CONTACT: Faraj Y. Ishak faraj.ishak@uod.ac Department of Statistics, Collage of Administration & Economics University of Duhok, Iraq The article can be accessed here. https://doi.org/10.15642/mantik.2022.8.2.89-98 Jurnal Matematika MANTIK Vol. 8, No. 2, November 2022, pp.89-98 ISSN: 2527-3159 (print) 2527-3167 (online) Mixed Boundary Value Problem for Nonlinear Fractional Volterra Integral Equation Faraj Y. Ishak University of Duhok Iraq, faraj.ishak@uod.ac Article history: Received Sep 9, 2022 Revised, Dec 9, 2022 Accepted, Dec 31, 2022 Kata Kunci: Persamaan Volterra, teorema titik tetap Krasnoselskii, prinsip kontraksi Banach, teori Leray-Schauder degree. Abstrak. Artikel ini menyajikan hasil penelitian tentang eksistensi dari solusi persamaan integral fraksional nonlinier tipe Volterra dengan kondisi batas campuran, beberapa hipotesis yang diperlukan telah dikembangkan untuk membuktikan keberadaan solusi persamaan yang diusulkan. Teorema Krasnoselskii, prinsip Banach Contraction dan teori derajat Leray-Schauder adalah teorema dasar yang digunakan di sini untuk mencari solusi hasil. Dalam artikel ini juga diberikan contoh sederhana dari penerapan hasil persamaannya. Keywords: Volterra equation, Krasnoselskii theorem, Banach contraction principle, Leray- Schauder degree theory. Abstract. In this paper we present the existence of solutions for a nonlinear fractional integral equation of Volterra type with mixed boundary conditions, some necessary hypotheses have been developed to prove the existence of solutions to the proposed equation. Krasnoselskii Theorem, Banach Contraction principle and Leray-Schauder degree theory are the basic theorems used here to find the results. A simple example of application of the main result is presented. How to cite: F. Y. Ishak, β€œMixed Boundary Value Problem for Nonlinear Fractional Volterra Integral Equation”, J. Mat. Mantik, vol. 8, no. 2, pp. 89-98, December 2022. https://doi.org/10.15642/mantik.2021.7.1.9-19 http://u.lipi.go.id/1458103791 Jurnal Matematika MANTIK Vol. 8, No. 2, December 2022, pp. 89-98 90 1. Introduction Fractional calculus is the field of mathematical analysis which deals with the investigation and applications of integrals and derivatives of arbitrary order, the fractional calculus may be considered an old and yet novel topic. Recently, fractional differential equations have been of great interest. This is because of both the intensive development of the theory of fractional calculus itself and its applications in various sciences, such as physics, mechanics, chemistry, engineering.