Abstract
Our work in this paper is based on the reverse Hölder-type dynamic inequalities illustrated by El-Deeb in 2018 and the reverse Hilbert-type dynamic inequalities illustrated by Rezk in 2021 and 2022. With the help of Specht’s ratio, the concept of supermultiplicative functions, chain rule, and Jensen’s inequality on time scales, we can establish some comprehensive and generalize a number of classical reverse Hilbert-type inequalities to a general time scale space. In time scale calculus, results are unified and extended. At the same time, the theory of time scale calculus is applied to unify discrete and continuous analysis and to combine them in one comprehensive form. This hybrid theory is also widely applied on symmetrical properties which play an essential role in determining the correct methods to solve inequalities. As a special case of our results when the supermultiplicative function represents the identity map, we obtain some results that have been recently published.
Keywords:
reverse Hilbert-type inequalities; Specht’s ratio; time scales; reverse Hölder inequalities MSC:
26D10; 26D15; 34N05; 47B38; 39A12
1. Introduction
In [1] (p. 253), Hardy established that
where with and . The continuous shape (see [2]) of (1) is called Hardy–Hilbert’s inequality and given by
where and are measurable nonnegative functions such that and . The constant in (1) and (2) sharp. In particular, when the inequality (2) is reduced to the classical Hilbert integral inequality:
In [2] (p. 253), the author proved the following extension of Hilber’s double-series (1). Let and Then,
The following continuous shape of (3) is also given in [2] (p. 254). Under the same condition with (3), we have
where in (3) and (4) depends on p and only.
As we all know, the classic Hölder inequality plays a very important and basic role in many areas of pure and applied mathematics. It is also a bridge to help solve problems in depth. In [3], Hölder established that
where and The continuous shape of (5) is
where s.t and
In [4], the researchers proved that, if and are nonnegative continuous functions on , then
with
where is the Specht’s ratio function ([5]) and defined by
In [4], the researchers established that, if and then
where
In addition, they established the discrete form of (8) as follows:
where and
In [6], the researchers proved that, if , and are nonnegative and decreasing sequences of real numberswith then
where
In addition, they proved that
where
and are nonnegative sequences with are positive sequences are nonnegative, concave and supermultiplicative functions.
In [6], the authors proved that
where
For some generalizations and extensions of reversed inequalities of Hilbert-type and Hölder-type on time scales, see ([7,8,9,10,11,12,13,14]).
The primary objective of this article is to develop some new generalisations of reverse Hilbert-type inequalities via supermultiplicative functions by using reverse Hölder inequalities with Specht’s ratio on (a time scale is defined as an arbitrary nonempty closed subset of the real numbers ).
The structure of the paper is summarised below. Section 2 covers some of the 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 particular examples (when ), our major findings are (10), as demonstrated by Zhao and Cheung [6].
2. Preliminaries
The forward jump operator is defined as
The set of all such rd-continuous functions is denoted by the space , and for any function , the notation denotes
The derivatives of and of two differentiable functions Z and are given by
The integration by parts formula on is
The time scales chain rule ([10] (Theorem 1.87)) is
where is continuously differentiable, and is differentiable. More information on time scale calculus can be found at ([10,11]).
Now, we will give some properties of multiplicative and supermultiplicative functions.
Definition 1.
A function is multiplicative if
Definition 2
([15]). A function is supermultiplicative if
where L is the identity map (i.e., ) and represents the multiplicative function. L is said to be a submultiplicative function if the last inequality has the opposite sign.
Lemma 1.
Let be nonnegative and Then,
Proof.
By using (15) on we obtain
Since , then we obtain (note ) that
Lemma 2
(Specht’s ratio [5]).Let be positive numbers, and Then,
where
Lemma 3
([5]). Let be defined as in Lemma 2. Then, is strictly decreasing for and strictly increasing for In addition, the following equations are true:
Lemma 4
([12], when α = 1). Let s.t. be integrable on . If and then
where and .
Lemma 5
(Jensen’s inequality). Assume that and . If and is continuous and convex, then
The inequality (23) is reversed when Ψ is continuous and concave.
Lemma 6.
Let , ψ be positive and decreasing functions, g are positive and nondecreasing functions and Furthermore, assume that φ are positive, increasing, concave and supermultiplicative functions. If with then
and
Proof.
For we have
and then (where )
Because is decreasing and , we can deduce from (26) that
Based on the knowledge is an increasing function and (27), we can conclude that
Then, we obtain (where and is nondecreasing) that
thus the function is decreasing. Therefore, we have for that
and then
Since the function is decreasing and , we obtain
and then
Throughout the article, we will assume that the functions are nonnegative rd-continuous functions on .
3. Principal Findings
Theorem 1.
Let , ψ be positive and decreasing functions and φ are positive, increasing, concave and supermultiplicative functions. If g are positive and nondecreasing functions and with then
holds for all , where
with
such that
and
Proof.
