1. Introduction
It is well known that extensive literature on the class of integral inequalities is being introduced under various notions of convexity; see, for instance [
1,
2,
3,
4,
5,
6]. Inspired by the importance of convexity in multiple fields of pure and applied sciences, researchers generalized and extended the notion of convexity in various settings. A useful generalization of convex functions is introduced by Hanson [
7] which is called invex functions. In 1986, Ben-Israel and Mond [
8] proposed the notion of preinvex functions and showed that every differentiable preinvex function is invex, but the converse may not be true. Yang and Li [
9] provided two conditions that determine the preinvexity of a function via an intermediate-point preinvexity check under conditions of upper and lower semicontinuity, respectively.
On the other hand, interval analysis was introduced to handle interval uncertainty in many mathematical or computer models of some deterministic real-world phenomena. Moore [
10] was the first to propose the concept of interval analysis and extend the arithmetic of intervals to the computer. Moore et al. [
11] discussed an arithmetic for intervals, integration of interval functions, and interval Newton methods. Bhurjee and Panda [
12] provided a methodology to determine the efficient solution of general multi-objective interval fractional programming problem. Lupulescu [
13] gave a theory of the fractional calculus for interval-valued functions using gH-difference for closed intervals. Further, Li et al. [
14] introduced the concept of invexity using gH-derivative of interval-valued functions and derived Kuhn–Tucker optimality conditions for an interval-valued objective function. Interval analysis has applications in various fields such as experimental and computational physics, error analysis, computer graphics, robotics, numerical integration, and many other fields (see [
15,
16,
17,
18,
19]).
2. Literature Survey
Işcan [
20] proposed the concept of harmonically convex functions and presented some Hermite–Hadamard (H–H)-type inequalities for harmonically convex functions. Noor et al. [
21] defined a new class of preinvex functions named h-preinvex functions and established H–H-type inequalities for these preinvex functions under certain conditions. Further, Noor et al. [
22] introduced harmonic
h-preinvex function and obtained Ostrowski type inequalities for harmonic
h-preinvex functions using Riemann–Liouville (R–L) fractional integrals. In recent years, several integral inequalities for different type of preinvex functions are investigated by many authors; see, for instance [
23,
24,
25,
26,
27,
28,
29,
30].
Cano et al. [
31] obtained some Ostrowski type inequalities for interval-valued functions using gH-derivative. Zhao et al. [
32] investigated Riemann interval delta integrals for interval-valued functions on time scales and proved Jensen’s, Hölder’s, and Minkowski’s inequalities using Riemann interval delta integrals. Budak et al. [
33] defined right-sided R–L fractional integrals for interval-valued functions and obtained H–H-type inequalities for interval-valued R–L fractional integrals. Lou et al. [
34] presented the notions of the Iq-integral and Iq-derivative and gave the Iq-H–H inequalities for interval-valued functions. Further, numerous concepts of quantum calculus for interval-valued functions have been investigated by [
35,
36,
37].
Considering the importance of interval analysis, many researchers established relations between integral inequalities and different types of interval-valued functions. Zhao et al. [
38] introduced the notion of harmonical
h-convexity for interval-valued functions and proved some new H–H-type inequalities for the interval Riemann integral. Further, Zhao et al. [
39,
40] introduced the concept of interval-valued coordinated convexity and established H–H-type inequalities for newly defined interval-valued coordinated convex functions. Recently, Sharma et al. [
41] introduced
-preinvex interval-valued function and derived fractional H–H-type inequalities for these class of interval-valued preinvex functions. Zhou et al. [
42] derived H–H-type inequalities for interval-valued exponential type preinvex functions for R–L interval-valued fractional operator. For more inequalities for interval-valued functions, see references [
43,
44,
45,
46,
47,
48,
49].
The work in this paper is mainly motivated by Zhao et al. [
38] and Shi et al. [
50]. We propose the concept of harmonically
h-preinvex interval-valued function which includes harmonical
h-convex interval-valued functions as a special case. We prove new fractional inclusions of H–H-type for harmonically
h-preinvex interval-valued functions. We also present H–H-type inclusions for the product of two harmonically
h-preinvex interval-valued functions for interval-valued R–L fractional integrals. Further, we discuss some special cases of our main results. The results obtained in this paper may be generalized for other kinds of interval-valued fractional integrals including harmonically h-preinvex interval-valued functions. As future directions, we can investigate the interval-valued preinvexity on coordinates and establish new inclusions of H–H-type for interval-valued coordinated preinvex functions.