[1],[2],[3]. Integral equations appear in many engineering and scientific fields, such as unsteady aerodynamics, viscoelasticity, fluid dynamics, lots of population growth systems, neural network analysis, mathematical analysis of particle diffusion in an unstable fluid, heat conduction in memory resources, transmission lines, Population dynamics theory, nuclear reactors, inheritance systems. For details, see [4], [5], [6], [7], [8]. Boundary value problems have different applications. In addition to the previously mentioned fields, this type of problem appears in chemical engineering sciences, models of electromagnetic systems and thermoelectric theory. For more detailed information on boundary conditions, see [9], [10]. For more details on local and non-local boundary conditions, see [11],[12],[13],[14],[15],[16]. Feng, Zhang and Yang [13] in 2011 studied the existence and multiplicity solution to the nonlocal boundary value problem, fixed-point theorems in the cone were the main tool to prove the solutions. In 2014 Nyamoradi and Alaei [17] employed the Guo – Krasnoselskii fixed point theorem in a cone to study the existence of solution to a new fractional nonlocal mixed boundary value problem. In 2022 Ishak [18] investigated the existence solution for a fractional BVP of the first sort with Hadamard type and three-point boundary conditions using Krasnoselskii Zabriko theorem and Banach contraction principle. It is also well known that fixed-point theorems have been applied to various boundary value problems to show the existence of solutions; for example, see [3],[5]. However, this researcher’s remains not enough compared to the broad applications of this type of equations. The aim of this paper is to fill this gap. in this study we will investigate the existence and uniqueness solutions for the boundary value problem: 𝑫 𝒄 πœΆπ’™(𝒕) = π’ˆ(𝒕) + ∫ 𝝍(𝒕, 𝒔)𝝓(𝒕, 𝒔, 𝒙(𝒔))𝒅𝒔 𝒕 βˆ’βˆž π‘₯(0) = π‘Žπ‘₯(𝛾) + 