Abstract
In this paper, we establish a new version of Hermite-Hadamard-Fejér type inequality for harmonically convex functions in the form of weighted fractional integral. Secondly, an integral identity and some weighted midpoint fractional Hermite-Hadamard-Fejér type integral inequalities for harmonically convex functions by involving a positive weighted symmetric functions have been obtained. As shown, all of the resulting inequalities generalize several well-known inequalities, including classical and Riemann–Liouville fractional integral inequalities.
1. Introduction
The theory of convex functions is an essential tool in various fields of pure and applied sciences. There is also a close connection between the theory of convex functions, the theory of inequalities, and fractional differential equations. At the same time, fractional differential equations are one of the most studied fields of mathematics due to their application in the real world. Many inequalities are proved for convex functions but, the most known from the related literature is Hermite-Hadamard inequality.
A function on an interval of real line is said to be convex, if for all and , then
The Hermite-Hadamard integral inequality is a well-known inequality in the subject of convex functional analysis. It has an interesting geometric representation with numerous important applications. The extraordinary inequality states that if is a convex mapping on the interval I of real numbers and with then
Inequality (2) was introduced by C. Hermite [1] and investigated by J. Hadamard [2] in 1893. Both inequalities hold in the inverted direction if is concave. Many mathematicians have paid considerable attention to Hermite-Hadamard inequality due to its quality and integrity in mathematical inequality. For significant developments, modifications, and consequences regarding the Hermite-Hadamard uniqueness property and general convex function definitions, for essential details, the interested reader would like to refer to [3,4,5,6,7] and references therein. Fractional calculus and applications have application areas in many different fields such as physics, chemistry and engineering, and mathematics. Applying arithmetic in classical analysis in the fractional analysis is very important in obtaining more realistic results in solving many problems. Many real dynamical systems are better characterized using non-integer order dynamic models based on fractional computation. While integer orders are a model that is not suitable for nature in classical analysis, fractional computation in which arbitrary orders are examined enables us to obtain more realistic approaches. Regarding some papers dealing with fractional integral inequalities via different types of fractional integral operators, we refer readers to [8,9,10,11,12,13,14,15,16].
Furthermore, Sarikaya et al. [17] generalized and reformed the Hermite-Hadamard integral inequality (2) in forms of Riemann–Liouville fractional integrals in 2013.
where the function with and . Therefore, is left-sided Riemann–Liouville fractional integrals and is the right-sided Riemann–Liouville fractional integrals with order , defined by [18]
respectively. Here, is the Gamma function and
Due to the use of the interval’s ends , the inequality (3) is called endpoint Hermite-Hadamard inequality.
The midpoint Hermite-Hadamard inequality was discovered by Sarikaya and Yildirim [19] after expending the essential area of the integral inequalities in (2) and (3)
where the function is convex and continuous. In [20], I. G. Macdonald gave the following definition.
Definition 1.
Suppose that a function and it is symmetric with respect to if
Fejér proposed the following generalization of Hadamard inequality in 1906 (see [21]):
Theorem 1.
Let be a convex function such that . Furthermore, let be a positive, integrable and symmetric to . Then the following inequality holds:
The inequality (6) is well-known as the Fejér-Hadamard inequality in the literature.
In the concept of Riemann–Liouville fractional integrals, İ. İşcan [22] discovered the endpoint version of (6), which is also the extension of (3). As a result, the final inequalities are shown as follows:
where is convex and continuous, is symmetric and belongs to (see Definition 1).
In [23], İ. İşcan gave definition of harmonically convex functions and established following Hermite-Hadamard type inequality for harmonically convex functions as follows:
Definition 2.
Let be an interval of nonzero real numbers. Then a function is said to be harmonically convex if
holds for all and .
In [24], Latif et al. gave the following definition.
Definition 3.
A function is said to be harmonically symmetric with respect to if
İşcan et al. published Hermite-inequality Hadamard’s in fractional integral type for harmonically convex functions In [22], as follows:
Theorem 2.
Let be a harmonically convex function and with . If then the following inequalities holds:
Hermite-Hadamard inequalities for harmonically convex functions were introduced in fractional integral form in [25] as follows:
Theorem 3.
Consider a function such that , where with . If is a harmonically convex function on , then
with and where
For harmonically convex functions, in [17] Chan et al. stated the Hermite-Hadamard-Fejér inequality as follows:
Theorem 4.
Suppose that harmonically convex function . If and is positive, an integrable, and harmonically symmetric with respect to then
and with
In [26], İşcan et al. proved Hermite-Hadamard-Fejér type inequalities for harmonically convex functions through fractional integrals:
Theorem 5.
Let be a harmonically convex function and with . If and is positive, an integrable, and harmonically symmetric with respect to then
with and
In [27], Fahad et al. presented weighted fractional integrals as follows:
Definition 4.
