Abstract
In this study, we present new variants of the Hermite–Hadamard inequality via non-conformable fractional integrals. These inequalities are proven for convex functions and differentiable functions whose derivatives in absolute value are generally convex. Our main results are established using the classical Jensen–Mercer inequality and its variants for -convex modified functions proven in this paper. In addition to showing that our results support previously known results from the literature, we provide examples of their application.
Keywords:
convex functions; (h,m)-convex functions; Jensen–Mercer inequality; Hermite–Hadamard inequality; Hölder inequality; power mean inequality; non-conformable fractional operators MSC:
26A33; 26A51; 26D15
1. Introduction
Jensen’s inequality is one of the most studied results in the literature. In the last few decades, quite a few researchers have been interested in refining and generalizing this inequality (see, e.g., [1,2,3,4,5,6]).
Let and let () be positive weights associated with these and let their sum demonstrate unity. Then, Jensen’s inequality
holds (see [7]).
Mercer investigated a generalized form of Jensen’s inequality, which is famously known as the Jensen–Mercer inequality (see [8]): if is a convex function on , then
is fulfilled for , with . In case of , inequality (2) reads as
for . Extensions of this result can be found in e.g., [9,10,11].
The well-known refinement of Jensen’s inequality, the Hermite–Hadamard inequality
for convex functions, was proved by Hermite in 1883 and independently by Hadamard in 1893; see, e.g., [12]. This inequality has been generalized by many researchers, taking into account various aspects such as general convexity and fractional operators. For Hermite–Hadamard–Mercer type results, see [13,14,15,16,17,18].
In general, the concept of convex and general convex functions plays a major role in the theory of integral inequalities. So far, many general convex classes have been described in the literature. A summary of many of these classes was given in [19].
Definition 1.
Let , and . If inequality
is fulfilled and , where , then function Φ is called -convex on I.
In [20,21], the following definitions were presented.
Definition 2.
Let and . If inequality
is fulfilled and , where , , then function Φ is called -convex modified of the first type on I and this set of functions will be denoted as
Definition 3.
Let and . If inequality
is fulfilled and , where , , then function Φ is called -convex modified of the second type on I and this set of functions will be denoted as
Throughout the paper, for -convex modified functions of the first or, of the second type, we assume that and .
The following results are extended versions of Jensen–Mercer inequality (3).
Theorem 1.
Let be an integrable and -convex function. Then, the following Mercer’s type inequality holds:
for , and , such that .
Proof.
Putting and , we have . Now, using the -convexity of , we have
By adding the corresponding sides of the inequalities, we obtain
From the above, the desired inequality (8) is easily obtained. □
Corollary 1.
Remark 1.
For , Corollary 1 leads to a correct version of Lemma 3.1 of [11].
Theorem 2.
Let be an integrable and . Then, the following Mercer’s-type inequality holds:
for , and such that .
Proof.
The proof is analogous to that of Theorem 1. Taking , and combining inequalities
results in inequality (10). □
Corollary 2.
Theorem 3.
Let be an integrable and . Then, the following Mercer’s type inequality holds:
for , and , such that .
Proof.
The proof is analogous to that of Theorem 1. Taking , and combining inequalities
yields inequality (11). □
Corollary 3.
Let be an integrable and . Then, from Theorem 3, we have
for , and
Remark 2.
For and , we have , moreover, Theorems 2 and 3 (or, Corollaries 2 and 3) become the Jensen–Mercer inequality for convex functions (3).
Remark 3.
Other variants of the Jensen–Mercer inequality (2), for different notions of convexity, can be found in [16,22,23,24,25].
In the remainder of this paper, we aim to give generalizations of Hermite–Hadamard inequality (4) via non-conformable fractional integrals defined by Nápoles et al. in [26].
Definition 4.
Let and . For each function , we define
for every
Definition 5.
Let and . For each function , that is the linear space
let us define the fractional integrals
for every . Here, for we have .
Definition 6.
More details on the fractional integral and the corresponding fractional derivative can be read in [26].
Fractional differential and integral computations have been widely used in many fields of applied sciences. The interested reader can read about the role of fractional calculus in the study of biological models and chemical processes in [27,28,29].
2. Inequalities for Convex Functions
In this section, we obtain analogues of Hermite–Hadamard inequality (4) for non-conformable fractional operators (13) using Jensen–Mercer inequalities.
Remark 4.
If in (2), we take and , then we have
Theorem 4.
Let . If and Φ is convex on , then
where and .
Proof.
