1. Introduction
The idea of convex analysis has a strong background and has been the inspiration for excellent research for more than a century in the field of mathematics. Various augmentations, variations, and speculations of the theory of convexity have been taken into consideration by numerous researchers. This theory develops and provides numerical procedures to handle and study complex problems in the field of mathematics. This theory has been very inspirational and popular among mathematicians as it possesses a wide range of potential applications in pure and applied sciences.
The idea of inequalities is perhaps one of the most important elements of science having various applications in different branches of mathematics, engineering, and physics. Currently, the theory of inequalities is still intensively developed. In this regard, the Hermite-Hadamard type inequality is broadly notable and has been read and generalized for various sorts of convex functions under different parameters and conditions. In recent times, the correlation between convexity and inequalities has acquired a great deal of consideration among mathematicians because of their basic definitions and properties. Numerous mathematicians and researchers are working in the direction of this inequality for estimating the fractional version of the Hermite-Hadamard inequality utilizing various types of convexity (see, for example, refs. [
1,
2,
3,
4,
5,
6,
7,
8,
9,
10]).
The theory of fractional differential equations was initiated in the 19th century by Riemann and Liouville, who introduced the preliminary concepts of the theory. Since then, many new versions of these definitions, such as Gruenwald-Letnikov derivatives, Caputo derivatives, and their multidimensional analogs, have appeared in the literature. This hypothesis moreover has been accepted as a critical part in the progression of the idea of inequalities. In research activities, the theory of inequalities has an extraordinary arrangement of employment in financial issues, numerical analysis, probability theory, and many more. Fractional differentiable inequalities have applications in fractional differential equations, the most important ones being to establish the uniqueness of the solution of initial-value problems and give upper bounds to their solution. These applications have motivated many researchers in the field of integral inequalities to investigate a few extensions and generalizations using different fractional differential and integral operators. For some related articles, the readers can see [
11,
12,
13,
14,
15,
16].
One of the main objectives of this article is to present a new fractional version of the Hermite-Hadamard inequality, where Minkowski and Hölder’s inequality is used to prove the right-hand side of the inequality. We derive general Hermite-Hadamard-type inequalities for functions whose second derivatives are h-convex by using the k-fractional operator. Next, some new integral identities are studied and employing these and with the help of some well-known fundamental inequalities, such as the Hölder, Hölder-İscan, power-mean inequality, we establish some refinements of the Hermite-Hadamard-type inequality for twice-differentiable mappings. Moreover, some interesting applications related to -digamma functions are discussed.
2. Preliminaries and Basic Concept
The main objective of this section is to recall some known definitions and concepts.
Definition 1 ([
17]).
A real-valued function is known as convex on the interval , if:holds for all and . Theorem 1 ([
18]).
Let be a convex function with and Then, the Hermite-Hadamard inequality is expressed as follows: In the recent past, the classical Hermite-Hadamard inequality (
1) was generalized and extended extensively by numerous mathematicians under the assumption of some interesting new definitions as a generalization of the convex function.
In the year 2007, Varošanec [
19] introduced and investigated the term
-convexity.
Definition 2 ([
19]).
Let be a positive function, then a non-negative function is an “-convex function” if , , we have: Definition 3 ([
20]).
Let , then an inequality of the form:is said to be a super-additive function. In the field of fractional calculus, several mathematicians worked on the concept of
-convexity and presented different types of Hermite-Hadamard type inequalities. For the readers, see [
21,
22,
23,
24,
25,
26,
27,
28,
29,
30,
31,
32,
33,
34,
35,
36] and the references cited therein.
Definition 4 ([
11]).
Let . The fractional integrals and of order are defined by:respectively. In [
11], Sarikaya et al. proved the following Hadamard-type inequalities for Riemann-Liouville fractional integrals as follows:
Theorem 2 ([
11]).
Let be a positive mapping with , and be fractional operator. Then, the following inequality for fractional integral holds if ℘ is a convex function. Definition 5 ([
25]).
