is organized in the following way. In Section 2, we give some general results and preliminaries and in Section 3, we present existence results for the problem (1.1)-(1.3), using the Mönch’s fixed point theorem combined with the technique of measure of noncompactness. Finally an illustrative example will be presented in Section 4. 2. Preliminary results In this section, we introduce some notation and technical results which are used throughout this paper. Let I ⊂ J be a compact interval and denote by C(I,E) the Banach space of continuous functions y : I → E with the usual norm ‖y‖∞ = sup{‖y(t)‖, t ∈ I}. L1(J,E) the space of E-valued Bochner integrable functions on J with the norm ‖f‖L1 = ∫ +∞ 0 ‖f(t)‖dt. Int. J. Anal. Appl. 19 (2) (2021) 241 We consider the space of functions Cα([0,∞),E) = {y ∈ C(J,E) : lim t→0+ t2−αy(t) exists and finite}. For y ∈ Cα((0,∞),E), we define yα by yα(t) =   t 2−αy(t), t ∈ (0,∞), limt−→0 t 2−αy(t), t = 0. It is clear that yα ∈ C([0,∞),E). We consider the following Banach space Xα([0,∞),E) = {y ∈ Cα([0,∞),E) : lim t→∞ t2−αy(t) 1 + tα exists and finite}. A norm in this space is given by ‖y‖α = sup t∈J t2−α‖y(t)‖ 1 + tα . We begin with some definitions from the theory of fractional calculus. Let α > 0, n = dαe + 1 (the least integer greater than or equal to α) and h ∈ C(J,E). Definition 2.1. [18]. (1) The Riemann-Liouville fractional integral of the function h of order α is defined by Iα0+h(t) = gα(t) ∗h(t) = ∫ t 0 gα(t−s)h(s)ds, t > 0, where ∗ denotes convolution and gα(t) = tα−1/Γ(α). (2) The Riemann-Liouville fractional derivative of the function h of order α is defined by Dα0+h(t) = dn dtn (gn−α(t) ∗h(t)), for all t > 0. Where Γ is the gamma function. For the existence of solutions for the problem (1.1)-(1.3), we need the following auxiliary lemmas. Lemma 2.1. [26] Let α > 0, then the differential equation Dα0+h(t) = 0, has solutions h(t) = c1t α−1 + c2t α−2 + . . . + cnt α−n, for some ci ∈ R, i = 1 . . .n, where n = [α] + 1. Lemma 2.2. [26] Let α > 0, then Iα0+D α 0+h(t) = h(t) + c1t α−1 + c2t α−2 + . . . + cnt α−n, for some ci ∈ R, i = 0, . . . ,n, where n = [α] + 1. Int. J. Anal. Appl. 19 (2) (2021) 242 Remark 2.1. For α > 0, k > −1, we have Iα0+t k = Γ(k + 1) Γ(α + k + 1) tα+k and Dα0+t k = Γ(k + 1) Γ(k −α + 1) tk−α, t > 0, giving in particular Dα0+t α−m = 0, m = 1, . . . ,n, where n is the smallest integer greater than or equal to α. Remark 2.2. If h is suitabe function (see for instance [18, 20, 23] ), we have the composition relations Dα0+I α 0+h(t) = h(t), α > 0 and D α 0+I k 0+h(t) = I k−α 0+ h(t), k > α > 0, t > 0. We note that γ,γC and γXα the Kuratowski noncompactness measure of bounded sets in the spaces E,C(I,E) and Xα, respectively. As for the definition of the Kuratowski noncompactness measure, we refer to references [5, 17]. The following properties of the Kuratowski measure of noncompactness and Mönch fixed point theorem are needed for our discussion. Lemma 2.3. If H ⊂ C(I,E) is bounded and equicontinuous, then γ(H(t)) is continuous on I and γC(H) = max t∈I γ(H(t)), γ ( { ∫ I x(t)dt : x ∈ H} ) ≤ ∫ I γ(H(t))dt, where H(t) = {x(t) : x ∈ H}. Theorem 2.1. [2, 24] Let D be a bounded, closed and convex subset of a Banach space E such that 0 ∈ D , and let N be a continuous mapping of D into itself. If the implication V = convN(V ) or V = N(V ) ∪{0} =⇒ γ(V ) = 0, holds for every subset V of D, then N has a fixed point. 3. Main result We will need to introduce the following hypotheses which are assumed here after. (H1) There exists a nonnegative functions a,b ∈ C(J,R+) such that ‖f(t,u)‖≤ a(t) + t2−αb(t)‖u‖ for all t ∈ J and u ∈ E, where ∫ ∞ 0 (1 + tα)b(t)dt < Γ(α), ∫ ∞ 0 a(t)dt < ∞. (H2) ∀t ∈ (0,L],∀x,y ∈ E : ‖f(t,x) −f(t,y)‖≤ t 2−α 1+tα ‖x−y‖. (H3) There exists nonnegative function ` ∈ L1(J,R+) such that for each nonempty, bounded set Ω ⊂ Xα(J,E) γ(f(t, Ω(t))) ≤ t2−α`(t)γ(Ω(t)), for all t ∈ J, where ∫ ∞ 0 (1 + tα)`(t)dt ≤ Γ(α). Int. J. Anal. Appl. 19 (2) (2021) 243 Definition 3.1. A function y ∈ Xα([0, +∞)) is said to be solution of the problem (1.1)-(1.3) if y satisfies the equation Dα 0+ y(t) = f(t,y(t)) and the conditions (1.2 − 1.3). Lemma 3.1. Let 1 < α < 2 and let h : J → E be continuous. A function y is a solution of the fractional integral equation (3.1) y(t) = 1 Γ(α) [y∞ − ∫ ∞ 0 h(t)dt]tα−1 + y0 Γ(α− 1) tα−2 + 1 Γ(α) ∫ t 0 (t−s)α−1h(s)ds if and only if y is solution of the problem (3.2) Dα0+y(t) = h(t), t ∈ J = (0, +∞), (3.3) I2−α 0+ y(0+) = y0, (3.4) Dα−1 0+ y(∞) = y∞. Proof. Assume that y satisfies the problem (3.2)-(3.4). We may apply Lemma 2.2 to reduce equation (3.2) to an equivalent integral equation (3.5) y(t) = c1t α−1 + c2t α−2 + Iα0+h(t), for some c1, c2 ∈ R. Applying I2−α0+ to both side of (3.5), we have I2−α 0+ y(t) = c1I 2−α 0+ tα−1 + c2I 2−α 0+ tα−2 + I2−α 0+ Iα0+h(t). From Remark 2.1, we then get I2−α 0+ y(t) = c1Γ(α) Γ(2) t + c2Γ(α− 