The presentation sequence of the proposed work is the following. In
Section 3, we consider some basic definitions and notions of interval analysis. Additionally, we discuss the related results required for this paper. In
Section 4, we define harmonically
h-preinvexity of interval-valued functions and prove fractional H–H-type inclusions for harmonically
h-preinvex interval-valued functions. Some special cases of these results are also discussed in
Section 4. In
Section 5, we discuss the results obtained by us in this paper. Finally, in
Section 6, conclusions and future directions of this study are given.
3. Preliminaries
Let be the collection of all closed intervals of and . Then, interval is defined by:
We say
is positive if
or negative if
. We denote the set of all positive closed intervals by
and the set of all negative closed intervals by
The following binary operations for intervals
and
are given by [
17].
where
Definition 1 ([17]).A function ψ is called an interval-valued function on if it assigns a nonempty interval to each andwhere and are real-valued functions. Theorem 1 ([11]).Let be an interval-valued function such that Then, ψ is interval Riemann integrable (integrable) on if and only if and are Riemann integrable (integrable) on and The collection of all R-integrable and -integrable functions on denoted by and , respectively.
Definition 2 ([51]).Let . The R–L fractional integrals and of order with are defined byandrespectively. Here, is the Gamma function defined by Definition 3 ([13,33]).Let be an interval-valued function and The interval-valued R–L fractional integrals of function ψ are defined byandwhere is the Gamma function. Corollary 1 ([33]).If is an interval-valued function such that with then we haveand Definition 4 ([52]).A set is called a harmonic convex set if Definition 5 ([20]).A function is called harmonic convex, if Now we consider some concepts for harmonic preinvex functions. Let and be continuous functions.
Definition 6 ([53]).A set is called a harmonic invex with respect to , if It is well known that every harmonic convex set is harmonic invex with respect to but not conversely.
Definition 7 ([53]).A function is said to be harmonic preinvex with respect to the bifunction , if Condition C [
54]. Let
be an invex set with respect to
. Then, function
holds the condition C if for any
and any
,
Note that
and from condition C, we have
Theorem 2 ([55]).Let be a preinvex function on I and with . Thenwhich is called the H–H-Noor inequality. Definition 8 ([41]).If is an invex set with respect to is an interval-valued function on Then ψ is preinvex interval-valued function on I with respect to if 4. Main Results
In this section, first, we define harmonically h-preinvex interval-valued function and discuss some special cases of harmonically h-preinvex interval-valued function.
Definition 9. Let be a non-negative function such that h 0, and be a harmonic invex set with respect to . Let be an interval-valued function on set I, then ψ is called harmonically h-preinvex interval-valued function with respect to if Now, we consider some special cases of harmonically h-preinvex interval- valued functions.
For function is called a harmonically preinvex interval-valued function.
For function is called a harmonically preinvex interval-valued function.
If , then we find the definition of Breckner type of harmonically preinvex interval-valued functions.
If , then we find the definition of Godunova–Levin type of harmonically preinvex interval-valued functions.
Example 1. Let , then ψ is harmonically h-preinvex interval-valued function on I.
Now, we establish fractional inclusion of H–H for harmonically h-preinvex interval-valued functions.
Theorem 3. Let be a non-negative function such that . Let be a harmonically h-preinvex interval-valued function such that and with If , and η holds condition C, thenwhere and is defined by Proof. As
is harmonically
h-preinvex interval-valued function on
, we have
Let
and
. Then, using Condition
C in (
1), we find
Multiplying (
2) by
and integrating over
with respect to
t, we have
Applying Theorem 1 in above relation, we find
Using (
4)–(
6) in (
3), we have
As
is an harmonically
h-preinvex interval-valued function on
we have
and
Adding (
8) and (
9), we have
Multiplying (
10) by
and integrating over
with respect to
we have
From (
7) and (
11), we find
□
Example 2. Let . Let and ∀,
be defined by From (12)–(14), we see Theorem 3 is verified. Remark 1. If we put in the above theorem, we obtain Theorem 5 of [50]. Remark 2. If we put and in the above theorem, we obtain Theorem 1 of [38]. Remark 3. If we put and in the above theorem, we obtain Theorem 3.6 of [56]. Now we present some particular cases of Theorem 3.
