Abstract
In this paper, we investigate new types of nonlocal implicit problems involving piecewise Caputo fractional operators. The existence and uniqueness results are proved by using some fixed point theorems. Furthermore, we present analogous results involving piecewise Caputo-Fabrizio and Atangana–Baleanu fractional operators. The ensuring of the existence of solutions is shown by Ulam-Hyer’s stability. At last, two examples are given to show and approve our outcomes.
1. Introduction
It merits noticing that fractional calculus (FC) has gotten significant thought from scientists and researchers. It is a result of its wide scope of uses in different fields and disciplines. The crucial concepts and definitions of FC have been presented in [1, 2]. In [3, 4], the authors introduced some fundamental history of fractional calculus and its applications to engineering and different areas of science.
Many classes of fractional differential equations (FDEs) have been intensively investigated in the last decades, for instance, theories involving the existence of unique solutions have been notarized [5–7]. Numerical and analytical methods have been evolving with the target to solve such equations [8–10]. These equations have been tracked as useful in modeling some real-world problems with incredible achievement.
The qualitative properties of solutions represent a very important aspect of the theory of FDEs. The formerly aforesaid region has been studied well for classical differential equations. However, for FDEs, there are many aspects that require further studying and reconnoitering. The attention on the existence and uniqueness has been especially focused by applying Riemann-Liouville (R-L), Caputo, Hilfer, and other FDs, see [11–15].
In this regard, Agarwal et al. [16] investigated the existence of solutions of the following Caputo type FDE:
The basic theory of implicit FDEs with Caputo FD has been investigated by Kucche et al. [17]. Wahash et al. [18] considered the following nonlocal implicit FDEs with -Caputo FD
Problem (2) with has been studied by Benchohra and Bouriah [19].
Motivated by the above works and inspired by [20], we consider the piecewise Caputo implicit FDE (PC-IFDE) of the type: and the following piecewise Caputo nonlocal implicit FDE (PC-NIFDE): where , , and represent the piecewise Caputo FD of order defined by where is a classical derivative on and is standard Caputo FD on .
It is essential to note that the utilization of nonlinear condition in physical issues yields better impact than the initial condition (see [21]).
We pay attention to the topic of the novel piecewise operators. As far as we could possibly know, no outcomes in the literature are addressing the qualitative aspects of the aforesaid problems by using the piecewise FC. Consequently, by conquering this gap, we will examine the existence, uniqueness, and Ulam-Hyers stability results of piecewise Caputo problems (3) and (4) based on the standard fixed point theorems due to Banach-type and Schauder-type. Furthermore, we present similar results containing piecewise Caputo-Fabrizio (PCF) type and piecewise Atangana-Baleanu (PAB) type. An open problem with respect to another function is suggested.
Remark 1. (i)If then problem (4) reduces to the PC-IFDE (3).(ii)If , then problem (4) has been studied by Benchohra and Bouriah [19], Haoues et al. [22], and Abdo et al. [11] for .(iii)Our current results for problem (4) stay available on PC-IFDE (3).The substance of this paper is coordinated as follows: Section 2 presents a few required outcomes and fundamentals about piecewise FC. Our key outcomes for problem (4) are proved in Section 3. Two examples to make sense of the gained outcomes are built in Section 4. Toward the end, we encapsulate our study in the end section.
2. Primitive Results
In this section, we present some concepts of a piecewise FC. Let
Obviously is a Banach space under .
Definition 2 [20]. Let and be a continuous. Then, the piecewise version of RL integral is given by where and
Definition 3 [20]. Let and be a continuous. Then, the piecewise version of Caputo derivative is given by where and
Lemma 4 [20]. Let and Then, the following PC-FDE has the following solution
Lemma 5 [20]. Let and for a given function, . Then, For our aim, we need the Banach fixed-point theorem [23] and the Schauder fixed-point theorem [24].
3. Main Results
In this section, we give some qualitative analyses of the PC-IFDE and PC-NIFDE.
Lemma 6. Let be continuous.
Then, PC-NIFDE (4) is equivalent to
where satisfies the functional equation
Proof. Let .
Then, by applying , we obtain
In view of Lemma 5, we have
Case 1. For
Case 2. For
Using the nonlocal condition in both cases we obtain
So, we get (12). On the other hand, let (13) be satisfied. Set
This implies that
Since on and on we obtain and hence
The next assumptions will be applied in the sequel:
() The functions and are continuous with that is a nondecreasing such that
() is continuous and compact with for
() There exist , such that and
() There exists , such that and for
Now, we shall prove the existence theorem for (4) based on Schauder’s theorem.
Theorem 7. Let () and () hold.
Then, piecewise Caputo FNIDE (4) has at least one solution on
Proof. Consider the operator , such that i.e., where with Define the ball where and , with
For any , and by (Assu), we have
Since , we obtain
Hence, the proceed is in the following steps:
Step 1. is bounded.
Case 1. For we have
Case 2. For we have
From (28) and (29), we conclude that Thus, Since is bounded, then is bounded.