Let and , then k-fractional integrals and of order are defined by:respectively, where Theorem 3 ([
25]).
Let k > 0, be a positive mapping with , and be fractional operator. Then, the following inequality for fractional integral holds if ℘ is a convex function. Lemma 1 ([
25]).
Let be a differentiable mapping on , where with . If , then the following equality for the fractional integral holds: For some recent generalization of Hermite-Hadamard type inequalities via fractional operators, readers can refer to [
26,
27,
28,
29,
30] and the references cited therein. Recently, in [
27,
28], the authors introduced a new class of convex functions and presented the Hermite-Hadamard inequality using a generalized Riemann-Liouville fractional integral operator concerning a monotonic function. Cortez et al. in [
29] presented some trapezium-type inequalities for generalized coordinated convex function via a new form of the Riemann-Liouville fractional operator using Raina’s special function. Kashuri et al. [
30,
31] worked on the k-Riemann-Liouville fractional operator to study the inequalities of Hermite-Hadamard type. Farid et al. in [
32,
33] extended their work on k-fractional inequalities for quasi-convexity and exponential convexity. Interested readers can also refer to the references cited in the above-mentioned articles to obtain detailed knowledge about generalized fractional operators and inequalities.
Motivated by the above results, the article is structured as follows: In
Section 3, a new version of the Hermite-Hadamard inequality by using the concept of the
-convex function is presented. In
Section 4, refinements of the Hermite-Hadamard type inequality for twice-differentiable functions are discussed.
Section 5 deals with the application of
q-digamma functions and related results. In the end, a conclusion is given in
Section 6.
3. Hermite-Hadamard Inequality via Fractional Operator
The main focus of this section is to investigate and prove the Hermite-Hadamard inequality via the fractional operator, namely the k-fractional operator.
Theorem 4. Let a function be -convex with . If , then the following inequality for the fractional integral holds:where Proof. Employing the definition of
-convexity, we have:
and:
Adding these inequalities, one has:
Substituting
and
and multiplying (
4) by
, then integrating the result over
, we then obtain:
which simplifies to:
Hence, the proof of the first part of the theorem is complete.
For the second part of Theorem 4, we use Hölder’s inequality and then Minkowski’s inequality for the RHS of (
5):
This completes the proof. □
If we put in Theorem 4, we obtain a new inequality for convex functions.
Corollary 1. Let be a convex function with . If , then the following inequality for the fractional integral holds:where Remark 1. If we use , in Corollary 1, then the following inequality is obtained:where Remark 2. If we use , in Corollary 1, then the following inequality is obtained:where If we put in Theorem 4, then we obtain the following inequality for s-convex functions.
Corollary 2. Let be a s-convex function with . If , then the following inequality for the fractional integral holds:where Corollary 3. If we put in Theorem 4, then the following inequality holds:where 4. Main Results
Lemma 2. Let be a differentiable mapping with , , and , be right and left fractional operators. If , then the following equality holds: Proof. Using (
11) and (
12) in (
10), the proof of the desired lemma is complete. □
Before establishing our main results, we need the following lemmas.
