Abstract

The class of exponentially -convex functions has been discovered to unify different kinds of convexities. This paper finds new Riemann–Liouville fractional Hadamard-type inequalities for this generalized class of convex functions. These results further have their consequences which are presented in the form of corollaries. Moreover, some known results are identified in the form of remarks.

1. Introduction

Fractional calculus has opened a new era in the theoretic and application point of view. Many subjects of science and engineering get wonderful advancements in modeling and solving complex systems with the help of fractional integral and derivative operators. Besides making advancements in other fields, fractional integral and derivative operators have been proved very useful in generalizing and extending mathematical inequalities. In this paper, we will extend the Hadamard-type inequalities for Riemann–Liouville (RL) fractional integral operators.

Definition 1. Let . The left and right RL fractional integrals and of order , , of are defined byrespectively, where is the Euler’s gamma function and .
The -analogue RL fractional integral operators are studied by Mubeen and Habibullah in [1].

Definition 2. Let . The left and right RL -fractional integrals and of order , of are defined bywhere is the -gamma function and .
Fractional integral inequalities are generalizations of classical inequalities which play a key role in the solutions and their uniqueness in fractional boundary value problems. The Hadamard inequality is one of the classical inequalities for convex functions, and it has been studied by a lot of researchers for different kinds of fractional integral and derivative operators, see [211] and references therein. It is stated in the undermentioned theorem.

Theorem 1 (see [11]). If is a convex function on the interval of real numbers and with then

Definition 3. A function , where is an interval in , is said to be convex function ifholds for all and .
The Hadamard inequality is the geometric interpretation of convex functions which has been analyzed by many researchers for fractional integral and differentiation operators. The objective of this paper is to obtain -fractional integral inequalities for a generalized class of convex functions, namely, exponentially -convex functions. Convex functions proved very useful for the establishment of very known and vital inequalities. An important and significant generalization of convex functions is exponentially -convex functions. It is defined by He et al. in [12] as follows.

Definition 4. Let be an interval containing and let be a nonnegative function. A function is called an exponentially -convex function, if is nonnegative, and for all , , , and , one has

Remark 1. By selecting a suitable function and a particular value of parameters and , the above definition produces the functions comprised in the following remarks:(i)By setting , -convex function [4] can be obtained(ii)By setting and , -convex function [13] can be obtained(iii)By setting and , -convex function [14] can be obtained(iv)By setting , and , -convex function [15] can be obtained(v)By setting , , and , -convex function [16] can be obtained(vi)By setting , , , and , convex function [17] can be obtained(vii)By setting , , , and , -function [18] can be obtained(viii)By setting and , exponentially -convex function [19] can be obtained(ix)By setting , , and , exponentially -convex function [20] can be obtained(x)By setting and , exponentially -convex function [21] can be obtained(xi)By setting , , and , exponentially convex function [22] can be obtained(xii)By setting , , and , -convex function [23] can be obtained(xiii)By setting , , , and , -convex function [20] can be obtained(xiv)By setting , , , and , Godunova–Levin function [24] can be obtained(xv)By setting , , , and , -Godunova–Levin function of the second kind [25] can be obtainedThe article is organized in the following manner: in Section 2, we prove the -fractional integral inequality of Hadamard type for exponentially -convex functions and deduce some related results. In section 3, we prove a version of the -fractional integral inequality of Hadamard type for differentiable function so that is exponentially -convex. In section 4, we prove the -fractional integral inequality of Hadamard type for the product of two exponentially -convex functions.

2. Main Results

First, we give a -fractional integral inequality for exponentially -convex functions as follows.

Theorem 2. Let be an exponentially -convex function with , also let , . Then, we will havewhere , and .

Proof. Since is exponentially -convex on , for , we havefrom which multiplying both sides with and integrating over , we will haveBy changing variables, we will haveThis completes the proof of first inequality in (6). The second inequality in (6) follows by using Holder’s inequality:Thus from (9), we will get (6).

Some special cases of the above theorem are discussed in the following corollaries.

Corollary 1. The following inequality holds for an exponentially -convex function via an RL fractional integral by setting in inequality (6):

Corollary 2. The following inequality holds for the -convex function via an RL -fractional integral by setting in inequality (6):

Corollary 3. The following inequality holds for the -convex functions via RL -fractional integrals by setting and in inequality (6):

Corollary 4. The following inequality holds for the -convex function via RL fractional integrals by setting , , , and in inequality (6):The next two special cases are already proved in [26].

Corollary 5. The following inequality holds for the exponentially -convex function via RL -fractional integrals:

Proof. By setting and in inequality (6) of Theorem 2, we get the above inequality (15) which is given in [26] (Theorem 1).

Corollary 6. The following inequality holds for the -convex function via RL -fractional integrals:

Proof. By setting , , and in inequality (6) of Theorem 2, we get the above inequality (16) which is given in [26] (Theorem 4). □
The next result holds for exponentially -convex functions, whereas the function is superadditive.

Theorem 3. Let be exponentially -convex functions with , also let be superadditive and , . Then, for RL -fractional integrals, we have

Proof. Since is an exponentially -convex function on , for , we getsince is superadditive; therefore,By multiplying both sides of the above inequality with and integrating over , we will haveBy substituting in the left side of the above inequality, it leads to (17).