Step 2. is continuous. Let a sequence such that in as Then, for we have For we have where with and Since as and , and are continuous, the Lebesgue dominated convergence theorem gives that
Step 3. is equicontinuous. Let then , we have Let then , we have Since is continuous and compact, (33) and (34) give That means is relatively compact on . So, is completely continuous due to the Arzela–Ascolli theorem. Thus, Schauder’s theorem shows that problem (4) has at least one solution.
Next, we prove the uniqueness theorem for (4) based on Banach’s theorem.
Theorem 8. Let ()-() hold.
If then PC-NIFDE (4) has a unique solution on , where
Proof. Consider and in , then which implies that
Hence, we have two cases:
Case 1. For
Case 2. For
Consequently,
Since , is a contraction. Thus, Banach’s theorem shows that PC-NIFDE (4) has a unique solution that exists on .
3.1. An Analogous Results
In this part, we show some analogous results according to our preceding outcomes.
3.1.1. Piecewise Caputo-Fabrizio NIFDE (PCF-NIFDE)
Consider the following PCF-NIFDE where is the piecewise derivative in the Caputo-Fabrizio sense (see [20]) defined by where and are the classical Caputo-Fabrizio FD (see [25]).
Let based on PCF-NIFDE (42), the results in Theorems 7 and 8 can be presented by where and are a Caputo-Fabrizio integral on (see [25])
3.1.2. Piecewise Atangana-Baleanu NIFDE (PAB-NIFDE)
Consider the following PAB-NIFDE where is the piecewise derivative in the Atangana-Baleanu sense defined by (see [20]) where is the normalization function that satisfies ; and are the classical Atangana-Baleanu FD ([26]).
Based on PAB-NIFDE (45), the results in Theorems 7 and 8 can be presented by where is the Atangana-Baleanu integral on (see [26])
Remark 9. Following the strategy of proof utilized in the previous part, we can get the existence results for nonlinear problems (42) and (45).
3.2. UH Stability Analysis
In this portion, we give the UH Stability of problem (4).
Definition 10. PC-NIFDE (4) is UH stable if there exists a such that for all and each solution of the inequality. there exists a solution of PC-NIFDE (4) that satisfies where and
Remark 11. satisfies inequality (48) if there exist function with (i) (ii)For all
Lemma 12. Let and is a solution of inequality (48). Then, satisfies where and
Proof. Let be a solution of (48).
By part (ii) of Remark 11, we have
Then, the solution of problem (52) is
Again by (i) of Remark 11, we obtain
Theorem 13. Under the assumptions of Theorem 8. Then, the solution of PC-NIFDE (4) is HU and GHU stable.
Proof. Let be a solution of inequality (48), and be a unique solution of the following PC-NIFDE.
From Lemma 12, we obtain where and Clearly, if then and Hence, (56) becomes
Using Lemma 12 and (Assu) for , we have
Using classical Gronwall’s Lemma [27], we obtain
For , we have
Using fractional Gronwall’s Lemma [27], we obtain
It follows from (59) and (61) that where
Hence, PC-NIFDE (4) is UH stable in . Moreover, if there exists a nondecreasing function, such that . Then, from (62), we have with which proves PC-NIFDE (4) is GUH stable in
4. Examples
In this portion, we present two examples to illustrate the reported results.
Example 1. Consider the following PC-NIFDE or where , and are positive constants with Set Let , . Then,
Hence, the condition () holds with Also we have
Hence, the condition () holds with . Moreover, the following condition
is satisfied with and Thus, with the assistance of Theorem 8, problem (65) has a unique solution . Further, since and then
and which implies that problem (65) is HU stable.
Example 2. Consider the following PC-NIFDE or where Set for and Let and . Then, Putting and Then, valid for any and . Also, Hence, and hold. Thus, all the assumptions of Theorem 7 are satisfied. Hence, problem (73) has a solution on .
5. Conclusions
Somewhat recently, numerous methodologies have been proposed to portray behaviors of some complex world problems emerging in numerous scholarly fields. One of these problems is the multistep behavior shown by certain problems. In this regard, Atangana and Araz [20] introduced the concept of piecewise derivative. As an extra contribution to this subject, existence, uniqueness, and UH stability results for PC-NIFDE (4) involving a piecewise Caputo FD have been obtained. Our approach to this work has been based on Banach’s and Schaefer’s fixed-point theorem and Gronwall’s Lemma. In light of our current results, the solution form for analogous problems containing piecewise Caputo-Fabrizio and Atangana–Baleanu operators have been presented. Finally, we have created two examples to validate the results obtained.
As an open problem, it will be very interesting to study the present problems on piecewise fractional operators with another function that is more general; precisely, one has to consider in problem (2) with such that where and are -Caputo FD of order introduced by Almeida [28]
Data Availability
No real data were used to support this study. The data used in this study are hypothetical.
Conflicts of Interest
No conflicts of interest are related to this work.
Acknowledgments
The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through large group research project under grant number R.G.P.2/204/43.