1) + 1 Γ(2) ∫ t 0 (t−s)h(s)ds. As t −→ 0, we obtain c2 = y0 Γ(α− 1) . Applying Dα−1 0+ to both side of (3.5), we have Dα−1 0+ y(t) = c1D α−1 0+ tα−1 + c2D α−1 0+ tα−2 + Dα−1 0+ Iα0+h(t). From Remark 2.1 and Remark 2.2, we then get Dα−1 0+ y(t) = c1Γ(α) + 1 Γ(1) ∫ t 0 h(s)ds. Int. J. Anal. Appl. 19 (2) (2021) 244 Hence c1 = 1 Γ(α) (y∞ − ∫ ∞ 0 h(t)dt). Thus, we have y(t) = 1 Γ(α) [y∞ − ∫ ∞ 0 h(t)dt]tα−1 + y0 Γ(α− 1) tα−2 + 1 Γ(α) ∫ t 0 (t−s)α−1h(s)ds. Conversely. The proof is simple. � Consider the operator N : Xα([0,∞),E) → Xα([0,∞),E) defined by N(y)(t) = y∞ Γ(α) tα−1 + y0 Γ(α− 1) tα−2 − 1 Γ(α) ∫ t 0 [tα−1 − (t−s)α−1]f(s,y(s))ds − 1 Γ(α) ∫ ∞ t tα−1f(s,y(s))ds. The following several lemmas present some properties of the operator N, which are necessary for the proof of our main result. Lemma 3.2. Suppose that conditions (H1) and (H2) are valid. Then the operator N is bounded and con- tinuous. Proof. For y ∈ Xα([0,∞),E), it is easy to deduce from (H1), and that Ny ∈ Xα(J,E). Furthermore, (H1) guarantees that t2−α‖N(y)(t)‖ 1 + tα ≤ ‖y∞‖ Γ(α) + ‖y0‖ Γ(α− 1) + 1 Γ(α) ∫ ∞ 0 ‖f(s,y(s))‖ds ≤ ‖y∞‖ Γ(α) + ‖y0‖ Γ(α− 1) + ‖y‖α Γ(α) ∫ ∞ 0 (1 + tα)b(t)dt + 1 Γ(α) ∫ ∞ 0 a(t)dt. Hence, N : Xα(J,E) → Xα(J,E) is bounded. Next we prove that N is continuous. Let {yn}∞n=1 ⊂ Xα(J,E) and y ∈ Xα(J,E) such that yn → y as n →∞. Then, {yn}∞n=1 is a bounded set of Xα(J,E), i.e. there exists M > 0 such that ‖yn‖α ≤ M for n > 1. We also have by taking limit that ‖y‖α ≤ M. In view of condition (H1), for any ε > 0, there exists L > 0 such that∫ ∞ L a(t)dt < Γ(α) 6 ε, ∫ ∞ L (1 + tα)b(t)dt < Γ(α)ε 6M ε, and there exists Ñ ∈ N such that, for all n ≥ Ñ, we have ‖f(s,yn(s)) − (s,y(s))‖ < Γ(α) 3L ε. Therefore, for all t ∈ J and n > Ñ, we can obtain from t2−α 1 + tα ‖N(yn)(t) −N(y)(t)‖≤ 1 Γ(α) ∫ t 0 ‖f(s,yn(s)) −f(s,y(s))‖ds + 1 Γ(α) ∫ ∞ t ‖f(s,yn(s)) −f(s,y(s))‖ds. Int. J. Anal. Appl. 19 (2) (2021) 245 If t ≤ L and n > Ñ, we can obtain from t2−α 1 + tα ‖N(yn)(t) −N(y)(t)‖≤ 1 Γ(α) ∫ t 0 ‖f(s,yn(s)) −f(s,y(s))‖ds + 1 Γ(α) ∫ ∞ t ‖f(s,yn(s)) −f(s,y(s))‖ds ≤ 1 Γ(α) ∫ t 0 ‖f(s,yn(s)) −f(s,y(s))‖ds + 1 Γ(α) [∫ L t ‖f(s,yn(s)) −f(s,y(s))‖ds + ∫ ∞ L ‖f(s,yn(s)) −f(s,y(s))‖ds ] ≤ 2 Γ(α) ∫ L 0 ‖f(s,yn(s)) −f(s,y(s))‖ds + 2M Γ(α) ∫ ∞ L (1 + sα)b(s)ds + 2 Γ(α) ∫ ∞ L a(s)ds ≤ ε 3 + ε 3 + ε 3 = ε. The case when t > L and n > Ñ is treated similarly. Thus we conclude that ‖yn −y‖α → 0 as n →∞, namely, N is continuous and the conclusion of the lemma