Abstract
This paper investigates weighted Milne-type () inequalities within the context of Riemann–Liouville () fractional integrals. We establish multiple versions of these inequalities, applicable to different function categories, such as convex functions with differentiability properties, bounded functions, functions satisfying Lipschitz conditions, and those exhibiting bounded variation behavior. In particular, we present integral equalities that are essential to establish the main results, using non-negative weighted functions. The findings contribute to the extension of existing inequalities in the literature and provide a deeper understanding of their applications in fractional calculus. This work highlights the advantage of the established inequalities in extending classical results by accommodating a broader class of functions and yielding sharper bounds. It also explores potential directions for future research inspired by these findings.
Keywords:
weighted integral inequalities; convex analysis; boundedness conditions; Lipschitzian functions; functions of bounded variation MSC:
26D15; 26D10; 26D07
1. Introduction
Numerical integration methods and their associated error bounds have been the subject of extensive research by mathematicians []. When obtaining such estimates for inaccuracies, researchers frequently rely on distinct mathematical estimates, commonly tailored to particular function categories like those exhibiting convexity, boundedness, or Lipschitz continuity [,]. By investigating the properties of such functions, this paper aims to provide more accurate estimates of the error involved when using numerical integration formulas, particularly under the assumption of certain smoothness conditions, such as convexity in the derivatives.
Let us first introduce a numerical integration method and the upper error bounds of it.
The following is the expression for the Milne quadrature formula:
A significant volume of work has addressed fresh upper estimates for the gap between a particular formula and its integral, typically referred to as inequalities. Alomari [] pioneered such results for both bounded functions and functions of bounded variation. In subsequent explorations, numerous researchers investigated these inequalities from different perspectives. For instance, Djenaoui and Meftah [] relied on convexity arguments to establish certain results, while Budak et al. [] adapted them to fractional integrals and examined further function classes, including bounded, Lipschitz, and bounded variations. Benaissa and Sarikaya [] contributed new fractional inequalities for h-convex functions. Meanwhile, other authors [,,,] continued to expand inequalities to various settings, such as fractional integrals with differentiable convex functions, bounded functions, Lipschitz functions, and functions of bounded variation. Desta et al. [] studied inequalities for twice-differentiable functions, and additional contributions covered scenarios involving higher-order differentiable functions [].
Several directions have also aimed at extending inequalities to alternative forms of calculus. Some researchers examined quantum integrals [,,,], while others investigated different fractional integral definitions, such as conformable [,], tempered [,], local fractional [,,], and Katugampola fractional integrals [,], generalized proportional fractional operators [], among others [,,,]. Shehzadi et al. [] introduced inequalities in the framework of coordinated convexity.
The classical fractional integrals are expressed as follows:
Definition 1
([,]). Let . The fractional integrals and are defined by
and
respectively. Here, is assumed to be in , and represents the Gamma function. In the particular case when , the fractional integral coincides with the standard integral.
Definition 2
([]). The hypergeometric function is defined by
with , and is the beta function given by
This work is devoted to broadening the scope of traditional inequalities by incorporating them into the fractional calculus framework through the derivation of innovative weighted estimates based on fractional integrals. Our approach rigorously establishes new error bounds that apply to a range of function families, including those that are convex, bounded, Lipschitz-continuous, and of bounded variation. Central to our analysis is the introduction of a symmetric non-negative weighting function alongside sophisticated integration techniques.
The paper is organized into seven sections. We begin with an introductory discussion and a review of the necessary preliminaries. In Section 2, we present a key integral identity derived using a non-negative weight, which forms the basis for our subsequent results. Section 3 is dedicated to developing weighted inequalities for various function classes within the fractional integral context, with a special focus on differentiable convex functions. Section 4 examines fractional integration results for bounded functions, while Section 5 extends these inequalities to cover Lipschitz functions. In Section 6, we derive weighted fractional estimates for functions exhibiting bounded variation. Finally, Section 7 summarizes our findings on inequalities.
