1. Introduction
The inequalities derived by Hermite and Hadamard for convex functions hold significant importance in the literature (refer to, for instance, [
1] p. 137). These inequalities assert that if
is a convex function defined on the interval
of real numbers, and
with
, then
Both inequalities are valid in the opposite direction if f exhibits concavity. It is worth mentioning that Hadamard’s inequality can be considered a further specification of convexity and can be readily derived from Jensen’s inequality; see [
2,
3]. Hadamard’s inequality for convex functions has garnered renewed interest in recent years, leading to a notable array of enhancements and extensions. These can be explored in various sources, such as [
4,
5,
6,
7,
8], and the references provided therein.
The classical Hermite–Hadamard inequality provides estimates for the mean value of a continuous convex function
.
For every and within the interval and for every belonging to , we define as concave if its is convex.
On the other hand, an issue in astrophysics, particularly regarding stellar absorption, led to Edward Arthur Milne [
9] establishing the following intriguing integral inequality in 1925, inspired by a paper by Rosseland, a Norwegian astrophysicist, on this subject from 1924.
This Milne inequality applies to all positive and integrable functions
and
defined on the interval
such that
In 1938, Ostrowski [
10] explored the following compelling integral inequalities:
Let
be a differentiable function on
with
. If
and
, for all
, then
The renowned integral inequalities of the Ostrowski, Čebyšev, and Grüss varieties permeate numerous branches of mathematics (for historical context and generalizations, refer to the seminal monograph [
11], as well as works [
12,
13]). The Čebyšev and Ostrowski-type inequalities, closely intertwined (refer to [
14] for elaboration), hold significance in various mathematical applications and have garnered considerable attention from scholars. Ujević [
15] derived the subsequent Ostrowski-type inequality:
where
is a differentiable function with
and
is the best possible. For further information on additional Ostrowski-type inequalities, we direct interested readers to [
16,
17,
18,
19,
20,
21].
Developing a variety of integral inequalities has become a contemporary focus. In recent years, significant advancements have been achieved through the utilization of diverse integrals, including the Sugeno integral [
22,
23], the pseudo integral [
24], and the Choquet integral [
25], among others. Interval-valued functions [
26], which extend beyond traditional functions, have emerged as a crucial mathematical area, particularly in addressing practical issues, notably in mathematical economics [
27]. Recent studies have extended certain classical integral inequalities to encompass interval-valued functions.
Costa et al. [
28] introduced novel interval adaptations of Minkowski and Beckenbach’s integral inequalities. They generalized Hermite–Hadamard, Jensen, and Ostrowski-type inequalities within this framework [
29]. Additionally, they addressed Hermite–Hadamard and Hermite–Hadamard-type inequalities using interval-valued Riemann–Liouville fractional integrals [
30]. Zhao et al. [
31,
32,
33] investigated Chebyshev-type inequalities, Opial-type integral inequalities, and Jensen and Hermite–Hadamard-type inequalities for interval-valued functions, utilizing the concepts of gH-differentiability or h-convexity. Budak et al. [
34] derived innovative fractional inequalities of the Ostrowski type for interval-valued functions, drawing on the definitions of gH-derivatives. Basic concepts related to fuzzy numbers and fuzzy Aumman’s integral are in the following literature: [
35,
36,
37] and the references therein. Nanda [
38] was the first to introduce the concept of convexity in fuzzy environments. Breckner [
39] was the first to introduce the concept of continuity as well as to propose the class of convex mappings which is known as interval convex mapping. Khan et al. [
40,
41,
42,
43] introduced log-h-convex and (
,
)–convex fuzzy-interval-valued functions by using fuzzy Kulisch–Miranker, up- and down-, and left- and right-order relations as a distinct class of convex fuzzy-interval-valued functions. This class facilitated the establishment of Jensen and Hermite–Hadamard inequalities; see [
44,
45,
46] and the references therein.
