1.
Introduction and preliminaries
The primary contribution to the concept of subadditive functions is due to the work of Hille and Phillips [1]. An extract from Rosenbaum's study on subadditive functions with several variables is also given [2]. The concepts of additivity, subadditivity, and superadditivity are used in many branches of mathematics as well as in mathematical inequalities, see [3,4,5,6,7,8].
Definition 1.1. [9] F:I⊂R→[0,∞) is said to be subadditive function on I, if
holds for all Θ1,Θ2∈I and Θ1+Θ2∈I. If the equality is achieved, then F is said to be additive, otherwise superadditive.
Since many optimization issues require maximizing or minimizing a convex function while taking certain restrictions into account, convex functions are crucial in optimization. Additionally, they have appealing characteristics like a singular global minimum and nearly universal differentiability. Numerous fields, including optimization, game theory, economics, and computer science, use convexity theory. It offers strong tools for understanding and resolving optimization issues, and it has sparked the creation of several algorithms for quickly calculating answers to these issues.
Definition 1.2. [10] F:I⊂R→R is said to be convex, if
holds for all Θ1,Θ2∈I with δ∈[0,1].
The given Hermite-Hadamard inequality (H-H) has a strong connection with convex functions.
Theorem 1.1. [11,12] If F:I⊂R→R is convex on I, then
holds for all Θ1,Θ2∈I and Θ1<Θ2.
There are numerous well-known inequalities that may be obtained using the convexity feature, see [13,14,15,16,17,18].
Let us denote by L[Θ1,Θ2] the set of all Lebesgue integrable functions on [Θ1,Θ2] and by I∘ the interior set of I. The following H-H type for continuous subadditive functions were recently established by Sarikaya and Ali [19].
Theorem 1.2. If F:I⊂R→[0,∞) is a continuous subadditive function with Θ1,Θ2∈I∘ and 0<Θ1<Θ2, then
The fractional calculus focuses on integrals and derivatives of fractional orders. It extends the usual ideas of differentiation and integration to orders that are not integers. The order of differentiation or integration in fractional calculus can be any real number, including non-integer numbers. For instance, taking the square root of a derivative or integral corresponds to a half-order derivative or integral. Numerous disciplines, including physics, engineering, economics, and signal processing, use fractional calculus.
Definition 1.3. [20,21] Let F∈L[Θ1,Θ2], where 0≤Θ1<Θ2. For α>0 and λ≥0, the tempered fractional integral operators Iα,λΘ+1F and Iα,λΘ−2F are defined as
and
respectively.
Definition 1.4. Let x,λ≥0 and α>0, then λ-incomplete gamma function is given by
If λ=1, then
The following portions of this work are inspired by the aforementioned findings: We found some H-H inequalities for subadditive functions and their product using tempered fractional integrals in Section 2. We propose various fractional inequalities for subadditive functions relevant to tempered fractional integral operators with the help of a new lemma in Section 3. In Section 4, we provide a few numerical examples and graphs with numerical estimations to support our findings. In Section 5, some conclusions and new ideas for future research are discussed.
2.
Main results
Let us take Q:=[0,∞), where Q∘:=(0,∞). Throughout this paper, we will use the above notations for our simplicity.
Theorem 2.1. Let F:Q→Q be a continuous subadditive function with Θ1,Θ2∈Q∘ and Θ1<Θ2. Then for λ≥0 and α>0, we have
Proof. Using the hypothesis of subadditive function F on Q, we have
Upon multiplication of (2.2) by δα−1e−λ(Θ2−Θ1)δ, and then integrating with respect to δ over [0,1], we get
Hence,
This concludes the first side (left) of (2.1). Next, for the other side (right) of (2.1), since F is subadditive on Q, one has
and
By adding (2.3) and (2.4), we get
Multiplying both sides of (2.5) by δα−1e−λ(Θ2−Θ1)δ, and following the same procedure as above, we complete the proof. □
Remark 2.1. Choosing λ=0 and α=1 in Theorem 2.1, we obtain Theorem 1.2.
Theorem 2.2. Let Φ,Ψ:Q→Q be two continuous subadditive functions with Θ1,Θ2∈Q∘ and Θ1<Θ2. Then for λ≥0 and α>0, we have
and
Proof. Using (2.2) and the hypothesis of subadditive functions Φ, and Ψ on Q, one has
and
Multiplying (2.8) and (2.9), we get
Multiplying both sides of (2.10) by δα−1e−λ(Θ2−Θ1)δ and integrating with respect to δ over [0,1], we obtain (2.6).