Let and be an increasing positive and monotone function on the interval with a continuous derivative on the open interval . Then the weighted fractional integrals on the left and right sides of a function according to another function on are shown as below:
with and for with
Remark 1.
with
Using Definition 4, we have
- (i)
- Equation (12) can be restated in the following form: If with , then the weighted fractional integrals reduce to the classical Riemann–Liouville fractional integrals.
- (ii)
- Putting , so we obtain the fractional integrals of with regard to the function for more details see [28,29]:
We recall the following special functions which are known as Beta and hypergeometric function
respectively, (see [18]).
The polygamma function of order m is a meromorphic function on the complex numbers defined as the th derivative of the logarithm of the gamma function:
Thus
holds where is the digamma function and is the gamma function.
When and , the integral representation of polygamma is given by
The generalized hypergeometric function is given by a hypergeometric series, i.e., a series for which the ratio of successive terms can be written as
The resulting generalized hypergeometric function is written
where and is the Pochhammer symbol or rising factorial defined by
In this article, we will use fractional weighted integrals (12) with nonnegative symmetric weighted functions in the kernel, necessary and auxiliary lemmas to study Hermite-Hadamard-Fejér type inequalities in Section 2. We shall prove our key results in Section 3, which will include new midpoint fractional Hermite-Hadamard-Fejér type integral inequalities as well as some related results. The conclusion will be presented in Section 4.
2. Auxiliary Results
Lemma 1.
If is integrable and harmonically symmetric with respect to , then
- (i)
- for each , we have
- (ii)
- For , we haveand
Proof.
□
Theorem 6.
Let , let be an harmonically convex function and is nonnegative, an integrable, and symmetric weighted function with respect to . If σ is is an increasing and positive function from onto itself such that its derivative is continuous on for , then
Proof.
Since is a harmonically convex function on , we write
Therefore, for and , it follows
Multiplying both sides of (17) by and integrating the resulting inequality with respect to over , we obtain
It follows that
We can demonstrate that by calculating the weighted fractional operators,
so,
Setting and , one can deduce that
As a consequence,
As a result, left inequality of (18) has been proven.
The second inequality of (18) can be proved using the harmonically convex function of .
Multiplying both sides of (23) by and we obtain by integrating the resulting inequality in terms of on .
This ends our proof. □
Remark 2.
We can derive the following special results from Theorem 6:
Lemma 2.
Let , let be a continuous with a derivative such that and let is nonnegative, an integrable, positive, and symmetric weighted function with respect to . If σ is an increasing and positive function from onto itself such that its derivative is continuous on , for then, we have
3. Main Results
We can conclude the following Hermite-Hadamard-Fejér inequalities with the help of Lemma 2.
Theorem 7.
Suppose that all the conditions of Lemma 2 and is harmonically convex on and σ is an increasing and positive function from onto itself such that its derivative is continuous on , for then we have
where and are defined as follows:
and
Proof.
Using the Lemma 2 as well as properties of the modulus and the harmonically convex function of , we get
Since is harmonic-convex on , where
Consequently, we obtain
where
and
Using the above calculations, we obtain the following integral
Theorem 8.
Suppose that all the conditions of Lemma 2 andis harmonically convex on with and σ is an increasing and positive function from onto itself such that its derivative is continuous on , for , then we have
where and are defined in Theorem 7.
Proof.
Using the Lemma 2 as well as properties of power mean inequality and the harmonically convex function of , we get
Since is harmonic-convex on , where
As a result, we get
where it is obvious that
Theorem 9.
Suppose that all the conditions of Lemma 2 and is harmonically convex on with and σ is an increasing and positive function from onto itself such that its derivative is continuous on , for , then we have
where and are defined as follows:
and
Proof.
Using the Lemma 2 as well as properties of well-known Hölder’s inequality and the harmonically convex function of , we have
Since is harmonic-convex on , where
As a result, we get
where it is obvious
4. Conclusions
In this paper, inequalities of the Hermite-Hadamard-Fejér type for harmonically convex functions in fractional integral forms are given in this study. Using weighted fractional integrals with positive weighted symmetric function kernels, an integral identity and various midpoint fractional Hermite-Hadamard-Fejér type integral inequalities for harmonically convex functions are also found.
Author Contributions
Writing—original draft, H.K.; Writing—review and editing, H.K. and H.A.; Formal analysis, H.A. and M.A.L.; software, H.K. and M.V.-C.; Methodology, H.A.; Validation, M.V.-C.; Funding acquisition, M.V.-C.; Supervision, M.A.L. All authors have read and agreed to the published version of the manuscript.
Funding
Department of Mathematics, Zhejiang Normal University, Jinhua, 321004, China.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Acknowledgments
The Chinese Government is to be acknowledged for providing postdoctoral studies to Humaira Kalsoom. We want to give thanks to the Dirección de investigación from Pontificia Universidad Católica del Ecuador for technical support to our research project entitled: Algunas desigualdades integrales para funciones convexas generalizadas y aplicaciones.
Conflicts of Interest
The authors declare no conflict of interest.
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