Notice that the left Hermite–Hadamard inequality can be approximated using Ostrowski’s inequality, well known for its estimation of the deviation of smooth function values from their mean. Drawing from current research trends, we once more examine the category of
-Godunova–Levin convex functions. This article’s primary aim is to establish connections between
-Godunova–Levin convex functions and integral inequalities resembling Ostrowski’s. Additionally, we derive Ostrowski-like inequalities from other sets of Godunova–Levin convex functions, which are essentially special instances of our principal findings. Furthermore, we discuss some applications of our primary results to special means. We anticipate that the concepts and methodologies presented herein will inspire further exploration in this domain; see [
47,
48,
49,
50,
51,
52] and the references therein.
The rest of the paper is structured as follows: In
Section 2, we present a literature review. In
Section 3, we introduce a novel definition of an
-Godunova–Levin convexity over a fuzzy codomain and derive several classical special cases of this class of convex fuzzy mappings. The Milne-type inequality has been introduced in
Section 4. In
Section 5, we established the Ostrowski-type inequality for
-Godunova–Levin convexity. In
Section 6, other main findings related to Hermite–Hadamard-type inequalities and associated corollaries are presented, and some illustrative examples are also examined in this section. Lastly, we summarize the results and outline potential avenues for future research in
Section 7.
2. Preliminaries
Firstly, we recall some basic notations that will be helpful in this section such as the following:
Gamma and Beta functions are, respectively, characterized as
for
for
,
.
The integral representation of the hypergeometric function is
for
,
,
.
Consider
as the set comprising all closed and bounded intervals of
, and let
belong to
, defined as
It is named a positive interval
if
. The definition of
, which represents the set of all positive intervals, is
Let
and
be defined by
Subsequently, the Minkowski difference
, addition
, and multiplication
for
belong to
and are delineated as follows:
Remark 1. For given the relation is defined on by if and only if for all is a fuzzy-order relation. The relation is coincident to on ; see [46]. This fuzzy-order relation is known as fuzzy Kulisch–Miranker order. For
the Hausdorff–Pompeiu distance between intervals
and
is defined by
It is a familiar fact that
is a complete metric space [
35,
36,
37].
We will briefly review some essential concepts regarding fuzzy sets and fuzzy numbers since we will rely on the standard definitions of these sets.
Please note that we refer to and as the set of all fuzzy subsets and fuzzy numbers of .
Definition 1 [35]. Given , the level sets or cut sets are given by for all and by . These sets are known as -level sets or -cut sets of .
Proposition 1 [28]. Let . Then, relation is given on by when and only when , for every which are left- and right-order relations or fuzzy Kulisch–Miranker-order relations.
Proposition 2 [49]. Let . Then, relation is given on by when and only when for every which is the order relation on .
Remember the approaching notions, which are offered in the literature. If
and
, then, for every
the arithmetic operations addition “
, multiplication “
, and scaler multiplication “
are defined by
over
.
Aumann Integral Operators for Interval and ··Ms
Now, we define and discuss some properties of Aumann integral operators for interval and ··s.
Theorem 1 [35,37]. If is an interval-valued mapping () which satisfies , then is an Aumann integrable (IA integrable) over when and only when and both are integrable over such that The literature suggests the following conclusions; see [36,38,46]: Definition 2 [46]. A fuzzy-number-valued map is named fuzzy number mapping (··). For each its s are classified according to their -levels. are given by for all Here, for each the end-point real mappings are called lower and upper mappings of .
Definition 3. Let be an · ·. Then, the fuzzy integral of over denoted by , is given level-wise byfor all where denotes the collection of Riemannian integrable mappings of s. The ·· is -integrable over if Note that, if are Lebesgue-integrable, then is fuzzy Aumann-integrable mapping over ; see [46].
Theorem 2 [37]. Let be an ··; s are classified according to their -levels. are given by for all and for all Then, is -integrable over if and only if and are both -integrable over . Moreover, if is -integrable over thenfor all For all denotes the collection of all -integrable ··s. The family of all -integrable ··s over is denoted by
Breckner discussed the emerging idea of interval-valued convexity in [
39].
A
is called convex
if
for all
, where
is the collection of all real-valued intervals. If (19) is reversed, then
is called concave.
Definition 4 [38]. The ·· is called convex ·· on iffor all where for all If (20) is reversed, then is called concave ·· on .
is affine if and only if it is both convex and concave ··.