follows. � Lemma 3.3. Let condition (H1) be satisfied and B be a bounded subset of Xα(J,E). Then (i) t2−αN(B)(t) 1+tα is equicontinuous on any compact interval of J. (ii) For given ε > 0, there exists a constant N1 > 0 such that ‖ t 2−α 1 N(y)(t1) 1+tα1 − t 2−α 2 N(y)(t2) 1+tα2 ‖ < ε for any t1, t2 ≥ N1 and y(.) ∈ B. Proof. We have Ny(t) = y∞ − ∫∞ 0 f(t,y(t))dt Γ(α) tα−1 + y0 Γ(α− 1) tα−2 + 1 Γ(α) ∫ t 0 (t−s)α−1f(s,y(s))ds. In view of condition (H1) and the boundedness of B, there exists M > 0 such that (3.6) ∫ ∞ 0 ‖f(t,y(t))‖dt ≤ M for any y ∈ B. Int. J. Anal. Appl. 19 (2) (2021) 246 In order to prove (i), let the constant r be such that ‖y‖α ≤ r for any y ∈ B, and without loss of generality, let [a,b] ⊂ J be a compact interval and t1, t2 ∈ [a,b] with t1 < t2. Then ‖ t2−α1 N(y)(t1) 1 + tα1 − t2−α2 N(y)(t2) 1 + tα2 ‖≤ ‖y∞‖ + M Γ(α) | t1 1 + tα1 − t2 1 + tα2 | + ‖y0‖ Γ(α− 1) ∣∣∣∣ 11 + tα1 − 11 + tα2 ∣∣∣∣ + 1 Γ(α) ∥∥∥∥ ∫ t1 0 (t1 −s)α−1f(s,y(s))ds− ∫ t2 0 (t2 −s)α−1f(s,y(s))ds ∥∥∥∥ ≤ ‖y∞‖ + M Γ(α) | t1 1 + tα1 − t2 1 + tα2 | + ‖y0‖ Γ(α− 1) ∣∣∣∣ 11 + tα1 − 11 + tα2 ∣∣∣∣ + 1 Γ(α) ∫ t1 0 |(t2 −s)α−1 − (t1 −s)α−1|‖f(s,y(s))‖ds + 1 Γ(α) ∫ t2 t1 (t2 −s)α−1‖f(s,y(s))‖ds ≤ ‖y∞‖ + M Γ(α) | t1 1 + tα1 − t2 1 + tα2 | + ‖y0‖ Γ(α− 1) ∣∣∣∣ 11 + tα1 − 11 + tα2 ∣∣∣∣ + 1 Γ(α) ∫ t1 0 |(t2 −s)α−1 − (t1 −s)α−1|a(s)ds + r Γ(α) ∫ t1 0 |(t2 −s)α−1 − (t1 −s)α−1|(1 + sα)b(s)ds + 1 Γ(α) ∫ t2 t1 (t2 −s)α−1a(s)ds + r Γ(α) ∫ t2 t1 (t2 −s)α−1(1 + sα)b(s)ds ≤ ‖y∞‖ + M Γ(α) | t1 1 + tα1 − t2 1 + tα2 | + ‖y0‖ Γ(α− 1) ∣∣∣∣ 11 + tα1 − 11 + tα2 ∣∣∣∣ + a∗ + b∗r Γ(α) (∫ t1 0 (t2 −s)α−1 − (t1 −s)α−1ds ) + a∗ + b∗r Γ(α) ∫ t2 t1 (t2 −s)α−1ds + 2b∗r Γ(α) (∫ t2 0 (t2 −s)α−1sαds− ∫ t1 0 (t1 −s)α−1sαds ) ≤ ‖y∞‖ + M Γ(α) | t1 1 + tα1 − t2 1 + tα2 | + ‖y0‖ Γ(α− 1) ∣∣∣∣ 11 + tα1 − 11 + tα2 ∣∣∣∣ + a∗ + b∗r Γ(1 + α) (tα2 − t α 1 − (t2 − t1) α) + a∗ + b∗r Γ(1 + α) (t2 − t1)α + 2b∗rB(α,α + 1) Γ(α) (t2α2 − t 2α 1 ), where a∗ = maxt∈[a,b] a(t) and b ∗ = maxt∈[a,b] b(t). As t2 → t1 the right-hand side of the above inequality tends to zero. Then t2−αN(B)(t) 1+tα is equicontinuous on [a,b]. Next we verify assertion (ii). Let ε > 0, we heve ‖ t2−α1 N(y)(t1) 1 + tα1 − t2−α2 N(y)(t2) 1 + tα2 ‖≤ ‖y∞‖ + M Γ(α) ∣∣∣∣ t11 + tα1 − t21 + tα2 ∣∣∣∣ + ‖y0‖Γ(α− 1) ∣∣∣∣ 11 + tα1 − 11 + tα2 ∣∣∣∣ + 1 Γ(α) ∥∥∥∥ ∫ t1 0 t2−α1 (t1 −s) α−1 1 + tα1 f(s,y(s))ds− ∫ t2 0 t2−α2 (t2 −s) α−1 1 + tα2 f(s,y(s))ds ∥∥∥∥ . Int. J. Anal. Appl. 19 (2) (2021) 247 It is sufficient to prove that∥∥∥∥ ∫ t1 0 t2−α1 (t1 −s) α−1 1 + tα1 f(s,y(s))ds− ∫ t2 0 t2−α2 (t2 −s) α−1 1 + tα2 f(s,y(s))ds ∥∥∥∥ ≤ ε. Relation (3.6) yields that there exits N0 > 0 such that (3.7) ∫ ∞ N0 ‖f(t,y(t))‖dt ≤ ε 3 for any y ∈ B. On the other hand, since limt→∞ t2−α(t−N0)α−1 1+tα = 0, there exists N1 > N0 such that, for any t1, t2 ≥ N1 and s ∈ [0,N0], we have (3.8) ∣∣∣∣t2−α2 (t2 −s)α−11 + tα2 − t 2−α 1 (t1 −s) α−1 1 + tα1 ∣∣∣∣ < ε3M . Now taking t1, t2 ≥ N1, from (3.7), (3.8) we can arrive at∥∥∥∥ ∫ t1 0 t2−α1 (t1 −s) α−1 1 + tα1 f(s,y(s))ds− ∫ t2 0 t2−α2 (t2 −s) α−1 1 + tα2 f(s,y(s))ds ∥∥∥∥ ≤ ∫ N1 0 ∣∣∣∣t2−α2 (t2 −s)α−11 + tα2 − t 2−α 1 (t1 −s) α−1 1 + tα1 ∣∣∣∣‖f(s,y(s))‖ds + ∫ t1 N1 t2−α1 (t1 −s) α−1 1 + tα1 ‖f(s,y(s))‖ds + ∫ t2 N1 t2−α2 (t2 −s) α−1 1 + tα2 ‖f(s,y(s))‖ds < ε 3M ∫ ∞ 0 ‖f(s,y(s))‖ds + 2 ∫ ∞ N1 ‖f(s,y(s))‖ds < ε. Therefore, we complete the proof of lemma 3.3. � Lemma 3.4. [25] Suppose that condition (H1) holds and B is a bounded subset of Xα(J,E). Then γXα(N(B)) = supt∈J γ ( t2−αN(B)(t) 1+tα ) . Now we are in a position to give the main result of this work. Let B = {y ∈ Xα([0,∞),E) : ‖y‖α ≤ R}. Theorem 3.1. Suppose that conditions (H1), (H2) and (H3) are valid. If (H4) R > ‖y∞‖ + (α− 1)‖y0‖ + ∫∞ 0 a(t)dt Γ(α) − ∫∞ 0 (1 + tα)b(t)dt . Then the problem (1.1)-(1.3) has at least one solution. Proof. First we transform problem (1.1)-(1.3) into a fixed point problem. Consider the operator N : Xα([0,∞),E) → Xα([0,∞),E) defined by N(y)(t) = y∞ Γ(α) tα−1 + y0 Γ(α− 1) tα−2 − 1 Γ(α) ∫ t 0 [tα−1 − (t−s)α−1]f(s,y(s))ds − 1 Γ(α) ∫ ∞ t tα−1f(s,y(s))ds. Int. J. Anal. Appl. 19 (2) (2021) 248 From Lemma 3.1, the fixed points of N are solutions to (1.1)-(1.3). We shall show that N satisfies the assumptions of Mönch fixed point theorem (Theorem 2.1). Then we can derive that N : B → B. Indeed, for any y ∈ B, by condition (H1) we get ‖ t2−αN(y)(t) 1 + tα ‖≤ ‖y∞‖ Γ(α) + ‖y0‖ Γ(α− 1) + 1 Γ(α) ∫ ∞ 0 ‖f(t,y(t))‖dt ≤ (1 Γ(α) ( ‖y∞‖ + (α− 1)‖y0‖ + ∫ ∞ 0 a(t)dt + R ∫ ∞ 0 (1 + tα))b(t)dt ) < R. Hence, from (H4) we have ‖Ny‖α ≤ R, and we conclude that N : B → B. Clearly B is a bounded, convex and closed subset of Xα([0,∞),E), together with Lemma 3.2 we know that N : B → B is continuous. Finally we need to prove the following implication V ⊂ conv{N(V ) ∪{0}} =⇒ γXα(V ) = 0, for any V ⊂ B. Let V ⊂ B such that V ⊂ conv{N(V ) ∪{0}} and t ∈ J, we choose ξ > 0 and n > 0 such that ξ < t < n. For each y ∈ V , we consider Nξ,n(y)(t) = y∞ Γ(α) tα−1 + y0 