𝑏, π‘₯ ́(0) = Ο‰ , 0 ≀ 𝑑 ≀ 1 , 1 < 𝛼 ≀ 2 (1) Where 𝑫 𝒄 indicates the Caputo fractional operator 𝝓: [𝟎, 𝟏]π˜…[𝟎, 𝟏]π˜…π— β†’ 𝐗 is a given continuous function in Banach space (𝐗 ,...) and 𝐂 = 𝐂([𝟎, 𝟏], 𝐗) is Banach space of all continuous functions from [0,1]β†’ 𝐗 endowed with the norm denoted by β€–. β€–, 𝒂 , 𝒃, π›š [𝟎, +∞), 𝝍: [𝟎, 𝟏]π˜…[𝟎, 𝟏] β†’ 𝐗 is a given kernel , π’ˆ: [𝟎, 𝟏] β†’ [𝟎, +∞) is known continuous function. 2. Preliminaries In this section we will mention some basic definitions in fractional calculus. Definition 2.1: [19] The fractional integral of order q is defined by πΌπ‘ž 𝑓(𝑑) = 1 Ξ“(π‘ž) ∫ (𝑑 βˆ’ 𝑠)π‘žβˆ’1 𝑑 0 𝑓(𝑠)𝑑𝑠, π‘ž > 0 provided the integral exists. Faraj Y. Ishak Mixed Boundary Value Problem for Nonlinear Fractional Volterra Integral Equation 91 Definition 2.2: [19] The fractional derivative of order q is defined by π·π‘ž 𝑓(𝑑) = 1 Ξ“(𝑛 βˆ’ π‘ž) ( 𝑑 𝑑𝑑 ) 𝑛 ∫ (𝑑 βˆ’ 𝑠)π‘›βˆ’π‘žβˆ’1 𝑑 0 𝑓(𝑠)𝑑𝑠, 𝑛 βˆ’ 1 < π‘ž ≀ 𝑛, π‘ž > 0, Provided the right-hand side is pointwise defined on (0, +∞). Lemma 2.1: [18] For Ξ±, Ξ² > 0, then the following relation hold: 𝐷𝛼 𝑑𝛽 = Ξ“(𝛽 + 1) Ξ“(𝛽 + 1 βˆ’ 𝛼) π‘‘π›½βˆ’π›Όβˆ’1, 𝛽 > 𝑛 π‘Žπ‘›π‘‘ 𝐷𝛼 π‘‘π‘˜ = 0, π‘˜ = 0,1, … , 𝑛 βˆ’ 1 Lemma 2.2: [18] Let 𝛼 > 0, then the differential equation 𝑐 𝐷0+ 𝛼 π‘₯(𝑑) = 0 Has a unique solution π‘₯(𝑑) = 𝑐0 + 𝑐1𝑑 + β‹― π‘π‘›βˆ’1𝑑 π‘›βˆ’1, 𝑐𝑖 ∈ 𝑅, 𝑖 = 1,2, … , 𝑛, where 𝑛 βˆ’ 1 < 𝛼 ≀ 𝑛 In view of Lemma 2.2, it follows that πΌπ‘ž 𝑐 π·π‘ž π‘₯(𝑑) = π‘₯(𝑑) + 𝑐0 + 𝑐1𝑑 + β‹― π‘π‘›βˆ’1𝑑 π‘›βˆ’1, 𝑐𝑖 ∈ 𝑅, 𝑖 = 1,2, … , 𝑛 Theorem 2.1: [5] (Krasnoselskii fixed point theorem) Let M be a closed convex and nonempty subset of a Banach space X. Let A, B be the operators such that (i) Ax + By ∈ M whenever x, y ∈ M (ii) A is compact and continuous (iii) B is a contraction mapping. Then there exists z ∈ M such that z = Az + Bz. Theorem 2.2: (Arzela -Ascoli theorem) Let 𝛺 be a compact Hausdorff metric space. Then 𝑀 βŠ‚ 𝐢(𝛺) is relatively compact ⟺ 𝑀 is uniformly bounded and uniformly equicontinuous. Lemma 2.3: Given 𝑓 ∈ 𝐢(0,1) ∩ 𝐿(0,1), the unique solution of (1) is: π‘₯(𝑑) = ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝑑 0 𝑓(𝑠)𝑑𝑠 + π‘Ž 1 βˆ’ π‘Ž ∫ (𝛾 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝑓(𝑠)𝑑𝑠 𝛾 0 + π‘Žπœ”π›Ύ + 𝑏 1 βˆ’ π‘Ž + πœ”π‘‘ (2) Where, 𝑓(𝑑) = 𝑔(𝑑) + ∫ πœ“(𝑑, 𝑠)πœ™(𝑑, 𝑠, π‘₯(𝑠))𝑑𝑠 𝑑 βˆ’βˆž Proof: In view of lemma (2.2) the fractional differential equation (1) is equivalent to the integral equation: π‘₯(𝑑) = 𝐼0+ 𝛼 𝑓(𝑑) + 𝑐0 + 𝑐1𝑑 π‘₯(𝑑) = ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝑑 0 𝑓(𝑠)𝑑𝑠 + 𝑐0 + 𝑐1𝑑 Where 𝑐0, 𝑐1 ∈ 𝑅. From the boundary conditions (1), we have 𝑐1 = πœ” and 𝑐0 = π‘Ž 1 βˆ’ π‘Ž ∫ (𝛾 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝑓(𝑠)𝑑𝑠 𝛾 0 + π‘Žπœ”π›Ύ + 𝑏 1 βˆ’ π‘Ž Jurnal Matematika MANTIK Vol. 8, No. 2, December 2022, pp. 89-98 92 By substituting 𝑐0, 𝑐1 in π‘₯(𝑑), the proof will be completed . We will need the following hypotheses: (H1) for 𝐾 ∈ 𝑅+ the inequality holds: β€–πœ™(𝑑, 𝑠, π‘₯2) βˆ’ πœ™(𝑑, 𝑠, π‘₯1)β€– ≀ 𝐾‖π‘₯2 βˆ’ π‘₯1β€–, for all 𝑑, 𝑠 ∈ [0,1], π‘₯1, π‘₯2 ∈ 𝑋 (H2) β€–πœ™(𝑑, 𝑠, π‘₯)β€– ≀ 𝐿 for all 𝑑, 𝑠, π‘₯ ∈ [0,1]𝗑[0,1]𝗑X, L ∈ 𝑅+ Further ‖𝑔(𝑑)β€– ≀ πœ‰ , β€–πœ“(𝑑, 𝑠)β€– ≀ 𝛿𝑒 βˆ’πœ†(π‘‘βˆ’π‘ ) for all πœ‰, 𝛿, πœ† ∈ 𝑅+ 3. Main Result Proves of theorems of existence and uniqueness solution for equation (1) will be given in this section. Theorem 3.1: Suppose that πœ™: [0,1]𝗑[0,1]𝗑 X β†’ X is continuous and fulfilled H1and H2, if: π‘Žπ›Ώ 𝐾𝛾𝛼 πœ†(1 βˆ’ π‘Ž)Ξ“(𝛼 + 1) < 1 (3) Then equation (1) has at least one solution. Proof: Let πœ‘π‘Ÿ = {π‘₯ ∈ 𝐢: β€–π‘₯β€– ≀ π‘Ÿ} where: π‘Žπ›Ύπ›Ό (πœ†πœ‰ + 𝛿𝐿) πœ†(1 βˆ’ π‘Ž)Ξ“(𝛼 + 1) + πœ†πœ‰ + 𝛿𝐿 πœ†Ξ“(𝛼 + 1) + π‘Žπœ”π›Ύ + 𝑏 1 βˆ’ π‘Ž + πœ” ≀ π‘Ÿ define tow mapping F, G on πœ‘π‘Ÿ s.t. (𝐹π‘₯)(𝑑) = ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝑑 0 𝑓(𝑠)𝑑𝑠 (𝐺π‘₯)(𝑑) = π‘Ž 1 βˆ’ π‘Ž ∫ (𝛾 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝑓(𝑠)𝑑𝑠 𝛾 0 + π‘Žπœ”π›Ύ + 𝑏 1 βˆ’ π‘Ž + πœ”π‘‘ For π‘₯, 𝑦 ∈ πœ‘π‘Ÿ, by (H2) we obtain: β€–(𝐹π‘₯)(𝑑) + (𝐺π‘₯)(𝑑)β€– ≀ ∫ (π‘‘βˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) ‖𝑔(𝑠)‖𝑑𝑠 + 𝑑 0 ∫ (π‘‘βˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) (∫ β€–πœ“(𝑑, 𝑠)β€– 𝑑 βˆ’βˆž 𝑑 0 β€–πœ™(𝑑, 𝑠, π‘₯(𝑠))‖𝑑𝑠)𝑑𝑠 + | π‘Ž 1βˆ’π‘Ž | ∫ (π›Ύβˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) ‖𝑔(𝑠)‖𝑑𝑠 + π‘Ž 1βˆ’π‘Ž 𝛾 0 ∫ (π›Ύβˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) ( 𝛾 0 ∫ β€–πœ“(𝑑, 𝑠)β€– 𝑑 βˆ’βˆž β€–πœ™(𝑑, 𝑠, π‘₯(𝑠))‖𝑑𝑠)𝑑𝑠 + | π‘Žπœ”π›Ύ+𝑏 1βˆ’π‘Ž | + |πœ”π‘‘| ≀ πœ‰ Ξ“(𝛼+1) + 𝛿 πœ† ∫ (π‘‘βˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) 𝐿𝑑𝑠 𝑑 0 + π‘Žπœ‰π›Ύπ›Ό (1βˆ’π‘Ž)Ξ“(𝛼+1) + π‘Žπ›Ώ πœ†(1βˆ’π‘Ž) ∫ (π›Ύβˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) 𝐿𝑑𝑠 𝛾 0 + π‘Žπœ”π›Ύ+𝑏 1βˆ’π‘Ž + πœ”π‘‘ ≀ πœ‰ Ξ“(𝛼+1) + 𝛿𝐿 πœ†Ξ“(𝛼+1) + π‘Žπœ‰π›Ύπ›Ό (1βˆ’π‘Ž)Ξ“(𝛼+1) + π‘Žπ›ΏπΏπ›Ύπ›Ό πœ†(1βˆ’π‘Ž)Ξ“(𝛼+1) + π‘Žπœ”π›Ύ+𝑏 1βˆ’π‘Ž + πœ” ≀ π‘Žπ›Ύπ›Ό(πœ†πœ‰+𝛿𝐿) πœ†(1βˆ’π‘Ž)Ξ“(𝛼+1) + πœ†πœ‰+𝛿𝐿 πœ†Ξ“(𝛼+1) + π‘Žπœ”π›Ύ+𝑏 1βˆ’π‘Ž + πœ” ≀ π‘Ÿ Which means 𝐹π‘₯ + 𝐺π‘₯ ∈ πœ‘π‘Ÿ . Faraj Y. Ishak Mixed Boundary Value Problem for Nonlinear Fractional Volterra Integral Equation 93 Since F is continuous because Ο• is continuous, we have to prove that 𝐹 is compact. (𝐹π‘₯)(t) is uniformly bounded on πœ‘π‘Ÿ , as: β€–(𝐹π‘₯)(𝑑)β€– ≀ πœ†πœ‰ + 𝛿𝐿 πœ†Ξ“(𝛼 + 1) Since πœ™ is bounded on [0,1]𝗑[0,1]π—‘πœ‘π‘Ÿ let: πœ™π‘šπ‘Žπ‘₯ = π‘ π‘’π‘βŸ 𝑠,𝑑,π‘₯(𝑑)∈[0,1]𝗑[0,1]π—‘πœ‘π‘Ÿ β€–πœ™(𝑑, 𝑠, π‘₯(𝑑))β€– Then for 𝑑1, 𝑑2 ∈ [0,1] we get β€–(𝐹π‘₯)(𝑑2) βˆ’ (𝐹π‘₯)(𝑑1)β€– ≀ 1 Ξ“(𝛼) ∫ β€–((𝑑2 βˆ’ 𝑠) π›Όβˆ’1 βˆ’ (𝑑1 βˆ’ 𝑠) π›Όβˆ’1)𝑓(𝑠)𝑑𝑠‖ 𝑑1 0 + 1 Ξ“(𝛼) ∫ β€–(𝑑2 βˆ’ 𝑠) π›Όβˆ’1𝑓(𝑠)𝑑𝑠‖ 𝑑2 𝑑1 ≀ 1 Ξ“(𝛼) ∫ β€–((𝑑2 βˆ’ 𝑠) π›Όβˆ’1 βˆ’ (𝑑1 βˆ’ 𝑠) π›Όβˆ’1) (𝑔(𝑠) + 𝑑1 0 ∫ πœ“(𝑑, 𝑠)πœ™(𝑑, 𝑠, π‘₯(𝑠)) 𝑑 βˆ’βˆž 𝑑𝑠)β€– 𝑑𝑠 + 1 Ξ“(𝛼) ∫ β€–(𝑑2 βˆ’ 𝑠) π›Όβˆ’1 (𝑔(𝑠) + 𝑑2 𝑑1 ∫ πœ“(𝑑, 𝑠)πœ™(𝑑, 𝑠, π‘₯(𝑠)) 𝑑 βˆ’βˆž 𝑑𝑠)β€– 𝑑𝑠 ≀ πœ‰|(𝑑2 βˆ’ 𝑑1) 𝛼 βˆ’ 𝑑2 𝛼 | Ξ“(𝛼 + 1) + π›Ώπœ™π‘šπ‘Žπ‘₯ |(𝑑2 βˆ’ 𝑑1) 𝛼 βˆ’ 𝑑2 𝛼 | πœ†Ξ“(𝛼 + 1) + πœ‰π‘‘1 𝛼 Ξ“(𝛼 + 1) + π›Ώπœ™π‘šπ‘Žπ‘₯ 𝑑1 𝛼 πœ†Ξ“(𝛼 + 1) βˆ’ πœ‰|(𝑑2 βˆ’ 𝑑1) 𝛼 | Ξ“(𝛼 + 1) βˆ’ π›Ώπœ™π‘šπ‘Žπ‘₯ |(𝑑2 βˆ’ 𝑑1) 𝛼 | πœ†Ξ“(𝛼 + 1) ≀ ( πœ‰ Ξ“(𝛼 + 1) + π›Ώπœ™π‘šπ‘Žπ‘₯ πœ†Ξ“(𝛼 + 1) )|𝑑1 𝛼 βˆ’ 𝑑2 𝛼 | Which is independent of π‘₯ there for (𝐹π‘₯)(𝑑 ) is relatively compact on πœ‘π‘Ÿ ,by Arzela- Ascoli’s theorem (𝐹π‘₯)(𝑑 ) is compact in πœ‘π‘Ÿ . For π‘₯, 𝑦 ∈ πœ‘π‘Ÿ and 𝑑 ∈ [0,1], by H1 we have: β€–(𝐺π‘₯)(𝑑) βˆ’ (𝐺𝑦)(𝑑)β€– ≀ π‘Ž 1βˆ’π‘Ž ∫ (π›Ύβˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) ( 𝛾 0 ∫ β€–πœ“(𝑑, 𝑠)β€– 𝑑 βˆ’βˆž β€–πœ™(𝑑, 𝑠, π‘₯(𝑠))‖𝑑𝑠)𝑑𝑠 βˆ’ π‘Ž 1βˆ’π‘Ž ∫ (π›Ύβˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) ( 𝛾 0 ∫ β€–πœ“(𝑑, 𝑠)β€– 𝑑 βˆ’βˆž β€–πœ™(𝑑, 𝑠, 𝑦(𝑠))‖𝑑𝑠)𝑑𝑠 ≀ π‘Ž 1 βˆ’ π‘Ž ∫ (𝛾 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) ( 𝛾 0 ∫ 𝛿𝑒 βˆ’πœ†(π‘‘βˆ’π‘ )β€–πœ™(𝑑, 𝑠, π‘₯(𝑠)) βˆ’ πœ™(𝑑, 𝑠, 𝑦(𝑠))β€– 𝑑 βˆ’βˆž 𝑑𝑠)𝑑𝑠 ≀ π‘Žπ›Ώ πœ†(1βˆ’π‘Ž) ∫ (π›Ύβˆ’π‘ )π›Όβˆ’1𝐾 Ξ“(𝛼) β€–π‘₯ βˆ’ 𝑦‖𝑑𝑠 𝛾 0 ≀ π‘Žπ›Ώ 𝐾𝛾𝛼 πœ†(1βˆ’π‘Ž)Ξ“(𝛼+1) β€–π‘₯ βˆ’ 𝑦‖ (4) Jurnal Matematika MANTIK Vol. 8, No. 2, December 2022, pp. 89-98 94 It follows from (4) that (𝐺π‘₯)(𝑑) is contraction mapping, this completes the prove. Theorem 3.2: Suppose that πœ™: [0,1]𝗑[0,1]𝗑X β†’ X is continuous and fulfilled (H1). If: Ξ© = 𝛿𝐾 + π‘Žπ›ΏπΎ(𝛾𝛼 βˆ’ 1) πœ†(1 βˆ’ π‘Ž)𝛀(𝛼 + 1) < 1 (5) Then equation (1) has a unique solution. Proof: Let Ξ¦: 𝐢 β†’ 𝐢 is defined as: (Ξ¦π‘₯)(𝑑) = ∫ (π‘‘βˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) 𝑑 0 𝑓(𝑠)𝑑𝑠 + π‘Ž 1βˆ’π‘Ž ∫ (π›Ύβˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) 𝑓(𝑠)𝑑𝑠 𝛾 0 + π‘Žπœ”π›Ύ+𝑏 1βˆ’π‘Ž + πœ”π‘‘, 𝑑 ∈ [0,1] let π‘ π‘’π‘π‘‘βˆˆ[0,1]|πœ™(𝑑, 𝑠, 0)| = 𝑀 and choose: π‘Ÿ β‰₯ πœ†πœ‰+𝛿𝑀 (1βˆ’π›Ί)λΓ(𝛼+1) + π‘Žπ›Ύπ›Ό(πœ†πœ‰+𝛿𝑀) (1βˆ’π›Ί)Ξ»π‘ŽΞ“(𝛼+1) + π‘Žπœ”π›Ύ+𝑏 (1βˆ’π›Ί)(1βˆ’π‘Ž) + πœ”π‘‘ (1βˆ’π›Ί) (6) It is claimed that Ξ¦πœ‘π‘Ÿ βŠ‚ πœ‘π‘Ÿ where: πœ‘π‘Ÿ = {π‘₯ ∈ 𝐢: β€–π‘₯β€– ≀ π‘Ÿ} In fact, for π‘₯ ∈ πœ‘π‘Ÿ , by (4), (5) and H1 we obtain: β€–(Ξ¦π‘₯)(𝑑)β€– ≀ ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝑑 0 ‖𝑔(𝑠)‖𝑑𝑠 + ∫ (π‘‘βˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) 𝑑 0 (∫ β€–πœ“(𝑑, 𝑠)β€– 𝑑 βˆ’βˆž β€–πœ™(𝑑, 𝑠, π‘₯(𝑠))‖𝑑𝑠) 𝑑𝑠 + π‘Ž 1βˆ’π‘Ž ∫ (π›Ύβˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) ‖𝑔(𝑠)‖𝑑𝑠 𝛾 0 + π‘Ž 1βˆ’π‘Ž ∫ (π›Ύβˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) (∫ β€–πœ“(𝑑, 𝑠)β€– 𝑑 βˆ’βˆž β€–πœ™(𝑑, 𝑠, π‘₯(𝑠))‖𝑑𝑠) 𝑑𝑠 𝛾 0 + | π‘Žπœ”π›Ύ+𝑏 1βˆ’π‘Ž | + |πœ”π‘‘| ≀ πœ‰ 𝛀(𝛼+1) + ∫ (π‘‘βˆ’π‘ )π›Όβˆ’1 𝛀(𝛼) ∫ 𝛿𝑒 βˆ’πœ† (π‘‘βˆ’π‘ ) 𝑑 βˆ’βˆž (β€–πœ™(𝑑, 𝑠, π‘₯(𝑠)) βˆ’ πœ™(𝑑, 𝑠, 0)β€– + 𝑑 0 β€–πœ™(𝑑, 𝑠, 0)β€–)𝑑𝑠 𝑑𝑠 + π‘Žπœ‰π›Ύπ›Ό (1βˆ’π‘Ž)𝛀(𝛼+1) + π‘Ž 1βˆ’π‘Ž ∫ (π›Ύβˆ’π‘ )π›Όβˆ’1 𝛀(𝛼) (∫ 𝛿𝑒 βˆ’πœ† (π‘‘βˆ’π‘ ) 𝑑 βˆ’βˆž β€–πœ™(𝑑, 𝑠, π‘₯(𝑠)) βˆ’ 𝛾 0 πœ™(𝑑, 𝑠, 0)β€– + β€–πœ™(𝑑, 𝑠, 0)‖𝑑𝑠)𝑑𝑠 + π‘Žπœ”π›Ύ+𝑏 1βˆ’π‘Ž + πœ”π‘‘ ≀ πœ‰ Ξ“(𝛼+1) + π‘Ÿπ›ΏπΎ λΓ(𝛼+1) + 𝛿𝑀 λΓ(𝛼+1) + π‘Žπœ‰π›Ύπ›Ό (1βˆ’π‘Ž)Ξ“(𝛼+1) + π‘Ÿπ‘Žπ›ΏπΎπ›Ύπ›Ό πœ†(1βˆ’π‘Ž)𝛀(𝛼+1) + π‘Žπ›Ώπ‘€π›Ύπ›Ό πœ†(1βˆ’π‘Ž)𝛀(𝛼+1) + π‘Žπœ”π›Ύ+𝑏 1βˆ’π‘Ž + πœ”π‘‘ ≀ π‘Ÿ ( 𝛿𝐾 + π‘Žπ›ΏπΎ(𝛾𝛼 βˆ’ 1) πœ†(1 βˆ’ π‘Ž)𝛀(𝛼 + 1) ) + πœ†πœ‰ + 𝛿𝑀 λΓ(𝛼 + 1) + π‘Žπ›Ύπ›Ό (πœ†πœ‰ + 𝛿𝑀) πœ†(1 βˆ’ π‘Ž)𝛀(𝛼 + 1) + π‘Žπœ”π›Ύ + 𝑏 1 βˆ’ π‘Ž + πœ”π‘‘ ≀ π‘Ÿπ›Ί + (1 βˆ’ 𝛺)π‘Ÿ = π‘Ÿ Now we have to