Abstract
In this paper, a new general identity for differentiable mappings via k-fractional integrals is derived. By using the concept of -convexity, -convexity and the obtained equation, some new trapezium-like integral inequalities are established. The results presented provide extensions of those given in earlier works.
Keywords: -convex functions; -convex functions; k-fractional integrals
Introduction
Let be a convex mapping and along with . The inequality
| 1.1 |
named Hermite-Hadamard’s inequality, is one of the most famous results for convex mappings. This inequality (1.1) is also known as trapezium inequality.
The trapezium-type inequality has remained an area of great interest due to its wide applications in the field of mathematical analysis. Many researchers generalized and extended it via mappings of different classes. For recent results, for example, see [1–7] and the references mentioned in these papers.
In 2013, Sarikaya et al. [8] established the following theorem by utilizing Riemann-Liouville fractional integrals.
Theorem 1.1
Let be a positive function along with , and let . Suppose that f is a convex function on , then the following inequalities for fractional integrals hold:
| 1.2 |
where the symbols and denote respectively the left-sided and right-sided Riemann-Liouville fractional integrals of order defined by
and
Here, is the gamma function and its definition is . It is to be noted that .
In the case of , the fractional integral recaptures the classical integral.
Because of the extensive application of Riemann-Liouville fractional integrals, some authors extended their studies to fractional trapezium-type inequalities via mappings of different classes. For example, refer to [9–12] for convex mappings, to [13] for s-convex mappings, to [14] for -convex mappings, to [15] for r-convex mappings, to [16] for harmonically convex mappings, to [17] for s-Godunova-Levin mappings, to [18, 19] for preinvex mappings, to [20] for MTm-preinvex mappings, to [21] for h-convex mappings and to references cited therein.
In [22], Mubeen and Habibullah introduced the following class of fractional derivatives.
Definition 1.1
([22])
Let , then k-Riemann-Liouville fractional derivatives and of order are given as
and
respectively, where and is the k-gamma function defined by . Furthermore, and .
The concept of k-Riemann-Liouville fractional integral is an important extension of Riemann-Liouville fractional integrals. We want to stress here that for the properties of k-Riemann-Liouville fractional integrals are quite dissimilar from those of general Riemann-Liouville fractional integrals. For this, the k-Riemann-Liouville fractional integrals have aroused the interest of many researchers. Properties concerning this operator can be sought out [23–26], and for the bounds for integral inequality related to this operator, the reader can refer to [27–29] and the references mentioned in these papers.
Motivated and inspired by the recent research in this field, we obtain some k-Riemann-Liouville fractional integral of trapezium-type inequalities for -convex mappings and -convex mappings. The results presented in this paper provide extensions of those given in earlier works.
To end this section, we restate some special functions and definitions.
- The beta function:
- The incomplete beta function:
Definition 1.2
([30])
The function is named -convex if, for every and , the following inequality holds:
where .
Definition 1.3
([31])
The function is called m-MT-convex if f is non-negative and, for all and , with , it satisfies the following inequality:
Definition 1.4
([32])
Let be a non-negative function. A function is said to be h-convex if f is non-negative and
holds for all and .
Definition 1.5
([33])
Let be a non-negative function. A function is said to be -convex if the inequality
holds for all and .
Definition 1.6
([34])
Let be a non-negative function. A function is named -convex if f is non-negative and
holds for all , and some fixed .
Clearly, when putting in Definition 1.6, f becomes an -convex function on as follows.
Definition 1.7
The function is named -convex if f is non-negative and
holds for all , and some fixed .
Note that, if we choose in Definition 1.7, f reduces to a -convex function in Definition 1.5.
A lemma
To prove our main results, we consider the following new lemma.
Lemma 2.1
Let be a differentiable mapping on (the interior of I) with , , for some fixed . If , then the following equality for k-fractional integral along with , and exists:
| 2.1 |
where
| 2.2 |
Proof
It suffices to note that
| 2.3 |
Integrating by parts, we get
| 2.4 |
Let , , equality (2.4) can be written as
| 2.5 |
and similarly we get
| 2.6 |
Hence, using (2.5) and (2.6) in (2.3), we can obtain the desired result. □
Corollary 2.1
In Lemma 2.1, for , we can get the result for Riemann-Liouville fractional integral.
Corollary 2.2
In Lemma 2.1, if we put , we get
| 2.7 |
Similarly, taking in Lemma 2.1, we obtain
| 2.8 |
Note that , it is easy to see that identity (2.8) is equal to identity (2.7).
Remark 2.1
k-fractional integral inequalities for -convex functions
In what follows, we establish some k-fractional integral inequalities for -convex functions by using Lemma 2.1.
Theorem 3.1
Let be a non-negative function, and let be a differentiable mapping on along with , , for some fixed . If and for is -convex on , then the following inequality exists:
| 3.1 |
where , and .
Proof
Case 1: . Applying Lemma 2.1 and the -convexity of , we have
where we use the fact that
and
By calculation,
Case 2: . Employing Lemma 2.1, the power mean inequality and the -convexity of leads to
This completes the proof. □
Now, we point out some special cases of Theorem 3.1.