Lemma 3. Let be a differentiable mapping on , where with . If , then the following equality for the fractional integral holds: Proof. To investigate the require equality, we apply the result by Wu et al. [
25]:
It is enough to verify that:
Consequently, integration by parts gives,
Now, using the fact:
we attain the required equality, and the proof is complete. □
Remark 3. If we put in Lemma 3, then [[36], Lemma 2.1, page-2243], is recovered. Remark 4. If we put in Lemma 3, then [[37], Lemma 1, page 1066], is recovered. Lemma 4. Let be a differentiable mapping with , , and be right and left fractional operators. If , then the following equality holds: Proof. The proof can made in a similar manner as that of Lemma 3 and using the result of Lemma 2. □
Theorem 5. Let be a differentiable function on , where with and . If is an -convex function, then the following fractional integral inequality holds: Proof. Using Lemma 4 and employing the
-convexity of
, we attain:
□
Corollary 4. Choosing in Theorem 5, then the following inequality for the convex function is obtained: Remark 5. For an m-convex function, we obtain a new result from Theorem 5. Corollary 5. Choosing in Theorem 5, then the following inequality for the s-convex function is obtained: Corollary 6. Choosing in Theorem 5, then the following inequality for the -convex function is obtained: Corollary 7. Choosing in Theorem 5, then the following inequality for the P-function is obtained: Theorem 6. Let be a twice-differentiable function on , where with and . If is an -convex function, then: Proof. Employing Lemma 4, Hölder’s inequality, and the
-convexity of
, we have:
□
Corollary 8. Choosing in Theorem 6, then the following inequality for the convex function is obtained: Corollary 9. Choosing in Theorem 6, then the following inequality for the s-convex function is obtained: Corollary 10. Choosing in Theorem 6, then the following inequality for the exponential-type convex function is obtained: Corollary 11. Choosing in Theorem 6, then the following inequality for the -convex function is obtained: Theorem 7. Let be a differentiable function on , where with and . If is an -convex function, then we have: Proof. Employing Lemma 4, Hölder’s inequality, and the
-convexity of
, we have:
□
Corollary 12. Choosing in Theorem 7, then the following inequality for the convex function is obtained: Corollary 13. Choosing in Theorem 7, then the following inequality for the s-convexity is obtained: Theorem 8. Let be a differentiable function on , where with and . If is an -convex function, then: Proof. Employing Lemma 4, the power-mean inequality, and the
-convexity of
,
□
Corollary 14. Choosing in Theorem 8, then the following inequality for the convex function is obtained: Corollary 15. Choosing in Theorem 8, then the following new inequality for the s-convexity is obtained: Theorem 9. Let be a differentiable function on , where with and . If is an -convex function, then: Proof. Employing Lemma 4, the Hölder-Íscan integral inequality, and the
-convexity of
, we have:
□
Corollary 16. Choosing in Theorem 9, then the following inequality for the convex function is obtained: Corollary 17. Choosing in Theorem 9, then the following inequality for the exponential-type convexity is obtained: Corollary 18. Choosing in Theorem 9, then the following inequality for the s-convexity isobtained: 5. Applications to Special Functions
Jolevska-Tuneska et al. [
38] summed up the digamma function for non-negative integers. Further, the polygamma function was generalized for negative integers by Salem and Kilicman [
39]. Salem in his articles [
40,
41] elaborated the idea of the neutrix and neutrix limit and also defined the
-gamma, the incomplete gamma functions, and their derivatives for negative values of
x. Later, Krattenthaler and Srivastava [
42] investigated the concept of the
-digamma function
. They expressed that
tends to the digamma function
, if
. Salem [
43] again studied some fundamental properties and generalizations of
-digamma functions.
For any complex number a, we define
The -analogue of the gamma function is:
...
The -integral representation is given as:
-digamma function: Suppose
; the
-digamma(psi) function
is the
-analogue of the Psi or digamma function
defined by:
For
and
the
-digamma function
is defined by:
In [
42], it was proven that
.
We also use the fact that,
Proposition 1. For and , then as a result, we have: Proof. Setting
, we have that
is a completely monotone function on
for each
. Now, using Corollary 4, we acquire Inequality (
13). □
Proposition 2. For and , then as a result, we have: Proof. The proof is completed in a similar fashion as that of Proposition 1 and applying Corollary 7. □
Proposition 3. For and , then as a result, we have: Proof. The proof is completed in a similar fashion as that of Proposition 1 and applying Corollary 8. □
Proposition 4. For and , then as a result, we have: Proof. The proof is completed in a similar fashion as that of Proposition 1 and applying Corollary 11. □
Proposition 5. For and , then as a result, we have: Proof. The proof is completed in a similar fashion as that of Proposition 1 and applying Corollary 14. □
Proposition 6. For and , then as a result, we have: Proof. The proof is completed in a similar fashion as that of Proposition 1 and applying Corollary 16. □
6. Conclusions
In this article, we presented a new fractional version of the Hermite-Hadamard type inequality using the Hölder and the Minkowski inequality. Next, we established new integral identities for differentiable mappings, and employing these identities, we proved our main results. Some special cases for different types of convexities were derived as well. Additionally, some applications of our presented results were investigated through -digamma functions. The techniques and ideas employed in this article can be generalized on the coordinates, quantum calculus, interval analysis, and preinvexity.