3. -Godunova–Levin Convex ··
In this section, we start with the main definition of -Godunova–Levin convexity over the fuzzy domain that will be helpful for the upcoming results.
Definition 5. Let be a convex set and such that . Then, the mapping is said to be -Godunova–Levin convex ··
on iffor all where The mapping is said to be -Godunova–Levin concave ·· on if inequality (21) is reversed. Moreover, is known as -Godunova–Levin affine ·· on iffor all where .
Remark 2. The -Godunova–Levin convex ··s have some very nice properties, similar to convex ··.
- (1)
If is an -Godunova–Levin convex ··, then is also -Godunova–Levin convex for .
- (2)
If and both are -Godunova–Levin convex ··s, then is also -Godunova–Levin convex ··.
Here, we will go through a few unique exceptional cases of -Godunova–Levin convex ··s.
- (i)
If
then
-Godunova–Levin convex
·
·
becomes
-Godunova–Levin convex
·
·
, that is,
- (ii)
If
then
-Godunova–Levin convex
·
·
becomes Godunova–Levin convex
·
·
—see [
41]—that is,
- (iii)
If
then
-Godunova–Levin convex
·
·
becomes Godunova–Levin
-
·
·
, that is,
Note that there are also new special cases (i) and (iii) as well.
Theorem 3. Let be convex set, non-negative real-valued function such that and let be an ··, and s are classified according to their -levels, such that are given byfor all and for all . Then, is an -Godunova–Levin convex on if and only if, for all and are -Godunova–Levin convex mappings. Proof .
Assume that for each
and
are both
-Godunova–Levin convex on
, respectively. Then, we have
and
Then, by (23), (8), and (9), we obtain
that is,
Hence, is an -Godunova–Levin convex ·· on
Conversely, let
be
-Godunova–Levin convex
·
·
on
Then, for all
and
we have
Therefore, from (21), we have
Again, from (23), (8) and (9), we obtain
for all
and
Then, by
-Godunova–Levin convexity of
, we have for all
and
such that
and
for each
Hence, the result follows. □
Remark 3. If with then -Godunova–Levin convex ·· reduces to the -Godunova–Levin convex function.
If with and with , then -Godunova–Levin convex ·· reduces to the -Godunova–Levin convex function.
If with and , then -Godunova–Levin convex ·· reduces to the Godunova–Levin convex function.
If with and , then -Godunova–Levin convex ·· reduces to the -convex function.
Example 1. We consider for and the ·· defined by Then, for each we have , since end-point functions are -Godunova–Levin convex and -Godunova–Levin concave functions for each , respectively. Hence, is an -Godunova–Levin convex ··.
Definition 6. Let be an ··, and s are classified according to their -levels, such that are given byfor all and for all . Then, is a lower -Godunova–Levin convex (-Godunova–Levin concave) ·· on if and only if, for all is a -Godunova–Levin convex (-Godunova–Levin concave) mapping and is a -Godunova–Levin affine mapping. Definition 7. Let be an ··, and s are classified according to their -levels such that are given byfor all and for all . Then, is an upper -Godunova–Levin convex (-Godunova–Levin concave) ·· on if and only if, for all is an -Godunova–Levin affine mapping and is an -Godunova–Levin convex (-Godunova–Levin concave) mapping. Remark 4. If , then both concepts, “-Godunova–Levin convex ··” and classical “-Godunova–Levin convex ··, behave alike when is a lower -Godunova–Levin convex ··.
Both concepts, “-Godunova–Levin convex interval-valued mapping” and “left and right -Godunova–Levinconvex interval-valued mapping” are coincident when is a lower -Godunova–Levin convex ·· with .
4. Fuzzy Version of Milne-Type Inequality
This section just proposes the following new estimation of Milne-type inequality in a fuzzy environment.
Theorem 4. Let be two ··s, and s are classified according to their -levels such that, are given, respectively, by and for all and for all . Then, Proof. Since, for each
we have
and hence the required result. □
The subsequent outcome indicates that the interval integral inequality stated in Theorem 4 entails the classical Milne’s inequality (3).