If in (14), we choose and , and multiply by , then we can write the inequality
Now, by integrating the resulting inequality with respect to on and changing the variable, we obtain
After dividing both sides of the last inequality by , we get the left inequality in (15).
For the proof of the second inequality of (15), keeping in mind that is convex, one can write
By multiplying both sides of last inequality by and by integrating with respect to t on and changing the variables, we obtain
By multiplying the last inequality by and adding to both sides, we get the right-hand side of (15):
Thus, inequality (15) is proved. □
Corollary 4.
For under the assumptions of Theorem 4, we get
for all . This inequality was obtained by Kian and Moslehian in ([30], Theorem 2.1), and by Ögülmüs and Sarikaya in ([17], Remark 2.2).
Theorem 5.
Let . If and is convex on , then we have
where and
Proof.
To prove inequality (16), we use the left-hand side of (14) and choose , to obtain the auxiliary inequality
More precisely, we use the equivalent inequality
Multiplying both sides of (17) by , integrating with respect to t on and changing the variables yields
It is easy to see that left-hand side of (16) is proved. To prove the remaining part of (16), we need the following inequalities:
and
By summing the above inequalities, we have
By multiplying both sides (17) by , integrating with respect to t on and changing the variables, we obtain
Corollary 5.
For , under the assumptions of Theorem 5, we have
for all . This inequality was obtained by Kian and Moslehian in ([30], Theorem 2.1), and by Ögülmüs and Sarikaya in ([17], Remark 2.2).
3. Inequalities for General Convex Functions
By considering -convexity modified in the first and the second sense, we give analogues of Hermite–Hadamard inequality (4) for fractional operators (13) using Jensen–Mercer inequalities proven for these classes. Before that, we recall the following identity obtained by Nápoles et al. in [26] (see Lemma 1).
Lemma 1.
Let be a differentiable function. If , then we have
where and
If in Lemma 1, we substitute in place of and in place of , we get the next equation.
Corollary 6.
Under the assumptions of Lemma 1, we have
where , and
Theorem 6.
Let be a differentiable function. If and , then the following inequality holds for all , :
where is from Corollary 2.
Proof.
From Corollary 6 and modulus properties, we can write
Using -convexity of the first sense of function and Corollary 2, for integral , we get
One can write for the second integral similarly
Thus, we have
Corollary 7.
If in Theorem 6, we choose and , then we have
If, in addition, , then
Theorem 7.
Let be a differentiable function. If and , then the following inequality holds for all , :
where is from Corollary 3.
Proof.
The proof is analogous to that of Theorem 7, but with the use of Corollary 3 instead of Corollary 2. □
Corollary 8.
If in Theorem 7, we choose , and , then we have
Theorem 8.
Let be a differentiable function. If and , then for all , , with , the following inequality holds:
where
Proof.
From Lemma 6 and modulus properties, we can write (21). Using the well-known Hölder integral inequality and Corollary 2, since , we get
Since
we can write similarly for the second integral
Corollary 9.
If in Theorem 8, we choose , and , then we have
Theorem 9.
Let be a differentiable function. If and , then for all , , with , the following inequality holds:
where
Proof.
The proof is analogous to that of Theorem 8, but with the use of Corollary 3 instead of Corollary 2. □
Corollary 10.
If in Theorem 9, we choose , and , then we have
Theorem 10.
Let be a differentiable function. If and , then for all , , , we have
where
Proof.
We first write (21). Then, using the well-known power–mean integral inequality and Corollary 2, since , for the integral , we obtain
One can write for the second integral similarly
Corollary 11.
If in Theorem 10, we choose , and , then we have
If, in addition, we suppose , then we get (22).
Theorem 11.
Let be a differentiable function. If and , then for all , , , we have
where
Proof.
The proof is analogous to that of Theorem 10, but with the use of Corollary 3 instead of Corollary 2. □
Corollary 12.
If in Theorem 11, we choose , and , then we have
If, in addition, we suppose , then we get (23).
4. Applications
Throughout the paper, we examined the fractional integral sums
for .
We demonstrate the scope and strength of our results through three examples, two related to trigonometric functions and one to arithmetic means.
First, consider a convex function. Let , , which is convex on , and fix . Then, according to Theorem 4, we have the inequality
for all .
Second, we consider a non-convex function that has a convex derivative in absolute value. Let , , which has a convex derivative on , and fix . Keeping Remark 2 in mind, applying Corollary 7 or Corollary 8 (with x in place of and y in place of ) yields
for all .