Corollary 2. If then Theorem 3 gives the following result: Corollary 3. If then Theorem 3 gives the following result: Next, we prove fractional inclusions of H–H-type for the product of two harmonically h-preinvex interval-valued functions.
Theorem 4. Let be non-negative functions and . Let be two harmonically - and -preinvex interval-valued functions, respectively, such that , and with If , and η holds condition C, thenwhere and .
Proof. As
and
are two harmonically
- and
-preinvex interval-valued functions on
respectively. Therefore,
and
As
then from (
16) and (
17), we obtain
Adding (
18) and (
19), we have
Multiplying (
20) by
and integrating over
with respect to
t, we have
Using (
22), (
23) in (
21), we have
□
Remark 4. If we put in the above theorem, we obtain Theorem 6 of [50]. Remark 5. If we put and in the above theorem, we obtain Theorem 3 of [38]. Corollary 4. If then Theorem 4 gives the following result: Corollary 5. If then Theorem 4 gives the following result: Theorem 5. Let be non-negative functions and . Let be two harmonically - and -preinvex interval-valued functions, respectively, such that , and with If , and η holds condition C, thenwhere and are defined as previous. Proof. As
is harmonically
-preinvex interval-valued function on
, we have
Let
and
. Then, using Condition
C in (
24), we find
From (
25) and (
26), we find
As
and
are two harmonically
- and
- preinvex interval-valued functions, respectively. Therefore,
Adding (
28) and (
29), we obtain
From (
27) and (
30), we have
Multiplying (
31) by
, then integrating over
with respect to
t, we find
□
Remark 6. If we put in the above theorem, we obtain Theorem 7 of [50]. Remark 7. If we put and in the above theorem, we obtain Theorem 4 of [38]. Corollary 6. If then Theorem 5 gives the following result: Corollary 7. If then Theorem 5 gives the following result: 5. Results and Discussions
After illustrating the concept of interval-valued functions, this paper proposes a new definition of harmonically
h-preinvex interval-valued functions. Further, with the help of the proposed harmonically
h-preinvexity for interval-valued functions, we have proven H–H-type inclusions for interval-valued R–L fractional integrals. From the definition of harmonically
h-preinvex interval-valued function, we can see that every harmonical
h-convex interval-valued function is harmonically
h-preinvex interval-valued function with respect to
. The results obtained in this paper are generalization of the results of Zhao et al. [
38] and Shi et al. [
50]. Moreover, some particular cases of our main outcomes are considered.
6. Conclusions and Future Directions
In this paper, we have introduced harmonically h-preinvex interval-valued functions which include harmonical h-convex interval-valued functions and harmonical convex interval-valued functions as special cases. We have obtained H–H-type fractional inclusions for harmonically h-preinvex interval-valued functions. After that, we have proven fractional H–H-type inclusions for the product of two harmonically h-preinvex interval-valued functions. The results obtained in this paper may be extended for other kinds of interval-valued fractional integrals including harmonically h-preinvex interval-valued functions. In the future, we can investigate the interval-valued preinvexity on coordinates and establish new inclusions of H–H-type for interval-valued coordinated preinvex functions. It is expected that current work will motivate researchers working in fractional calculus, interval analysis, and other related areas.
Author Contributions
Formal analysis, K.K.L., J.B., N.S. and S.K.M.; funding acquisition, K.K.L.; investigation, S.K.M.; methodology, J.B., N.S. and S.K.M.; supervision, S.K.M.; validation, N.S.; writing—original draft, J.B.; writing—review and editing, K.K.L., J.B. and N.S. All authors have read and agreed to the published version of the manuscript.
Funding
Second author is financially supported by the Ministry of Science and Technology, Department of Science and Technology, New Delhi, India, through Registration No. DST/INSPIRE Fellowship/[IF190355] and the fourth author is financially supported by “Research Grant for Faculty” (IoE Scheme) under Dev. Scheme NO. 6031 and Department of Science and Technology, SERB, New Delhi, India through grant no.: MTR/2018/000121.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
No data were used to support this study.
Acknowledgments
The authors are indebted to the anonymous reviewers for their valuable comments and remarks that helped to improve the presentation and quality of the manuscript.
Conflicts of Interest
The authors declare no conflict of interest.
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