Some special cases are given in the form of following corollaries.

Corollary 7. The following inequality holds for the exponentially -convex function via RL fractional integrals by setting in inequality (17):

Corollary 8. The following inequality holds for the -convex function via RL -fractional integrals by setting in inequality (17):

Corollary 9. The following inequality holds for -convex functions via RL -fractional integrals:

Proof. By setting and in inequality (17) of Theorem 3, we get the above inequality (22) which is given in [4] (Theorem 2.6).

3. Fractional Hadamard-Type Inequalities for Functions Whose Derivatives in Absolute Values are Exponentially -Convex

In the following, -fractional integral inequalities of Hadamard type for exponentially -convex functions in terms of the first derivatives have been obtained. For the next result, we use the following lemma.

Lemma 1 (see [4]). Let be a differentiable mapping on the interval with . If , then for -fractional integrals, we will have

Theorem 4. Let be a function such that and . If is exponentially -convex functions with and , . Then, for RL -fractional integrals, we havewhere .

Proof. By using the property of modulus from Lemma 1, we will getBy exponentially -convexity of , we haveNow, by using Holder inequality in the right-hand side of (27), we will getBy some manipulation, one can get inequality (25).

Corollary 10. The following inequality holds for the exponentially -convex function via RL fractional integrals by setting in inequality (25):

Corollary 11. The following inequality holds for the -convex function via RL -fractional integrals by setting in inequality (25):

The following special cases are proved in [4, 26].

Corollary 12. The following inequality holds for the -convex function via RL -fractional integrals:

Proof. By setting and in inequality (25) of Theorem 4, we get the above inequality (31) which is given in [4] (Theorem 3.6).

Corollary 13. The following inequality holds for the exponentially -convex function via RL -fractional integrals:

Proof. By setting and in inequality (25) of Theorem 4, we get the above inequality (32) which is given in [26] (Theorem 2).

Corollary 14. The following inequality holds for the exponentially -convex function via RL -fractional integrals:

Proof. By setting , , and in inequality (25) of Theorem 4, we get the above inequality (33) which is given in [26] (Theorem 5).

4. Fractional Hadamard-Type Inequalities for Product of Two Exponentially -Convex Functions

Now, we obtain some Hadamard-type inequalities for the product of two exponentially -convex functions via RL -fractional integrals.

Theorem 5. Let be functions such that , . If function is exponentially -convex and function is exponentially -convex on with , then the following inequalities hold for RL -fractional integrals:where and .

Proof. Since function is exponentially -convex and function is exponentially -convex, for , we haveby multiplying both sides of the above inequality with and integrating over , we haveBy substituting in the left-hand side of the above inequality, we getBy using Holder inequality, we will haveThus, we will getSimilarly, by changing the roles of and , after a little computation, one can getAdding (39) and (40), we get the required result.

Corollary 15. The following inequality holds for the exponentially -convex function via RL fractional integrals:

Proof. By setting in inequality (34) of Theorem 5, we get the above inequality (41).

Corollary 16. The following inequality holds for the -convex function via RL -fractional integrals:

Proof. By setting in inequality (34) of Theorem 5, we get the above inequality (42).

Corollary 17. The following inequality holds for the -convex function via RL -fractional integrals:

Proof. By setting and in inequality (34) of Theorem 5, we get the above inequality (43) which is given in [4] (Theorem 4.3).

Corollary 18. The following inequality holds for the exponentially -convex function via RL -fractional integrals:

Proof. By setting and in inequality (34) of Theorem 5, we get the above inequality (44) which is given in [26] (Theorem 3).

Corollary 19. The following inequality holds for the -convex function via RL -fractional integrals:

Proof. By setting , , and in inequality (34) of Theorem 5, we get the above inequality (45) which is given in [26] (Theorem 6).

Theorem 6. Let be functions such that , . If function is exponentially -convex and function is exponentially -convex on with , then the following inequalities hold for RL -fractional integrals:

Proof. Since function is exponentially -convex and function is exponentially -convex, then for , we haveBy multiplying both sides of the above inequality with and integrating over , we haveBy substituting in the left-hand side of the above inequality, we getSimilarly, by changing the rules of and , after a little computation, one can getAdding (49) and (50), we get the required result.

Corollary 20. The following inequality holds for the exponentially -convex function via RL fractional integrals:

Proof. By setting in inequality (49) of Theorem 6, we get the above inequality (51).

Corollary 21. The following inequality holds for the -convex function via RL -fractional integrals:

Proof. By setting in inequality (49) of Theorem 6, we get the above inequality (52) which is given in [4] (Theorem 4.6).

Corollary 22. The following inequality holds for the -convex function via RL fractional integrals:and

Proof. From (49) by setting , , and , we get (53). Similarly, using , , and in (50), we get (54) which is given in [27] (Theorem 12).

Data Availability

No data were used in this study.

Conflicts of Interest

The authors declare that there are no conflicts of interest regarding the publication of this article.

Acknowledgments

The research work of Ghulam Farid was supported by the Higher Education Commission of Pakistan with Project no. 5421.