Finally, consider the convex function , with , and fix . Then, according to Theorem 4, we have
for , from which we obtain an inequality of arithmetic means:
where denotes the arithmetic mean .
5. Conclusions
In the present work, we obtained interesting results pertaining to the Jensen–Mercer-type Hermite–Hadamard inequalities via non-conformable integrals, using the classical convex, -convex, and -convex modified functions. Thus, we presented various relevant fractional inequalities related to convex functions and differentiable functions of general convex derivative in absolute value.
As applications, we gave examples of functions for which our main inequalities can be applied, and we presented the resulting inequalities.
Our results are expected to provide motivation to generate further research on inequalities that includes other notions of convexity, such as new variants of the Hermite–Hadamard–Mercer inequalities obtained in this work. For example, instead of working with the operators of [26], one can consider the following more general fractional integral:
Definition 7
([31]). Let , such that Generalized fractional Riemann–Liouville integral of order and , , is given as follows:
with , and . Obviously .
By considering the kernel , we have
and we get the –Riemann–Liouville fractional integral in Definition 2.1 of [32]. Furthermore, by setting , we obtain the Katugampola fractional integral (see [33]).
Author Contributions
Writing—original draft preparation, B.B., P.K. and J.E.N.V. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Butt, S.I.; Agarwal, P.; Yousaf, S.; Guirao, J.L.G. Generalized fractal Jensen and Jensen–Mercer inequalities for harmonic convex function with applications. J. Inequal. Appl. 2022, 2022, 1. [Google Scholar] [CrossRef]
- Deng, Y.; Ullah, H.; Khan, M.A.; Iqbal, S.; Wu, S. Refinements of Jensen’s Inequality via Majorization Results with Applications in the Information Theory. J. Math. 2021, 2021, 1951799. [Google Scholar] [CrossRef]
- Dragomir, S.S. Some reverses of the Jensen inequality with applications. Bull. Aust. Math. Soc. 2013, 87, 177–194. [Google Scholar] [CrossRef]
- Duc, D.T.; Hue, N.N. Jensen-type inequalities and their applications. J. Math. Inequal. 2020, 14, 319–327. [Google Scholar] [CrossRef]
- Lu, G. New refinements of Jensen’s inequality and entropy upper bounds. J. Math. Inequal. 2018, 12, 403–421. [Google Scholar] [CrossRef]
- Varosanec, S. On h-convexity. J. Math. Anal. Appl. 2007, 326, 303–311. [Google Scholar] [CrossRef]
- Mitrinovic, D.S.; Pecaric, J.E.; Fink, A.M. Classical and New Inequalities in Analysis; Springer Science+Business Media: Dordrecht, The Netherlands, 1993. [Google Scholar] [CrossRef]
- Mercer, A.M. A variant of Jensen’s inequality. J. Inequal. Pure Appl. Math. 2003, 4, 73. [Google Scholar]
- Khan, A.R.; Pecaric, J.; Praljak, M. A Note on Generalized Mercer’s Inequality. Bull. Malays. Math. Sci. Soc. 2017, 40, 881–889. [Google Scholar] [CrossRef]
- Moradi, H.R.; Furuichi, S. Improvement and generalization of some Jensen-Mercer-type inequalities. J. Math. Inequal. 2020, 14, 377–383. [Google Scholar] [CrossRef]
- Vivas Cortez, M.J.; Hernández Hernández, J.E. Una Variante de la desigualdad de Jensen-Mercer para funciones h–convexas y funciones de operadores h–convexas. Revista MATUA 2017, 4, 62–76. [Google Scholar]
- Dragomir, S.S.; Pearce, C. Selected Topics on Hermite-Hadamard Inequalities and Applications, Science Direct Working Paper No S1574-0358(04)70845-X. Available online: https://ssrn.com/abstract=3158351 (accessed on 24 May 2023).