Author Contributions
Conceptualization, S.K.S.; M.T. and H.A.; methodology, S.K.S. and M.T.; software, S.K.S.; M.T. and H.A.; validation, S.K.S.; M.T. and H.A.; formal analysis, A.A.A.; B.F.F. and P.T.; investigation, S.K.S. and M.T.; resources, H.A.; A.A.A.; B.F.F. and P.T.; data curation, S.K.S.; M.T. and H.A.; writing—original draft preparation, S.K.S. and M.T.; writing—review and editing, S.K.S.; M.T. and H.A.; supervision, H.A.; A.A.A.; B.F.F. and P.T.; project administration, S.K.S.; M.T. and H.A.; funding acquisition, A.A.A.; B.F.F. and P.T. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by Taif University Researchers Supporting Project number (TURSP-2020/260), Taif University, Taif, Saudi Arabia.
Acknowledgments
We would like to thank Taif University Researchers Supporting Project number (TURSP-2020/260), Taif University, Taif, Saudi Arabia.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Xi, B.Y.; Qi, F. Some integral inequalities of Hermite-Hadamard type for convex functions with applications to means. J. Funct. Spaces. Appl. 2012, 2012, 980438. [Google Scholar] [CrossRef] [Green Version]
- Özcan, S.; İşcan, İ. Some new Hermite-Hadamard type integral inequalities for the s-convex functions and theirs applications. J. Inequal. Appl. 2019, 2019, 201. [Google Scholar] [CrossRef] [Green Version]
- Hudzik, H.; Maligranda, L. Some remarks on s-convex functions. Aequ. Math. 1994, 48, 100–111. [Google Scholar] [CrossRef]
- Kadakal, M.; İşcan, İ. Exponential type convexity and some related inequalities. J. Inequal. Appl. 2020, 2020, 82. [Google Scholar] [CrossRef]
- Butt, S.I.; Tariq, M.; Aslam, A.; Ahmad, H.; Nofel, T.A. Hermite-Hadamard type inequalities via generalized harmonic exponential convexity. J. Funct. Spaces 2021, 2021, 5533491. [Google Scholar] [CrossRef]
- Butt, S.I.; Kashuri, A.; Tariq, M.; Nasir, J.; Aslam, A.; Geo, W. Hermite-Hadamard type inequalities via n-polynomial exponential type convexity and their applications. Adv. Differ. Equ. 2020, 2020, 508. [Google Scholar] [CrossRef]
- Butt, S.I.; Kashuri, A.; Tariq, M.; Nasir, J.; Aslam, A.; Geo, W. n–polynomial exponential type p-convex function with some related inequalities and their applications. Heliyon 2020, 6, e05420. [Google Scholar] [CrossRef]
- Tariq, M.; Ahmad, H.; Sahoo, S.K. The Hermite–Hadamard type inequality and its estimations via generalized convex functions of Raina type. Math. Model. Numer. Simul. Appl. 2021, 1, 32–43. [Google Scholar] [CrossRef]
- Latif, M.A. New Hermite-Hadamard type integral inequalities for GA-convex functions with applications. Analysis 2014, 34, 379–389. [Google Scholar] [CrossRef]
- Tariq, M.; Nasir, J.; Sahoo, S.K.; Mallah, A.A. A note on some Ostrowski type inequalities via generalized exponentially convex function. J. Math. Anal. Model. 2021, 2, 1–15. [Google Scholar]
- Sarikaya, M.Z.; Set, E.; Yaldiz, H.; Basak, N. Hermite-Hadamard’s inequalities for fractional integrals and related fractional inequalities. Math. Comput. Mod. 2013, 57, 2403–2407. [Google Scholar] [CrossRef]