Corollary 1. Let and be two integrable ··s from to , such that and for all for all . Then, 5. Fuzzy Version of Ostrowski-Type Inequality via -Godunova–Levin ··s
Here, an Ostrowski-type inequality was formulated in conjunction with several illustrations for Godunova–Levin functions within a broader category.
The subsequent lemma aids in achieving our goal.
Lemma 1. Let be a differentiable function on with , where . If is integrable over , then Proof. Integration by parts finalizes the proof. □
Now, employing Lemma 1, we derive the principal outcomes.
Theorem 5. Let be a differentiable function on with , where , and let be a integrable over . If and is an -Godunova–Levin ··, with , then forfor all Proof. In accordance with Lemma 1 and when
is an
-Godunova–Levin
·
·
, for
, we have
and
From the above equations, we have
and
As a result, we obtain
and
That is,
Example 2. We consider for , and the ·· defined by Then, for each we have . Since left and right end-point mappings, , are -Godunova–Levin convex mappings for each , is an -Godunova–Levin convex ··. We clearly see that .
Applying the Ostrowski-type inequality, we have the following:
Since
, we have
On the other hand, for
, we have
Since
, we have
6. Fuzzy-Valued Hermite–Hadamard Inequalities
The fuzzy-valued Hermite–Hadamard inequalities for -Godunova–Levin convex ··s are established in this section. Additionally, several instances are provided to support the theory produced in this study’s application.
Theorem 6. Let be an -Godunova–Levin convex ·· with non-negative real-valued function and , and s are classified according to their -levels such that are given by for all and for all . If , then If is an -Godunova–Levin concave ··, then (24) is reversed. Proof. Let
be a
-Godunova–Levin convex
·
·
. Then, for
, we have
If
, then we have
Let
and
. Then, from the above inequality, we have
Therefore, for every
, we have
In a similar way as above, we have
Combining (26) and (27), we have
Hence, the required result is obtained. □
Note that, by using same steps, Formula (25) can be proved with the help of an -Godunova–Levin concave ··.
Remark 5. If , then Theorem 6 simplifies to the outcome for the -convex ··, which is also a new one: If , then Theorem 6 simplifies to the outcome for a convex ·· which is also a new one: If , then Theorem 6 simplifies to the outcome for a -convex ··, which is also a new one: If with , then Theorem 6 simplifies to the outcome for the classical -convex function; see [49]: If with and , then Theorem 6 simplifies to the outcome for the classical convex function; see [49]: If with , then Theorem 6 simplifies to the outcome for the classical -convex function; see [50]: If with and , then Theorem 6 simplifies to the outcome for the classical -convex function; see [50]: If with and , then Theorem 6 simplifies to the outcome for the classical convex function: If with and , then Theorem 6 simplifies to the outcome for the classical -convex function: Example 3. We consider for , and the ·· is defined by, Then, for each
we have
. Since left and right end-point mappings,
, are
-Godunova–Levin convex mappings for each
,
is an
-Godunova–Levin convex
·
·
. We clearly see that
. Now, we compute the following:
for all
This means
Similarly, it can be easily shown that
for all
such that
From which, we have
that is
for all
Theorem 7. Let be an -Godunova–Levin convex ·· with non-negative real-valued function and and s are classified according to their -levels such that are given by for all and for all . If , then If is an -Godunova–Levin concave ··, then (37) is reversed. and ,
Proof. Taking
we have
Therefore, for every
, we have
In consequence, we obtain
It follows that
In a similar way as above, we have
Combining (38) and (39), we have
Therefore, for every
, we have
that is
hence, the result follows. □
Example 4. We consider for , and the ·· defined by, as in Example 3, then is an -Godunova–Levin convex ··. We have and . We now compute the following: Then, we obtain the following:
Hence, Theorem 7 is verified.
The novel fuzzy Hermite–Hadamard inequalities for the product of two -Godunova–Levin convex ··s are found in the results.
Theorem 8. Let be two -Godunova–Levin convex ··s with non-negative real-valued functions and and s are classified according to their -levels such that are given by and for all and for all . If , and , then The (42) is reversed for an -Godunova–Levin concave ··.