2. Preliminaries and Some Key Identities
In what follows, we suppose that is a non-negative, continuous function, and is symmetric about the midpoint , meaning for all . Based on this, we introduce the functions and by
and
By the symmetry of around the midpoint , the identities below will play a significant role in later developments.
as well as the relations
In particular, for , we obtain
The symmetry of the function is necessary to establish important relations between the left and right fractional integrals. This allows us to derive simplified and symmetric identities such as (2)–(4).
Lemma 1.
Consider a function that is absolutely continuous on the interval , with its derivative being integrable over . Under these conditions, the following identity holds:
where Γ denotes the Gamma function, and
and
Proof.
By applying integration by parts, we easily find
Similarly, for , we obtain
Corollary 1.
Suppose that all conditions stated in Lemma 1 are fulfilled. Then, the following equalities are valid:
and
3. Fractional Weighted Milne-Type Inequalities Under Convexity
This section develops a series of fractional weighted inequalities tailored for convex and differentiable functions. Our strategy is based on bounding the absolute value of a newly formulated integral equality. Additionally, by utilizing classic tools known as Hölder’s and the power-mean inequality, we derive further related results.
Theorem 1.
Suppose the hypotheses of Lemma 1 hold and that the function is convex on . Under these assumptions, we establish the following fractional weighted inequality:
where
Proof.
Starting from the identity (8), we write
Since is convex over , we use the properties of convex functions:
and similarly,
Adding these two inequalities gives
Thus, continuing from (12), we deduce
□
Remark 1.
Taking the function within Theorem 1, the resulting fractional inequality is expressed as follows:
which is proved by Budak and Karagözoğlu in [] (Theorem 2.2).
Proof.
By special choice of for all and by changing variables, we have
This completes the proof. □
Corollary 2.
Taking within Theorem 1, The weighted inequality is obtained as follows:
Remark 2.
In particular, by setting within Corollary 2, we arrive at the classical inequality:
which coincides with the result provided by Budak et al. in [] (Remark 1).
Theorem 2.
Let the conditions outlined in Lemma 1 hold, and assume further that exhibits convexity over the interval for some real number . Under these circumstances, we establish the fractional weighted inequality presented below:
where p and q satisfy .
Proof.
Applying Hölder’s inequality to the estimate in (12), we obtain:
Since is convex on , we can estimate that
Thus, inserting these into the previous inequality, we have
Simplifying the integrals gives
This concludes the proof of Theorem 2. □
Corollary 3.
Taking within Theorem 2, the result reduces to the following inequality:
where denotes the classical hypergeometric function.
Proof.
By selecting throughout the interval and performing an appropriate substitution, we compute
The proof is complete. □
Corollary 4.
By assigning within Theorem 2, we derive the following weighted inequality:
Corollary 5.
If we further specify within Corollary 4, the inequality simplifies as follows:
Theorem 3.
Suppose that the conditions stated in Lemma 1 are satisfied. If the function is convex over for some , then the coming weighted fractional inequality holds:
where the quantity is introduced as in Theorem 1, and we set
Proof.
Starting from inequality (12) and employing the power mean inequality, we derive
Due to the convexity assumption on , the following bounds hold:
Inserting these estimates into the previous inequality gives
thus finalizing the proof. □
4. Fractional Milne-Type Estimates with Weights Involving Functions of Limited Magnitude
This section is devoted to deriving weighted fractional inequalities for functions whose derivatives are bounded.
Theorem 4.
Let the conditions mentioned in Lemma 1 be valid. Suppose further that real constants exist, fulfilling the inequality for every z within . Under these assumptions, we derive the subsequent weighted fractional inequality:
where is given as shown in Theorem 1.
Proof.
Starting from equality (8), we have
Taking the modulus of both sides of (17), it follows that:
Since, by assumption, on , it follows that:
Applying this bound gives
This finishes the proof. □
Remark 3.