Denote
and
Applying (18) with gives us
By multiplying the previous inequality by
we have
Using the fact that f is nondecreasing and , we obtain
By Lemma 6, inequality (34) is
Likewise, for the decreasing function the nondecreasing function g and we obtain
From (35), we deduce that
Since is a positive, increasing and super-multiplicative function, we have
Then, by using the Jensen inequality on the right-hand side of (37) (where is a concave function), we obtain
Analogously, in the case of (36), we can see (where is a positive, increasing, concave and supermultiplicative function) that
Using the integration over t from z to and the integration over from z to respectively, we arrive at
In a similar vein, we note
Remark 1.
As a special case of Theorem 1, when , and we can obtain (10) demonstrated in [6].
Remark 2.
As a special case of Theorem 1, when and we can obtain the results demonstrated in [8].
Remark 3.
As a special case of Theorem 1, when we can obtain the results demonstrated in [16].
4. Conclusions
In this paper, we use reverse Hölder inequalities with Specht’s ratio on time scales to develop the study of reversed Hilbert-type inequalities. This aim holds by a study on some new generalizations of reversed Hilbert-type inequalities via supermultiplicative functions. In the future work, we can generalize dynamic inequalities of this article using a fractional Riemann–Liouville integral on time scale calculus, and we can present some of these dynamic inequalities on quantum calculus. It will be interesting to present dynamic inequalities in two or more dimensions.
Author Contributions
Software and Writing—original draft, H.M.R., G.A. and A.I.S.; Writing—review and editing H.M.R. and M.Z. All authors have read and agreed to the published version of the manuscript.
Funding
Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Acknowledgments
Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2022R45), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Hardy, G.H. Note on a theorem of Hilbert concerning series of positive term. Proc. Lond. Math. Soc. 1925, 23, 45–46. [Google Scholar]
- Hardy, G.H.; Littlewood, J.E.; Pólya, G. Inequalities, 2nd ed.; Cambridge University Press: Cambridge, UK, 1934. [Google Scholar]
- Hölder, O. Uber einen Mittelwerthssatz. Nachr. Ges. Wiss. Gott. 1889, 38–47. [Google Scholar]
- Zhao, C.J.; Cheung, W.S. Hölder’s reverse inequality and its applications. Publ. L’Inst. Math. 2016, 99, 211–216. [Google Scholar] [CrossRef]
- Tominaga, M. Specht’s ratio in the Young inequality. Sci. Math. Jpn. 2002, 55, 583–588. [Google Scholar]
- Zhao, C.J.; Cheung, W.S. Reverse Hilbert type inequalities. J. Math. Inequalities 2019, 13, 855–866. [Google Scholar] [CrossRef]
- Ahmed, A.M.; AlNemer, G.; Zakarya, M.; Rezk, H.M. Some dynamic inequalities of Hilbert’s type. J. Funct. Spaces 2020, 2020, 4976050. [Google Scholar] [CrossRef]
- AlNemer, G.; Saied, A.I.; Zakarya, M.; Abd El-Hamid, H.A.; Bazighifan, O.; Rezk, H.M. Some new reverse Hilbert’s inequalities on time scales. Symmetry 2021, 13, 2431. [Google Scholar] [CrossRef]
- Al Nemer, G.; Zakarya, M.; El-Hamid, H.A.A.; Agarwal, P.; Rezk, H. Some Dynamic Hilbert-type inequality on time scales. Symmetry 2020, 12, 1410. [Google Scholar]
- Bohner, M.; Peterson, A. Dynamic Equations on Time Scales: An Introduction with Applications; Birkhäuser: Boston, NA, USA, 2001. [Google Scholar]
- Bohner, M.; Peterson, A. Advances in Dynamic Equations on Time Scales; Birkhäuser: Boston, MA, USA, 2003. [Google Scholar]
- El-Deeb, A.A.; Elsennary, H.A.; Cheung, W. Some reverse Hölder inequalities with Specht’s ratio on time scales. J. Nonlinear Sci. Appl. 2018, 11, 444–455. [Google Scholar] [CrossRef]
- Saker, S.H.; Mahmoud, R.R.; Peterson, A. Weighted Hardy-type inequalities on time scales with applications. Mediterr. J. Math. 2016, 13, 585–606. [Google Scholar] [CrossRef]
- Saker, S.H.; Ahmed, A.M.; Rezk, H.M.; O’Regan, D.; Agarwal, R.P. New Hilbert’s dynamic inequalities on time scales. J Inequalities Appl. 2017, 20, 1017–1039. [Google Scholar] [CrossRef]
- Sandor, J. Inequalities for multiplicative arithmetic functions. arXiv 2011, arXiv:1105.0292. [Google Scholar]
- Zakarya, M.; Saied, A.I.; AlNemer, G.; Rezk, H.M. A study on some new reverse Hilbert-Type inequalities and its generalizations on time scales. J. Math. 2022, 2022, 6285367. [Google Scholar]
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |
© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).