Abstract
In this article, we establish several new generalized Hardy-type inequalities involving several functions on time-scale nabla calculus. Furthermore, we derive some new multidimensional Hardy-type inequalities on time scales nabla calculus. The main results are proved by applying Minkowski’s inequality, Jensen’s inequality and Arithmetic Mean–Geometric Mean inequality. As a special case of our results, when we obtain refinements of some well-known continuous inequalities and when , the results which are essentially new.
Keywords:
Hardy-type inequality; time scales nabla calculus; weighted functions; inequalities; arithmetic mean–geometric mean inequality MSC:
26D10; 26D15; 34N05; 42B25; 42C10; 47B38
1. Introduction
In [1], Hardy proved that
where for and .
In [2], Hardy proved the continuous case of (1) in the following form
where and integrable over any finite interval and the constant in (1) and (2) is sharp.
In [3], Kaijser et al. established that if is a convex function on , then
where is a locally integrable positive function. In [4], Čižmešija et al. generalized (3) in the following form
where is a non-negative function, such that is locally integrable, is a convex function, and
In [5], Kaijser et al. explicated that if are positive functions, such that , is a convex function on , and
then
where is a function with values in and
Additionally, in [5] it is established that if and is a non-negative kernel, and are weighted functions, and
holds for all and if
where
In the last few decades, researchers discovered the time-scale calculus which unifies the continuous and discrete calculus. A time scale is an arbitrary, non-empty closed subset of the real numbers . Many authors established some new dynamic inequalities on ; see the books [6,7] and the papers [8,9,10,11,12].
In [13], Özkan et al. demonstrated that if is a non-negative function, such that exists as a finite number, is continuous and convex, and
then
They also proved that if is a non-negative function, and
then
holds for all
In [14], the authors proved the time-scale version of (4) as follows. Let be non-negative functions, is a continuous and convex function, and
Then,
where
Our aim in this study is to generalize (4) on time-scale nabla calculus of power in the form
where are positive constants. We will also establish the last inequality for several functions. Furthermore, we will prove the last inequality in multidimensions on time-scales nabla calculus.
2. Preliminaries and Basic Lemmas
For a time scale , we define the backward jump operator as Additionally, we define a mapping by , such that if is nabla differentiable at then For more details about calculus, see ([6,7]).
The nabla derivative of and (where ) are given by
and
Definition 1
([6]). A function is a nabla antiderivative of if holds . Hence, we have
Theorem 1
([6]). 0If and are ld-continuous functions, then
- (1)
- (2)
- (3)
The integration by parts formula on time scales nabla calculus [6] is
The Arithmetic Mean–Geometric Mean inequality is given by
where are non-negative functions.
In 2008, Ferreira et al. [15] proved Minkowski’s inequality on diamond alpha time scales. As a special case of this inequality (when ), we get Minkowski’s inequality on time-scale nabla calculus as follows.
Lemma 1
([15]). Let and be non-negative functions. Then,
for
Lemma 2
([16]). Let and ϖ be non-negative functions on and respectively. If then
Theorem 2
([16]). Let and be non-negative rd-continuous functions. Then,
where and
In [17], Jensen’s inequality is proved for the diamond time scale. In the case, this inequality can be written in nabla time-scale calculus as follows.
Lemma 3
([17]). Let be ld-continuous and Φ be continuous and convex. Then,
If Φ is a concave function, then (13) will be reversed.
Theorem 3
([17]). Let be ld-continuous and Φ be continuous and convex. Then,
where and
3. Main Results
Throughout this section, we will assume that the functions (without mention) are non-negative ld-continuous functions and the integrals in the statements of the theorems are convergent. We define the general Hardy operator as follows
where and and
Now, we state and prove our main results.
Theorem 4.
Let and be weighted functions, such that
Furthermore, assume that defined on and ξ is a convex function, such that
where are positive constants; then
holds for the non-negative function
Proof.
Corollary 1.
If and then
where
Remark 1.
If then and (17) reduces to
Remark 2.
If then and we have
where
Remark 3.
If we get the inequality (4) proved by Kaijser et al. [5].
The following theorem is proved for several functions.
Theorem 5.
Let and be as in Theorem 4, such that
Furthermore, assume that and are as in Theorem 4, such that
where are positive constants, then
holds for
Proof.
Applying (Arithmetic Mean–Geometric Mean) inequality (9), we see that
Then, we obtain
From (21), we obtain
Remark 4.
If we get Theorem 4.
Multidimensional Inequalities on Time Scales
In the following section, we define
where and
Theorem 6.
Let and be as in Theorem 4, such that
In addition, assume that are as in Theorem 4, such that
where are positive constants, then
holds for the non-negative function
Proof.
Remark 5.
If and then
where and
with
Remark 6.
If and then
where and
with
4. Conclusions
In this research, we generalize some new inequalities on time-scale nabla calculus. We will also establish some dynamic inequalities for several functions. Furthermore, we will establish these inequalities in multiple dimensions on time-scales nabla calculus. All of these inequalities can be proved by applying Minkowski’s inequality, Jensen’s inequality and Arithmetic Mean–Geometric Mean inequality. In the future, we hope to study these dynamic inequalities via conformable nabla fractional calculus on time scales.
Author Contributions
Software and Writing—original draft, A.I.S., G.A. and C.C.; Writing—review and editing M.Z. and H.M.R. All authors have read and agreed to the published version of the manuscript.
Funding
Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.
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.
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