Where and and
Proof. Let
be two
-Godunova–Levin convex and
-Godunova–Levin convex
·
·
s. Then, we have
and
From the definition of an
-Godunova–Levin convex
·
·
, it follows that
and
, so
Integrating both sides of the above inequality over [0, 1] we obtain
Thus,
and the theorem has been established. □
Example 5. We consider for , and the ··s is defined by Then, for each
we have
and
The end-point functions
and
,
are
-Godunova–Levin convex functions for each
. Hence,
both are
-Godunova–Levin convex
·
·
s. We now compute the following:
for each
which means
Hence, Theorem 8 is demonstrated.
Theorem 9. Let be two -Godunova–Levin convex and - Godunova–Levin convex ··s with non-negative real-valued functions , respectively, and respectively, and s are classified according to their -levels such that are given, respectively, by and for all and for all . If , then where and and
Proof. By hypothesis, for each
we have
Integrating over
we have
that is
Hence, the required result is obtained. □
Example 6. We consider for , and the ··s as in Example 5. Then, for each we have and , and are -Godunova–Levin convex and -Godunova–Levin convex ··s, respectively. We have and , . We now compute the following:for each which meanshence, Theorem 9 is demonstrated. The H-H Fejér inequalities for -Godunova–Levin convex ··s are now presented. The second H-H Fejér inequality for the -Godunova–Levin convex ·· is firstly obtained.
Theorem 10. Let be an -Godunova–Levin convex ·· with , and s are classified according to their -levels such that are given by for all and for all . If and symmetric with respect to then Proof. Let
be an
-Godunova–Levin convex
·
·
. Then, for each
we have
and
After adding (45) and (46), and integrating over
we obtain
Since
is symmetric, then
Then, from (45) and (46), we have
that is
hence
Now, generalizing the first H-H Fejér inequalities for classical Godunova–Levin convex functions, we build the first H-H Fejér inequality for an -Godunova–Levin convex ··. □
Theorem 11. Let be an -Godunova–Levin convex ·· with , and s are classified according to their -levels such that are given by for all and for all . If and symmetric with respect to and , then Proof. Since
is an
-Godunova–Levin convex, then for
we have
Since
, then by multiplying (48) by
and integrating it with respect to
over
we obtain
Then, from (50) and (51), (49) we have
from which, we have
that is
This completes the proof. □
Remark 6. From Theorem 10 and 11, we clearly see the following:
If , then we acquire the inequality (24).
Let
with
and
. Then, from (42) and (47), we acquire the following inequality; see [
48]:
If
is a lower Godunova–Levin convex
·
·
on
and
, then we derive the following subsequent inequality; see [
41]:
If
is a lower Godunova–Levin convex
·
·
on
with
and
, then from (42) and (47), we derive the following subsequent inequality; see [
42]:
If
is a lower Godunova–Levin convex
·
·
on
with
and
, then from (42) and (47), we derive the following subsequent inequality; see [
42]:
Let
and
with
. Then, from (42) and (47), we obtain the following classical Fejér inequality:
Example 7. We consider for , and the ·· defined by Then, for each
we have
. Since end-point mappings
are
-Godunova–Levin convex mappings for each
,
is an
-Godunova–Levin convex
·
·
. If
then
, for all
.
and
. Now, we compute the following:
From (57) and (58), we have
for all
Hence, Theorem 10 is verified.
From (59) and (60), we have
Hence, Theorem 11 has been verified.
7. Conclusions
The -Godunova–Levin convex ·· and fuzzy Aumann integral operators represent pivotal tools in addressing Hermite–Hadamard inequality problems. In this paper, we introduce a more comprehensive Godunova–Levin convex ··, which extends several well-known classical convexities. The refinements of Milne, Ostrowski, and Hermite–Hadamard-type inequalities are introduced over -Godunova–Levin convex ··s. Moreover, some exceptional cases are also achieved. Nontrivial numerical examples are also given for the validation of main outcomes. Interested researchers can explore this article concept in fuzzy fractional calculus. In future, we will try to explore this concept for fuzzy fractional calculus and fuzzy q-fractional calculus.