prove that the function Ξ¦ is contraction. For π‘₯, 𝑦 ∈ 𝐢 and 𝑑 ∈ [0,1], by (5) and H1 we have: β€–(Ξ¦π‘₯)(𝑑) βˆ’ (Φ𝑦)(𝑑)β€– Faraj Y. Ishak Mixed Boundary Value Problem for Nonlinear Fractional Volterra Integral Equation 95 ≀ ∫ (π‘‘βˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) (∫ β€–πœ“(𝑑, 𝑠)β€– 𝑑 βˆ’βˆž β€–πœ™(𝑑, 𝑠, π‘₯(𝑠)) βˆ’ πœ™(𝑑, 𝑠, 𝑦(𝑠))‖𝑑𝑠) 𝑑 0 𝑑𝑠 + π‘Ž 1βˆ’π‘Ž ∫ (π›Ύβˆ’π‘ )π›Όβˆ’1 Ξ“(𝛼) (∫ β€–πœ“(𝑑, 𝑠)β€– 𝑑 βˆ’βˆž β€–πœ™(𝑑, 𝑠, π‘₯(𝑠)) βˆ’ πœ™(𝑑, 𝑠, 𝑦(𝑠))‖𝑑𝑠)𝑑𝑠 𝛾 0 ≀ ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝐾‖π‘₯ βˆ’ 𝑦‖(∫ 𝛿𝑒 βˆ’πœ†(π‘‘βˆ’π‘ ) 𝑑 βˆ’βˆž 𝑑𝑠 𝑑 0 + π‘Ž 1 βˆ’ π‘Ž ∫ (𝛾 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝐾‖π‘₯ βˆ’ 𝑦‖(∫ 𝛿𝑒 βˆ’πœ†(π‘‘βˆ’π‘ ) 𝑑 βˆ’βˆž 𝑑𝑠)𝑑𝑠 𝛾 0 ≀ 𝛿𝐾‖π‘₯ βˆ’ 𝑦‖ λΓ(𝛼 + 1) + π‘Žπ›Ώπ›Ύπ›Ό 𝐾‖π‘₯ βˆ’ 𝑦‖ πœ†(1 βˆ’ π‘Ž)Ξ“(𝛼 + 1) ≀ 𝛿𝐾 + π‘Žπ›ΏπΎ(𝛾𝛼 βˆ’ 1) πœ†(1 βˆ’ π‘Ž)𝛀(𝛼 + 1) β€–π‘₯ βˆ’ 𝑦‖ ≀ Ξ©β€–π‘₯ βˆ’ 𝑦‖ Ξ© < 1 ensure that (Ξ¦π‘₯)(𝑑) is contractive. Therefor the conclusion of the theorem follows from the contraction mapping principle. Theorem 3.3: Let πœ™: [0, 𝑇] Γ— [0, 𝑇] Γ— 𝑅 β†’ 𝑅 , and let π‘˜ ∈ 𝑅 such that 0 ≀ π‘˜ < 1 Ξ© , where Ξ© = 𝑑𝛼 Ξ“(𝛼 + 1) + π‘Žπ›Ύπ›Ό (1 βˆ’ π‘Ž)Ξ“(𝛼 + 1) and M > 0 such that |πœ™(𝑑, 𝑠, π‘₯(𝑑))| ≀ π‘˜|π‘₯| + 𝑀 for all 𝑑 ∈ [0, 𝑇], π‘₯ ∈ 𝑅 then problem (1) has at least one solution. Proof: Define an operator Ξ¨: Ξ› β†’ Ξ› as: Ξ¨(𝑑) = ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝑑 0 𝑓(𝑠)𝑑𝑠 + π‘Ž 1 βˆ’ π‘Ž ∫ (𝛾 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝑓(𝑠)𝑑𝑠 𝛾 0 + π‘Žπœ”π›Ύ + 𝑏 1 βˆ’ π‘Ž + πœ”π‘‘ Where Ξ› = 𝐢([0,1], 𝑅) denote to the Bansch space of all continuous functions from [0,1] β†’ 𝑅 endowed with the norm defined by β€–π‘₯β€– = sup{|π‘₯(𝑑)|, 𝑑 ∈ [0,1]}. Let us define a fixed-point problem by: π‘₯ = Ξ¨π‘₯ (7) Now we need to prove the existence of at least one solution π‘₯ ∈ {0, 𝑇] satisfying (7). Define a ball β„¬π‘Ÿ βŠ‚ 𝐢[0, 𝑇] with π‘Ÿ > 0 as: β„¬π‘Ÿ = {π‘₯ ∈ 𝐢[0, 𝑇]: max π‘‘βˆˆ[0,𝑇] |π‘₯(𝑑)| < π‘Ÿ} Where π‘Ÿ well be given later, then it’s enough to show that β„¬π‘ŸΜ…Μ…Μ…Μ… β†’ 𝐢[0, 𝑇]satisfies: π‘₯ β‰  𝜎Ψπ‘₯, βˆ€π‘₯ ∈ πœ•β„¬π‘Ÿ π‘Žπ‘›π‘‘ βˆ€πœŽ ∈ [0, 𝑇] (8) Let us define 𝐻(𝜎, π‘₯) = 𝜎Ψπ‘₯, π‘₯ ∈ 𝐢(ℝ), 𝜎 ∈ [0, 𝑇] Then by Arzesla’-Ascoli theorem β„ŽπœŽ (π‘₯) = π‘₯ βˆ’ 𝐻(𝜎, π‘₯) = π‘₯ βˆ’ 𝜎Ψπ‘₯ is completely continuous if (8) is true then the following Jurnal Matematika MANTIK Vol. 8, No. 2, December 2022, pp. 89-98 96 Leray-Schauder degree are well define and by the homotopy invariance of topological degree it follows that: deg(β„ŽπœŽ , β„¬π‘Ÿ , 0) = deg(𝐼 βˆ’ 𝜎Ψπ‘₯, β„¬π‘Ÿ , 0) = deg(β„Ž1, β„¬π‘Ÿ , 0) = deg(β„Ž0, β„¬π‘Ÿ , 0) = deg(𝐼, β„¬π‘Ÿ , 0) = 1 β‰  0,0 ∈ β„¬π‘Ÿ. Where I denote the unit operator, by non-zero property of the Leray-Schauder degree β„Ž1(π‘₯) = π‘₯ βˆ’ 𝜎Ψπ‘₯ = 0 for at least one π‘₯ ∈ β„¬π‘Ÿ in order to prove (8) we assume that π‘₯ = 𝜎Ψπ‘₯ for some 𝜎 ∈ [0, 𝑇]and for all 𝑑 ∈ [0, 𝑇] such that: |π‘₯(𝑑)| = |𝜎Ψπ‘₯ | = ∫ (𝑑 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) 𝑑 0 (|𝑔(𝑑)| + ∫ |πœ“(𝑑, 𝑠)||πœ™(𝑑, 𝑠, π‘₯(𝑠))|𝑑𝑠 𝑑 βˆ’βˆž )𝑑𝑠 + π‘Ž 1 βˆ’ π‘Ž ∫ (𝛾 βˆ’ 𝑠)π›Όβˆ’1 Ξ“(𝛼) (|𝑔(𝑑)| + ∫ |πœ“(𝑑, 𝑠)||πœ™(𝑑, 𝑠, π‘₯(𝑠))|𝑑𝑠 𝑑 βˆ’βˆž )𝑑𝑠 𝛾 0 + | π‘Žπœ”π›Ύ + 𝑏 1 βˆ’ π‘Ž | + |πœ”π‘‘ | ≀ (πœ‰ + 𝛿(π‘˜|π‘₯| + 𝑀 πœ† )( 𝑑𝛼 Ξ“(𝛼 + 1) + π‘Žπ›Ύπ›Ό (1 βˆ’ π‘Ž)Ξ“(𝛼 + 1) ) + 𝑀1 ≀ (πœ‰ + 𝛿(π‘˜|π‘₯| + 𝑀 πœ† )Ξ© + 𝑀1 Which on taking norm (π‘ π‘’π‘π‘‘βˆˆ[0,𝑇]|π‘₯| = β€–π‘₯β€–) and solving for β€–π‘₯β€– yields: β€–π‘₯β€– = ΞΎΞ©(MΟƒ + 1) + 𝑀1 𝜎(𝜎 βˆ’ Ξ©π›Ώπ‘˜) Where 𝑀1 = | π‘Žπœ”π›Ύ+𝑏 1βˆ’π‘Ž | + |πœ”π‘‘ | , letting π‘Ÿ = ΞΎΞ©(MΟƒ + 1) + 𝑀1 𝜎(𝜎 βˆ’ Ξ©π›Ώπ‘˜) + 1 (8) hold, this completes the proof. Example: Consider the following fractional integrodifferential equation 𝐷3 2⁄ π‘₯(𝑑) = sin(𝑑) + ∫ (2𝑑 + 𝑠)(𝑑 + π‘₯(𝑠))𝑑𝑠 𝑑 βˆ’βˆž π‘₯(0) = 0.5π‘₯(1.25) + 3, �́�(0) = 1.5 (9) Comparing (9) and (1), we see that 𝛼 = 3 2⁄ , 𝑔(𝑑) = sin(𝑑) , πœ“(𝑑, 𝑠) = 2𝑑 + 𝑠, πœ™(𝑑, 𝑠, π‘₯(𝑑)) = 𝑑 + π‘₯(𝑠), 𝛾 = 1.25, π‘Ž = 0.5, 𝑏 = 3, πœ” = 1.5. If we choose πœ‰ = 1, 𝛿 = 1, πœ† = 5 , 𝐾 = 2, then H1 holds, and 𝛿𝐾 + π‘Žπ›ΏπΎ(𝛾𝛼 βˆ’ 1) πœ†(1 βˆ’ π‘Ž)𝛀(𝛼 + 1) = (1)(2) + (0.5)(1)(2)(1.253 2⁄ βˆ’ 1) (5)(1 βˆ’ 0.5)( 1.3293) < 1 That is, (5) holds. Thus, by theorem 3.2, equation (9) has a unique solution. Faraj Y. Ishak Mixed Boundary Value Problem for Nonlinear Fractional Volterra Integral Equation 97 4. Conclusion Based on the results and discussion, it can be concluded that the idea of Krasnoselskii fixed point theorem was very effective to proof the existence solution for the proposed equation. 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