Abstract
This manuscript develops the study of reverse Hilbert-type inequalities by applying reverse Hölder inequalities on . We generalize the reverse inequality of Hilbert-type with power two by replacing the power with a new power The main results are proved by using Specht’s ratio, chain rule and Jensen’s inequality. Our results (when ) are essentially new. Symmetrical properties play an essential role in determining the correct methods to solve inequalities.
Keywords:
reverse Hilbert-type inequalities; Specht’s ratio; time scales; reverse Hölder inequalities MSC:
26D10; 26D15; 34N05; 47B38; 39A12
1. Introduction
In [1], Hardy established that
where with and . The continuous form (see [2]) of (1) is
where are measurable functions such that and The constant in both (1) and (2) is sharp. In [2], Hardy showed that if and then
In [3], Hölder proved that
where and are positive sequences and such that The continuous form of (3) is
where such that and
In [4], Zhao and Cheung proved that if are continuous functions and is integrable on then
with
where is Specht’s ratio function (see [5]) and defined as
In [4], the authors proved that if and then
where
In addition, they proved the discrete case of (4) and established that
where and
In 2019, Zhao and Cheung [6] studied the reverse Hilbert inequalities and proved that if and are nonnegative and decreasing sequences of real numbers with then
where
and
where
and
In addition, they proved that if are nonnegative sequences and are positive sequences with , then
with
and
where are nonnegative, concave and supermultiplicative functions.
In [6], the authors proved that if are nonnegative sequenceswith then
with
Furthermore, many authors studied the inequalities of Hilbert-type, see [7,8,9,10,11,12,13,14,15].
In the last decades, the time scale theory was discovered which is a unification of the continuous calculus and discrete calculus. A time scale is an arbitrary nonempty closed subset of the real numbers . Many authors established some dynamic inequalities of Hilbert-type on time scales. For example, in 2021, AlNemer et al. [16] studied some reversed dynamic inequalities of Hilbert-type and proved that if , and are nonnegative and decreasing functions, then the inequality
holds for all ,with
and
Such that
and
where the function is the Specht ratio (see [5]) which is defined as follows:
The aim of this manuscript is to use reverse Hölder inequalities with Specht’s ratio on time scales to establish some new generalizations of reverse Hilbert-type inequalities. In particular, we generalize the inequality (8) by replacing the power 2 with a new power
The following is a breakdown of the paper’s structure. In Section 2, we cover some fundamentals of time scale theory as well as several time scale lemmas that will be useful in Section 3, where we prove our findings. As specific examples (when ), our major results yield (5)–(7) proven by Zhao and Cheung [6]. In addition, we obtain the inequality (8) proved by AlNemer et al. [16].
2. Definitions and Basic Lemmas
A time scale is defined as an arbitrary nonempty closed subset of the real numbers and the forward jump operator is defined by: The set of all such rd-continuous functions is ushered by and for any function , the notation denotes
The derivatives of and (where ) are given by
The integration by parts formula on is
The time scales chain rule is
where it is supposed that is continuously differentiable and is -differentiable. For further information on the time scale calculus, see [17,18].
Definition 1
([19]). A function is supermultiplicative if
Inequality (10) holds with equality if G is the identity map ( ). G is said to be a submultiplicative function if the last inequality has the opposite sign.
Lemma 1.
If λ is a nonnegative rd-continuous function and then
Proof.
Using the time scales chain rule on the term we obtain
Since , then we have (note ) that
Integrating (14) over from to we have
This means that
which is (11). □
Lemma 2
(Specht’s ratio [5]). Let be positive numbers, and Then,
where
Lemma 3
([5]). Let be as defined in Lemma 2. Then, is strictly decreasing for and strictly increasing for In addition, the following equations are true
Lemma 4
([20], when ). If such that are Δ-integrable on and let and , then
where and .
Lemma 5
(Jensen’s inequality). Let and . If φ: is rd-continuous and Ψ: is continuous and convex, then
Lemma 6.
Let be decreasing functions and Then,
and
Proof.
We have for that
and then (where ),
Since is decreasing, we have
thus the function is decreasing. Therefore, we have for that
Since the function is decreasing, we obtain that
Integrating the last inequality over from to we have
and then,
3. Main Results
Theorem 1.
Let and be nonnegative and decreasing functions. If with , then
where
and
such that
and
Proof.
Applying (11) with we obtain
Multiplying the last inequality by
we obtain
From Lemma 6, the last inequality becomes
Similarly, we have for and that
Dividing the two sides of (29) by and then taking the integration over t from to and the integration over from to we have
Similarly, we see that
Remark 1.
If we obtain (8) proved by AlNemer et al. [16].
Remark 2.
When and in Theorem 1, we obtain (5) as demonstrated in [6].
Remark 3.
As a special case of Theorem 1 (when ), we have that if and are nonnegative and decreasing functions and assume that with , then
where
and
Theorem 2.
Let be nonnegative and be positive functions. If are concave and supermultiplicative functions and with then
holds for all , with
and
Proof.
Using the fact that is a supermultiplicative function, applying Jensen’s inequality and then applying (16), we find
Similarly, we can obtain
Multiplying both sides of (35) and (36), respectively, by
and
and then multiplying these inequalities, we obtain
By dividing the two sides of (37) on and then taking the integration over from to and, then, the integration over t from to , we obtain
By using the integration by parts, we can see that
In addition, we can obtain that
Remark 4.
If and in Theorem 2, then we obtain (6) as demonstrated in [6].
By putting and in Theorem 2, we have the following theorem.
Theorem 3.
Assume that and are nonnegative functions and with Then, for all we have
where
and
Remark 5.
As a special case of Theorem 3, when , and we obtain (7) as was proved by Zhao and Cheung [6].
4. Conclusions
In this paper, we establish some new generalizations of reverse Hilbert-type inequalities by applying reverse Hölder inequalities with the Specht ratio function on time scales. We generalize a number of those inequalities to a general time-scale measure space. In addition to this, in order to obtain some new inequalities as special cases, we also extend our inequalities to a discrete and continuous calculus. In future work, we will continue to generalize more fractional dynamic inequalities by using Specht’s ratio, Kantorovich’s ratio and n-tuple fractional integral. In particular, such inequalities can be introduced by using fractional integrals and fractional derivatives of the Riemann–Liouville-type on time scales. It will also be very interesting to introduce such inequalities in quantum calculations.
Author Contributions
Software and writing—original draft, H.M.R., G.A. and A.I.S.; writing—review and editing, H.M.R., O.B. and M.Z. All authors have read and agreed to the published version of the manuscript.
Funding
This research project was funded by Deanship of Scientific research, Princess Nourah Bint Abdulrahman University.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Acknowledgments
This research project was funded by Deanship of Scientific Research, Princess Nourah bint Abdulrahman University, through the Program of Research Project Funding After Publication, Grant No (PRFA-P-42-14).
Conflicts of Interest
The authors declare no conflict of interest.
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