By subadditivity of Φ and Ψ on Q, we have
and
Multiplying inequalities (2.11) and (2.12), we get
Similarly,
Adding (2.13) and (2.14), we obtain
Multiplying both sides of (2.15) by δα−1e−λ(Θ2−Θ1)δ, and following the same procedure as above, we have (2.7). □
Remark 2.2. Choosing λ=0 and α=1 in Theorem 2.2, we obtain ([19], Theorem 4).
Theorem 2.3. Let F:Q→Q be a continuous subadditive function with Θ1,Θ2∈Q∘ and Θ1<Θ2. Then for λ≥0 and α>0, we have
Proof. From subadditivity of F, we have
Multiplying both sides of (2.17) by δα−1e−λ(Θ2−Θ1)δ, and then integrating over [0,1], we get
Hence,
which proves the left part of (2.16). Consequently, to prove the right part, we have
and
By adding (2.18) and (2.19), we obtain
Multiplying both sides of (2.20) by δα−1e−λ(Θ2−Θ1)δ, and following the same procedures as done in earlier theorems, we have the right part. □
3.
More midpoint type results
Lemma 3.1. Assume that F:Q→Q is a differentiable continuous function for Θ1,Θ2∈Q∘ and Θ1<Θ2. Then for λ≥0 and α>0, we have
Proof. Let us denote, respectively,
and
Then, we have
Using integration by parts, we get
Similarly,
From Definition 1.4, we get
Multiplying both sides of (3.2) by the factor (Θ2−Θ1)α+14γλ(α,Θ2−Θ1) and using above relation, we have the desired result (3.1). □
Theorem 3.1. Suppose that F:Q→Q is a differentiable continuous function with Θ1,Θ2∈Q∘ and Θ1<Θ2. If |F′|q for p>1 and 1p+1q=1 is a subadditive function, then for λ≥0 and α>0, we have
where
Proof. Under the assumption of Lemma 3.1, subadditivity of |F′|q on Q and Hölder's inequality, we have
The proof of Theorem 3.1 is completed. □
Corollary 3.1. Choosing |F′|≤K in Theorem 3.1, we get
Theorem 3.2. Assume that F:Q→Q is a differentiable continuous function with Θ1,Θ2∈Q∘ and Θ1<Θ2. If |F′|q for q≥1 is a subadditive function, then for λ≥0 and α>0, we have
where
Proof. Under the assumption of Lemma 3.1, subadditivity of |F′|q on Q and power-mean inequality, we have
The proof of Theorem 3.2 is completed. □
Corollary 3.2. Taking q=1 in Theorem 3.2, we have
Corollary 3.3. Choosing |F′|≤K in Theorem 3.2, we get
Remark 3.1. For suitable choices of α and λ in Theorems 3.1 and 3.2, one will able to get interesting integral inequalities.
4.
Numerical examples
It is shown that the functions F(δ)=e−δ and √δ for all δ>0 are subadditive. It can be observed that these graphs illustrate and confirm the correctness of our obtained inequalities.
Example 4.1. If we take subadditive function F(δ)=√δ in Theorem 2.1 for all δ>0, 0<α<1 and λ=1, then we observe the following numerical verification (see Table 1).
Example 4.2. If we take subadditive function F(δ)=e−δ in Theorems 2.1 and 2.3 for all δ>0, 0<α<1 and λ=1, then we observe the following numerical verifications (see Tables 2 and 3) and corresponding graphs (see Figures 1 and 2).
Example 4.3. Taking Φ(δ)=Ψ(δ)=e−δ in Theorem 2.2 for all δ>0, 0<α<1 and λ=1, then we observe the following numerical verifications (see Tables 4 and 5) and corresponding graphs (see Figures 3 and 4).
5.
Conclusions
Several new fractional H-H types for subadditive functions and their products are developed in this paper. As an ancillary finding, we also obtain inequalities for subadditive functions using tempered fractional integrals and a new identity. To confirm the veracity of our findings, we give several examples of subadditive functions, their graphical representations, and numerical calculations. For those interested in this topic and working on it, our findings utilizing the tempered fractional integral operators provide a number of new opportunities and make it possible for them to create additional approximations for many other varieties of operators.
Use of AI tools declaration
The authors declare that they have not used Artificial Intelligence (AI) tools in the creation of this article.
Acknowledgments
This work was supported by the Researchers Supporting Project number (RSP2024R153), King Saud University, Riyadh, Saudi Arabia.
Conflict of interest
The authors declare that they have no competing interests.