Γ(α− 1) tα−2 + 1 Γ(α) ∫ t ξ [tα−1 − (t−s)α−1]f(s,y(s))ds + 1 Γ(α) ∫ n t (t−s)α−1f(s,y(s))ds. Then from (H1), we obtain that t2−α 1 + tα ‖Nξ,n(y)(t) −N(y)(t)‖≤ 1 Γ(α) ∫ ξ 0 ‖f(t,y(t))‖dt + 1 Γ(α) ∫ ∞ n ‖f(t,y(t))‖dt ≤ 1 Γ(α) (∫ ξ 0 a(t)dt + R ∫ ξ 0 (1 + tα))b(t)dt + ∫ ∞ n a(t)dt + R ∫ ∞ n (1 + tα))b(t)dt ) , this shows that Hd ( t2−αNξ,n(V )(t) 1+tα , t2−αN(V )(t) 1+tα ) → 0 as ξ → 0 and n → ∞, t ∈ J. Where Hd denotes the Hausdorff metric in space E. By the prorerty of noncompactness mearure we get (3.9) lim ξ→0, n→∞ γ ( t2−αNξ,n(V )(t) 1 + tα ) = γ ( t2−αN(V )(t) 1 + tα ) . From lemma 3.3, the set {t 2−αN(V )(t) 1+tα }⊂ Xα([0,∞),E) is equicontinuous on any compact of J. By (H1), il is easy to know that {f(.,y(.)) : y ∈ V} is equicontinuous on [ξ,n]. Moreover {f(.,y(.)) : y ∈ V} is bounded Int. J. Anal. Appl. 19 (2) (2021) 249 on [ξ,n], by (H1). Using Lemma 2.3, Lemma 3.4 and (H3), we arrive at γ ( t2−αNξ,nV (t) 1 + tα ) ≤ 1 Γ(α) ∫ n ξ (1 + tα)`(t)γ ( t2−αV (t) 1 + tα ) dt ≤ 1 Γ(α) ∫ n ξ (1 + tα)`(t)γ ( t2−αN(V )(t) 1 + tα ) dt ≤ 1 Γ(α) ∫ n ξ (1 + tα)`(t)γXα(N(V ))dt. From (3.9), we know that γ ( t2−αN(V )(t) 1 + tα ) ≤ 1 Γ(α) ∫ ∞ 0 (1 + tα)`(t)γXα(N(V ))dt. Thus γXα(N(V )) ≤ 1 Γ(α) ∫ ∞ 0 (1 + tα)`(t)γXα(N(V ))dt. Consequently, by condition (H3). We get γXα(N(V )) = 0; that is γXα(V ) = 0. From the theorem 2.1, we conclude that N has a fixed point y ∈ B which is a solution of problem (1.1)-(1.3). � 4. Example We consider the following problem. (4.1) D 3 2 y(t) = ( √ tyn(t) (1 + t 3 2 )e10t + 2t) (1 + t2)2 )∞ n=1 , t ∈ J = (0, +∞), (4.2) I 1 2 0+ y(t) = y0, (4.3) D 1 2 0+ y(∞) = y∞. Let E = {(y1, . . . ,yn, . . .) : sup |yn| < ∞}, with the norm ‖y‖ = supn |yn|, then E is a Banach space and problem (4.1)-(4.3) can be regarded as a problem of the form (1.1)-(1.3), with α = 3 2 and f(t,y(t)) = (f(t,y1(t)), . . . ,f(t,yn(t)), . . .), where f(t,yn(t)) = √ tyn(t) (1 + t 3 2 )e10t + 2t (1 + t2)2 ,n ∈ N∗. Int. J. Anal. Appl. 19 (2) (2021) 250 We shall verify the conditions (H1) − (H3). Evidently, f is continuous in J ×E and ‖f(t,y(t))‖≤ √ t (1 + t 3 2 )e10t ‖y(t)‖ + 2t (1 + t2)2 . With the aid of simple computation we find that∫ ∞ 0 e−5tdt = 1 10 < Γ( 3 2 ) and ∫ ∞ 0 2t (1 + t2)2 dt = 1 < ∞. Finally, we verify condition (H3). For any bounded set B ⊂ E, we have f(t,B(t)) = √ t (1 + t 3 2 )e5t B(t) + { 2t (1 + t2)2 }. Then γ(f(t,B(t)) ≤ √ t (1 + t 3 2 )e5t γ(B(t)). Since ∫∞ 0 e−10tdt = 0.1 < Γ( 3 2 ), we conclude