Corollary 3.1
In Theorem 3.1, if we choose and , then we derive the following inequality for m-convex functions:
| 3.2 |
Especially if we put , we obtain Theorem 3.2 in [35].
Corollary 3.2
In Theorem 3.1, if we choose , and or , then we derive the following inequality for convex functions:
Remark 3.1
In Corollary 3.2,
Corollary 3.3
In Theorem 3.1, if we choose , , then we have the following inequality for -Breckner convex functions:
| 3.3 |
Especially if we choose and or , we can get Theorem 7 in [38].
Corollary 3.4
In Theorem 3.1, if we put , then we obtain the following inequality for -convex functions:
Especially if we choose and or , we have
Corollary 3.5
In Theorem 3.1, if we take , , then we get the following inequality for -Godunova-Liven-Dragomir convex functions:
Especially if we put and or , we get
Corollary 3.6
In Theorem 3.1, if we choose , then we obtain the following inequality for -convex functions:
Especially if we put and or , we get
Corollary 3.7
In Theorem 3.1, if we choose , then we obtain the following inequality for m-MT-convex functions:
Especially if we put and or , we get
Now, we prepare to introduce the second theorem as follows.
Theorem 3.2
Under the assumptions of Theorem 3.1, the resulting expression exists:
| 3.4 |
where , and .
Proof Using Lemma 2.1, Hölder’s inequality and the -convexity of , we have
Here, we use for any and .
Let us point out some special cases of Theorem 3.2.
Corollary 3.8
In Theorem 3.2, if we put , , then we get the following inequality for -Breckner convex functions:
Especially if we put and or , we have
Corollary 3.9
In Theorem 3.2, if we take , , then we get the following inequality for -Godunova-Levin-Dragomir convex functions:
Especially if we take and or , we have
Corollary 3.10
In Theorem 3.2, if we put , then we get the following inequality for -convex functions:
Especially if we put and or , we have
Corollary 3.11
In Theorem 3.2, if we put , then we get the following inequality for m-MT-convex functions:
Especially if we put and or , we have
Now, we are ready to state the third theorem in this section.
Theorem 3.3
Let be a non-negative function, and let be a differentiable mapping on along with , , for some fixed . If and for is -convex on , then the following inequality holds:
| 3.5 |
where , , and .
Proof
Applying Lemma 2.1, Hölder’s inequality and the -convexity of , we have
Here, we use the fact that for any and , which completes the proof. □
Now, we point out some special cases of Theorem 3.3.
Corollary 3.12
In Theorem 3.3, if we choose and , then we obtain the following inequality for m-convex functions:
Especially if we put , we obtain Theorem 3.3 in [35]. Further, if we put , we obtain Theorem 2.6 in [12].
Corollary 3.13
In Theorem 3.3, if we choose , and or , then we obtain the following inequality for convex functions:
Remark 3.2
In Corollary 3.13,
Corollary 3.14
In Theorem 3.3, if we choose , , then we obtain the following inequality for -Breckner convex functions:
Especially if we put and or , then we have
Corollary 3.15
In Theorem 3.3, if we put , then we obtain the following inequality for -convex functions:
Especially if we put and or , we have
Corollary 3.16
In Theorem 3.3, if we take , , then we obtain the following inequality for -Godunova-Levin-Dragomir convex functions:
Especially if we take and or , we have
Corollary 3.17
In Theorem 3.3, if we put , then we obtain the following inequality for m-MT-convex functions:
Especially if we put and or , we have
Corollary 3.18
In Theorem 3.3, if we choose , then we obtain the following inequality for -convex functions:
Especially if we choose and or , we have
k-fractional inequalities for -convex functions
Using Lemma 2.1 again, we state the following theorems.
Theorem 4.1
Let be a differentiable mapping on along with and . If for is -convex on and . Then the following inequality for k-fractional integrals holds:
| 4.1 |
where , and .
Proof
Using Lemma 2.1, the power mean inequality and the -convexity of , we have
which completes the proof. □
Theorem 4.2
Under the assumptions of Theorem 4.1, the following inequality for k-fractional integrals holds:
| 4.2 |
where , and .
Proof
By making use of Lemma 2.1, Hölder’s inequality and the -convexity of , we get
Here, we use for any and . This ends the proof. □
Theorem 4.3
Let be a differentiable mapping on along with and . If for is -convex on and , then the following inequality for k-Riemann-Liouville fractional integral holds:
| 4.3 |
where , , and .
Proof
Employing Lemma 2.1, Hölder’s inequality and the -convexity of , we have
where we use the fact that for any and . This completes the proof. □
Remark 4.1
If we take or , we can deduce some new k-fractional integral trapezium-like inequalities from the results of Theorems 4.1, 4.2 and 4.3 and their related inequalities.
Acknowledgements
This work was partially supported by the National Natural Science Foundation of China under Grant No. 61374028.
Authors’ contributions
All authors contributed equally to the writing of this paper. All authors read and approved the final manuscript.
Competing interests
The authors declare that they have no competing interests.
Footnotes
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Contributor Information
Hao Wang, Email: haowangctgu@163.com.
Tingsong Du, Email: tingsongdu@ctgu.edu.cn.
Yao Zhang, Email: yaozhangctgu@gmail.com.
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