If we select within Theorem 4, we derive the coming fractional inequality:
as established by Budak and Karagözoğlu in [] (Theorem 3.1).
Corollary 6.
If we take in Theorem 4, the following weighted inequality is achieved:
Remark 4.
Choosing on in Corollary 6, we retrieve the classical inequality:
as presented by Budak et al. in [] (Corollary 2).
Corollary 7.
Suppose the conditions outlined in Theorem 4 are valid, and consider the existence of a positive real number fulfilling , . Then, we obtain the inequality given below:
Remark 5.
If we additionally set and in Corollary 7, we find
which coincides with the result established by Alomari in [] (Theorem 3.1).
5. Milne-Inspired Fractional Weighted Inequalities for Lipschitz Families
Now, we establish several weighted fractional inequalities for the scenario where functions are Lipschitz continuous.
Theorem 5.
Assume the conditions in Lemma 1 hold, and let be L-Lipschitz function on . Then, the following weighted fractional inequality is valid:
Proof.
The proof is complete. □
Remark 6.
By setting on in Theorem 5, we obtain this fractional inequality:
which corresponds to a result of Budak and Karagözoğlu in [] (Theorem 4.1).
Proof.
Taking on and employing a change of variables, one obtains
This concludes the proof. □
Corollary 8.
Taking in Theorem 5 yields the weighted inequality
Proof.
Observe that
□
Remark 7.
By taking for all in Corollary 8, one obtains the result
which was previously shown by Budak et al. in [] (Corollary 4).
6. Fractionally Weighted Milne-Form Results for Bounded-Variation Functions
In the following, we assume that the function has bounded variation and develop a number of weighted fractional estimates.
Theorem 6.
Suppose has bounded variation on . Then the following weighted fractional inequality holds:
where stands for the total variation of on .
Proof.
Define the function
A straightforward integration by parts argument implies:
It is well known that if has bounded variation on and g is continuous on the same interval, then
From (19), we deduce
Using the integral bound above yields
Remark 8.
If on in Theorem 6, then
matching the conclusion of Budak and Karagözoğlu in [] (Theorem 5.1).
Corollary 9.
Taking in Theorem 6 implies:
Remark 9.
When on and in Corollary 9, one finds
as shown by Alomari in [] (Theorem 2.1).
7. Concluding Remarks
In this work, we introduced several new weighted inequalities for various classes of functions by utilizing Riemann–Liouville fractional integrals. The obtained inequalities are valid for several function classes, including those with differentiable convexity, boundedness, Lipschitz continuity, and bounded variation properties. The integral identities in Section 2 played a fundamental role in developing the presented inequalities. By expanding on existing research, our findings offer new perspectives on the performance of these inequalities across different function categories. Future studies could explore additional extensions of inequalities, particularly those involving other forms of fractional integrals and higher-order differentiability. Moreover, the results may have potential applications in numerical methods, error estimation, and other areas where such inequalities are useful. Such advances are likely to deepen our understanding of fractional calculus and broaden its practical relevance in both mathematics and scientific applications.
Author Contributions
Conceptualization, A.A.A., A.-A.H., H.B. and M.A.B.; Methodology, A.A.A., A.-A.H., H.B. and M.A.B.; Formal analysis, A.A.A., A.-A.H., H.B. and M.A.B.; Investigation, A.A.A., A.-A.H., H.B. and M.A.B.; Writing—original draft, A.A.A., A.-A.H., H.B. and M.A.B.; Writing—review & editing, A.A.A., A.-A.H., H.B. and M.A.B. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by King Khalid University, Grant (RGP.2/163/46) and Princess Nourah bint Abdulrahman University, Grant (PNURSP2025R337).
Data Availability Statement
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.
Acknowledgments
The authors extend their appreciation to the Deanship of Research and Graduate Studies at King Khalid University for funding this work through the Research Groups Program under grant (RGP.2/163/46). The authors would like to acknowledge the Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2025R337).
Conflicts of Interest
The authors declare no conflict of interest.
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