- Chen, H.; Katugampola, U.N. Hermite-Hadamard and Hermite-Hadamard-Fejr type inequalities for generalized fractional integrals. J. Math. Anal. Appl. 2017, 446, 1274–1291. [Google Scholar] [CrossRef] [Green Version]
- Han, J.; Mohammed, P.O.; Zeng, H. Generalized fractional integral inequalities of Hermite-Hadamard type for a convex function. Open Math. 2020, 18, 794–806. [Google Scholar] [CrossRef]
- Awan, M.U.; Talib, S.; Chu, Y.M.; Noor, M.A.; Noor, K.I. Some new refinements of Hermite-Hadamard type inequalities involving Riemann-Liouville fractional integrals and applications. Math. Prob. Eng. 2020, 2020, 3051920. [Google Scholar] [CrossRef] [Green Version]
- Aljaaidi, T.A.; Pachpatte, D.B. The Minkowski’s inequalities via ψ-Riemann-Liouville fractional integral operators. Rendiconti del Circolo Mat. 2020, 17, 1–4. [Google Scholar] [CrossRef]
- Mohammed, P.O.; Abdeljawad, T.; Jarad, F.; Chu, Y.M. Existence and uniqueness of uncertain fractional backward difference equations of Riemann-Liouville type. Math. Prob. Eng. 2020, 2020, 6598682. [Google Scholar] [CrossRef]
- Niculescu, C.P.; Persson, L.E. Convex Functions and Their Applications; Springer: New York, NY, USA, 2006. [Google Scholar]
- Hadamard, J. Étude sur les propriétés des fonctions entiéres en particulier d’une fonction considéréé par Riemann. J. Math. Pures Appl. 1893, 58, 171–215. [Google Scholar]
- Varošanec, S. On h-convexity. J. Math. Anal. Appl. 2007, 326, 303–311. [Google Scholar] [CrossRef] [Green Version]
- Alzer, H. A superadditive property of Hadamard’s gamma function. Abh. Math. Semin. Univ. Hambg. 2009, 79, 11–23. [Google Scholar] [CrossRef]
- Wu, Y. On inequalities for s-convex function based on Katugampola fractional integral. J. Phys. Conf. Ser. 2020, 1575, 012012. [Google Scholar] [CrossRef]
- Kermausuo, S.; Nwaeze, E.R. New integral inequalities of Hermite-Hadamard type via the Katugampola fractional integrals for strongly η-quasiconvex functions. J. Anal. 2020, 29, 633–647. [Google Scholar] [CrossRef]
- Sarikaya, M.Z.; Ertugral, F. On the generalized Hermite-Hadamard inequalities. Ann. Univ. Craiova Math. Comput. Sci. Ser. 2020, 15, 193–213. [Google Scholar]
- Nale, A.B.; Panchal, S.K.; Chinchane, V.L. Certain fractional integral inequalities using generalized Katugampola fractional integral operator. Malaya J. Mat. 2020, 8, 809–814. [Google Scholar]
- Wu, S.; Iqbal, S.; Aamir, M.; Samraiz, M.; Younus, A. On some Hermite-Hadamard inequalities involving k-fractional operators. J. Inequal. Appl. 2021, 2021, 32. [Google Scholar] [CrossRef]
- Simić, S.; Bin-Mohsin, B. Simpson’s rule and Hermite-Hadamard inequality for non-convex functions. Mathematics 2020, 8, 1248. [Google Scholar] [CrossRef]
- Mohammed, P.O.; Abdeljawad, T.; Zeng, S.; Kashuri, A. Fractional Hermite-Hadamard integral inequalities for a new class of convex functions. Symmetry 2020, 12, 1485. [Google Scholar] [CrossRef]
- Mohammed, P.O.; Abdeljawad, T.; Kashuri, A. Fractional Hermite-Hadamard-Fejer inequalities for a convex function with respect to an increasing function involving a positive weighted symmetric function. Symmetry 2020, 12, 1503. [Google Scholar] [CrossRef]