that condition (H3) is satisfied. Therefore, Theorem 3.1 ensures that problem (4.1)-(4.3) has a solution. Acknowledgments: The authors would like to express their thanks to the editor and anonymous referees for his/her comments that improved the quality of the paper. Conflicts of Interest: The author(s) declare that there are no conflicts of interest regarding the publication of this paper. References [1] R. P. Agarwal, B. Hedia and M. Beddani, Structure of solution sets for implulsive fractional differential equations,Fract. Calc. Appl. Anal. 9 (2018), 15-36. [2] R. P. Agarwal, M. Meehan and D. O’Regan, Fixed Point Theory and Applications , Cambridge Tracts in Mathematics, 141 , Cambridge University Press, Cambridge, 2001. [3] B. Ahmad, Existence of solutions for irregular boundary value problems of nonlinear fractional differential equations, Appl. Math. Lett. 23 (2010), 390-394. [4] A. Arara, M. Benchohra, N. Hamidi and J.J. Nieto, Fractional order differential equations on an unbounded domain, Nonlinear Anal., Theory Methods Appl. 72 (2010), 580-586. [5] Z.B. Bai and H.S. Lü, Positive solutions for boundary value problem of nonlinear fractional differential equation, J. Math. Anal. Appl. 311 (2005), 495-505. [6] K. Balachandran and J.Y. Park, Nonlocal Cauchy problem for abstract fractional semilinear evolution equations, Nonlinear Anal., Theory Methods Appl. 71 (2009), 4471-4475. [7] K. Balachandran and J.J. Trujillo, The nonlocal Cauchy problem for nonlinear fractional integrodifferential equations in Banach spaces, Nonlinear Anal., Theory Methods Appl. 72 (2010), 4587-4593. [8] K. Balachandran, S. Kiruthika and J.J. Trujillo, Existence results for fractional impulsive integrodifferential equations in Banach spaces, Commun. Nonlinear Sci. Numer. Simul. 16 (2011), 1970-1977. [9] M. Benchohra, S. Hamani and S.K. Ntouyas, Boundary value problems for differential equations with fractional order and nonlocal conditions, Nonlinear Anal., Theory Methods Appl. 71 (2009), 2391-2396. Int. J. Anal. Appl. 19 (2) (2021) 251 [10] L. Byszewski, Existence and uniqueness of mild and classical solutions of semilinear functional-differential evolution nonlocal Cauchy problem, Selected problems of mathematics, 50th Anniv. Cracow Univ. Technol. Anniv. Issue 6, Cracow Univ. Technol. Krakow, (1995), 25-33. [11] L. Byszewski and V.Lakshmikantham, Theorem about the existence and uniqueness of a solution of a nonlocal