- Abdeljawad, T.; Ali, M.A.; Mohammed, P.O.; Kashuri, A. On inequalities of Hermite-Hadamard-Mercer type involving Riemann-Liouville fractional integrals. AIMS Math. 2021, 6, 712–725. [Google Scholar] [CrossRef]
- Aljaaidi, T.A.; Pachpatte, D.B. The Hermite–Hadamard–Mercer Type Inequalities via Generalized Proportional Fractional Integral Concerning Another Function. Int. J. Math. Math. Sci. 2022, 2022, 6716830. [Google Scholar] [CrossRef]
- Butt, S.I.; Yousaf, S.; Asghar, A.; Khan, K.A.; Moradi, H.R. New Fractional Hermite–Hadamard–Mercer Inequalities for Harmonically Convex Function. J. Funct. Spaces 2021, 2021, 5868326. [Google Scholar] [CrossRef]
- Iscan, I. Jensen–Mercer inequality for GA-convex functions and some related inequalities. J. Inequal. Appl. 2020, 2020, 212. [Google Scholar] [CrossRef]
- Ögülmüs, H.; Sarikaya, M.Z. Hermite-Hadamard-Mercer Type Inequalities for Fractional Integrals. Filomat 2021, 35, 2425–2436. [Google Scholar] [CrossRef]
- Zhao, J.; Butt, S.I.; Nasir, J.; Wang, Z.; Tlili, I. Hermite–Jensen–Mercer Type Inequalities for Caputo Fractional Derivatives. J. Funct. Spaces 2020, 2020, 7061549. [Google Scholar] [CrossRef]
- Nápoles Valdés, J.E.; Rabossi, F.; Samaniego, A.D. Convex functions: Ariadne’s thread or Charlotte’s Spiderweb? Adv. Math. Model. Appl. 2020, 5, 176–191. [Google Scholar]
- Bayraktar, B.; Nápoles, J.E. Hermite–Hadamard weighted integral inequalities for (h,m)-convex modified functions. Fract. Differ. Calc. 2022, 12, 235–248. [Google Scholar] [CrossRef]
- Bayraktar, B.; Nápoles, J.E. New generalized integral inequalities via (h,m)-convex modified functions. Izv. Inst. Mat. Inform. 2022, 60, 3–15. [Google Scholar] [CrossRef]
- Alomari, M.W. Mercer’s inequality for h-convex functions. Turkish J. Ineq. 2018, 2, 38–41. [Google Scholar]
- Butt, S.I.; Nasir, J.; Qaisar, S.; Abualnaja, K.M. k-Fractional Variants of Hermite-Mercer-Type Inequalities via s-Convexity with Applications. J. Funct. Spaces 2021, 2021, 5566360. [Google Scholar] [CrossRef]
- Khan, M.A.; Khan, A.R.; Pecaric, J. On the refinements of Jensen-Mercer’s inequality. Rev. Anal. Numér. Théor. Approx. 2012, 41, 62–81. [Google Scholar] [CrossRef]
- Niezgoda, M. A generalization of Mercer’s result on convex functions. Nonlinear Anal. 2009, 71, 2771–2779. [Google Scholar] [CrossRef]
- Nápoles Valdés, J.E.; Rodriguez, J.M.; Sigarreta, J.M. New Hermite–Hadamard Type Inequalities Involving Non-Conformable Integral Operators. Symmetry 2019, 11, 1108. [Google Scholar] [CrossRef]
- Akgül, A.; Khoshnaw, S.H.A. Application of fractional derivative on non-linear biochemical reaction models. Int. J. Intell. Netw. 2020, 1, 52–58. [Google Scholar] [CrossRef]
- Rezapour, S.; Deressa, C.T.; Hussain, A.; Etemad, S.; George, R.; Ahmad, B. A Theoretical Analysis of a Fractional Multi-Dimensional System of Boundary Value Problems on the Methylpropane Graph via Fixed Point Technique. Mathematics 2022, 10, 568. [Google Scholar] [CrossRef]
- Sintunavarat, W.; Turab, A. A unified fixed point approach to study the existence of solutions for a class of fractional boundary value problems arising in a chemical graph theory. PLoS ONE 2022, 17, e0270148. [Google Scholar] [CrossRef]
- Kian, M.; Moslehian, M.S. Refinements of the operator Jensen–Mercer inequality. Electron. J. Linear Algebra 2013, 26, 742–753. [Google Scholar] [CrossRef]
- Bayraktar, B.; Nápoles Valdes, J.E. Generalized Fractional Integral Inequalities for (h,m,s)-convex modified functions of second type. Sahand Commun. Math. Anal. 2023; submitted. [Google Scholar]
- Sarikaya, M.Z.; Dahmani, Z.; Kiris, M.E.; Ahmad, F. (k,s)-Riemann-Liouville fractional integral and applications. Hacet. J. Math. Stat. 2016, 45, 77–89. [Google Scholar] [CrossRef]
- Katugampola, U.N. New approach to a generalized fractional integral. Appl. Math. Comput. 2011, 218, 860–865. [Google Scholar] [CrossRef]
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