- Vivas-Cortez, M.; Kashuri, A.; Liko, R.; Hernández, J.E.H. Trapezium-type inequalities for an extension of Riemann-Liouville Fractional integrals using Raina’s special function and generalized coordinate convex functions. Axioms 2020, 9, 117. [Google Scholar] [CrossRef]
- Kashuri, A.; Liko, R. Hermite–Hadamard type integral inequalities involving k–Riemann–Liouville fractional integrals and their applications. Int. J. Math. Comput. Sci. 2021, 15, 18–23. [Google Scholar]
- Kashuri, A.; Liko, R. Hermite-Hadamard type inequalities for generalized (s,m,ϕ)-preinvex functions via k-fractional integrals. Tbil. Math. J. 2017, 10, 73–82. [Google Scholar]
- Farid, G.; Jung, C.Y.; Ullah, S.; Nazeer, W.; Waseem, M.; Kang, S.M. Some generalized k-fractional integral inequalities for quasi-convex functions. J. Comp. Anal. Appl. 2021, 29, 454–467. [Google Scholar]
- Rehman, A.U.; Farid, G.; Bibi, S.; Jung, C.Y.; Kang, S.M. k-fractional integral inequalities of Hadamard-type for exponentially (s,m)-convex functions. AIMS Math. 2021, 6, 882–892. [Google Scholar] [CrossRef]
- Set, E.; Butt, S.I.; Akdemir, A.O.; Karaoǧlan, A.; Abdeljawad, T. New integral inequalities for differentiable convex functions via Atangana-Baleanu fractional integral operators. Chaos Solitons Fractals 2021, 143, 110554. [Google Scholar] [CrossRef]
- Set, E.; Gzpinar, A.; Butt, S.I. A study on Hermite-Hadamard type inequalities via new fractional conformable integrals. Asian-Eur. J. Math. 2021, 14, 2150016. [Google Scholar] [CrossRef]
- Wang, J.R.; Li, X.; Fečkan, M.; Zhou., F. Hermite–Hadamard-type inequalities for Riemann–Liouville fractional integrals via two kinds of convexity. Appl. Anal. 2013, 92, 2241–2253. [Google Scholar] [CrossRef]
- Özdemir, M.E.; Avcı, M.; Set, E. On some inequalities of Hermite–Hadamard-type via m-convexity. Appl. Math. Lett. 2010, 23, 1065–1070. [Google Scholar] [CrossRef] [Green Version]
- Jolevska-Tuneska, B.; Jolevski, I. Some results on the digamma function. Appl. Math. Inform. Sci. 2013, 7, 167–170. [Google Scholar] [CrossRef]
- Salem, A.; Kilicman, A. Estimating the polygamma functions for negative integers. J. Ineq. Appl. 2013, 2013, 523. [Google Scholar] [CrossRef] [Green Version]
- Salem, A. The neutrix limit of the q-Gamma function and its derivatives. Appl. Math. Lett. 2010, 23, 1262–1268. [Google Scholar] [CrossRef] [Green Version]
- Salem, A. Existence of the neutrix limit of the q-analogue of the incomplete gamma function and its derivatives. Appl. Math. Lett. 2012, 25, 363–368. [Google Scholar] [CrossRef]
- Krattenthaler, C.; Srivastava, H.M. Summations for basic hypergeometric series involving a q-analogue of the digamma function. Comput. Math. Appl. 1996, 32, 73–91. [Google Scholar] [CrossRef] [Green Version]
- Salem, A. Some properties and expansions associated with q-digamma function. Quaest. Math. 2013, 36, 67–77. [Google Scholar] [CrossRef]
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