abstract Cauchy problem in a Banach space, Appl. Anal. 40 (1991), 11-19. [12] G. Christopher, Existence and uniqueness of solutions to a fractional difference equation with nonlocal conditions, Com- puters Math. Appl. 61(2011), 191-202. [13] W. Cheung, J. Ren, P.J.Y. Wong and D. Zhao, Multiple positive solutions for discrete nonlocal boundary value problems, J. Math. Anal. Appl. 330 (2007), 900-915. [14] K. Deng, Exponential decay of solutions of semilinear parabolic equations with nonlocal initial conditions, J. Math. Anal. Appl. 179 (1993), 630-637. [15] A. M. A. El-Sayed, Nonlinear functional differential equations of arbitrary orders, Nonlinear Anal., Theory Methods Appl. 33 (1998), 181-186. [16] A. M. A. El-Sayed and A. G. Ibrahim, Multivalued fractional differential equations, Appl. Math. Comput. 68 (1995), 15-25. [17] D.J. Guo, V. Lakshmikantham and X. Liu, Nonlinear Integral Equations in Abstract Spaces, Kluwer Academic Publishers, Dordrecht, 1996. [18] A.A. Kilbas, H.M. Srivastava and J.J. Trujillo, Theory and Applications of Fractional Differential Equations, Elsevier B.V. Amsterdam, 2006. [19] G. M. N’Guérékata, A Cauchy problem for some fractional abstract differential equation with non local conditions, Non- linear Anal., Theory Methods Appl. 70 (2009), 1873-1876. [20] I. Podlubny, Fractional Differential Equations, in: Mathematics in Science and Engineering, vol. 198, Academic Press, New York, London, Toronto, 1999. [21] H.A.H. Salem, On the fractional calculus in abstract spaces and their applications to the Dirichlet-type problem of fractional order, Comput. Math. Appl. 59 (2010), 1278-1293. [22] H.A.H. Salem, Multi-term fractional differential equation in reflexive Banach space, Math. Comput. Model. 49 (2009), 829-834. [23] S.G. Samko, A.A. Kilbas and O.I. Marichev, Fractional Integrals and Derivatives: Theory and Applications, Gordon and Breach, Yverdon, 1993. [24] S. Szufla, On the application of measure of noncompactness to existence theorems, Rend. Sem. Mat. Univ. Padova. 75 (1986), 1-14. [25] X. Su, Solutions to boundary value problem of fractional order on unbounded domains in a Banach space, Nonlinear Anal., Theory Methods Appl. 74 (2011), 2844-2852. [26] S. Zhang, Positive solutions for boundary-value problems of nonlinear fractional differential equations, Electron. J. Differ. Equations, 2006 (2006), 36. 1. Introduction 2. Preliminary results 3. Main result 4. Example References