Abstract
Our work is based on the multiple inequalities illustrated in 1967 by E. K. Godunova and V. I. Levin, in 1990 by Hwang and Yang and in 1993 by B. G. Pachpatte. With the help of the dynamic Jensen and Hölder inequality, we generalize a number of those inequalities to a general time scale. In addition to these generalizations, some integral and discrete inequalities will be obtained as special cases of our results.
MSC:
26D10; 26D15; 26E70; 34A40
1. Introduction
The following inequality [] is well-known in the literature as Opial’s inequality.
Theorem 1.
If δ is an absolutely continuous function on with , then
In 1967 E. K. Godunova and V. I. Levin [] proved the following two theorems which are a generalization of Opial’s inequality (1).
Theorem 2.
Let δ be real-valued absolutely continuous function on with Let f be real-valued convex and increasing function on with Then, the following inequality holds
Theorem 3.
Let δ be real-valued absolutely continuous function on with Assume f and g are real-valued convex and increasing functions on with Further let on and . Then, the following inequality holds
In 1990, Hwang and Yang [] established the following result:
Theorem 4.
Assuming and are continuous functions on with such that and exist and non-decreasing continuous functions on . Suppose x and y are absolutely continuous functions on , and . Then, for all , we get
where .
S. Hilger [], suggested time scales theory to unify discrete and continuous analysis. Continuous calculus, discrete calculus, and quantum calculus can be said as the three most common examples of calculus on time scales i.e., for continuous calculus for discrete calculus and for quantum calculus where . The book due to Bohner and Peterson [] on the subject of time scales briefs and organizes much of time scales calculus. For some Opial-type integral, dynamic inequalities and other types of inequalities on time scales, see the papers [,,,,,,,,,,,,,,,,,,,,,,,,,,]. More results on inequalities see, [,,,,,,,,,,,,,,,,,,,,].
The following essential relations on some time scales such as , , and will be used in the following section. Note that:
- (i)
- If , then
- (ii)
- If , then
- (iii)
- If , then
- (iv)
- If , then
Next is Hölder’s and Jensen’s inequality:
Lemma 1
(Hölder’s inequality []). Let . For f, , we have
where and .
Lemma 2
(Jensen’s inequality []). Let a, and c, . Assume that and are nonnegative with . If is a convex function, then
Lemma 3
(Chain rule []). Assume , is continuous, is delta-differentiable on , and is continuously differentiable. Then there exists c in the real interval with
In the proofs of our results, the following inequality will be used:
In this article, we prove some dynamic Opial-type inequalities involving convex functions on time scales. Our results generalize some of the mentioned results of Pachpatte [,], E. K. Godunova and V. I. Levin [] and Hwang and Yang [], in time scales. Furthermore, our results extend some existing dynamic Opial-type inequalities in the literature, and give some integral and discrete inequalities as special cases.
2. Main Results
Theorem 5.
Assuming is a time scale with Γ, , and are continuous functions on with such that and exist and non-decreasing continuous functions on . Suppose x and y are rd-continuous functions on , and . Then, for all , we get
where .
Proof.
For . Define and so that and . Thus,
Next, applying the dynamic Hölder’s inequality (1) on (11) with indices m and , we get
and similarly
Since , , , and are non-decreasing continuous on . Since , we get , and we find that
From Lemma 3 for , we get
and similarly
Remark 2.
In Corollary 2, if we take , then inequality (10) becomes
Remark 3.
Remark 4.
If , then inequality (17) gives E. K. Godunova and V. I. Levin’s inequality in [].
Corollary 3.
Assuming , , and in Theorem 5. Then, from (10), and Lemma 1 with indices and , we obtain
Corollary 4.
When and in (18), we obtain the following inequality
Corollary 5.
When , and in (18), we obtain the inequality of Hua []
Moreover, in (20), equality holds if and only if .
Corollary 6.
If , then (18), gives the inequality of Yang [].
Corollary 7.
Assuming is rd-continuous on with , and let is non-increasing bounded on . By using , , and and . Then, we get from Theorem 5, the following inequality
However, since
it follows that
By applying the Cauchy–Schwarz inequality, we get that
Remark 5.
When , the inequality (22), reduces to Yang inequality []
Corollary 8.
Take , , and in Theorem 5, the inequality (10) becomes
From Lemma 1 with indices , such that , we obtain
Remark 6.
If , then (23), gives the inequality of Maroni [].
Theorem 6.
Under the hypotheses of Theorem 5. Let and be defined on with and . Further, let be convex and increasing on . Then, for all , the following inequality holds
where defined as in Theorem 5.
Proof.
Dynamic Jensen inequality (2) provides
Further, since is increasing, we have
Similarly, we have
This gives our claim. □
Remark 7.
When in Theorem 6, then, by the relation (4), we get the inequality of Hwang and Yang [].
Remark 8.
In Corollary 10, if we take , then inequality (25) becomes
Remark 9.
When , if we take and , in the inequality (25), we get Pachpatte inequality []
Remark 10.
Taking and in inequality (28), we get the Pachpatte inequality []
Corollary 11.
Suppose is a time scale, α, β, , and f, g are defined as in Theorem 5. Furthermore, Assume x and y are rd-continuous functions on such that and . Then, we get
where .
Proof.
Let , the functions x and y satisfy the conditions of Theorem 5 on . Thus, inequality (10) holds. Next, in the interval , the functions x and y are rd-continuous, and . Thus, by defining , , and following an argument similar to Theorem 5, we obtain
where . A combination of the inequalities (10) and (30), we get
for , we find that , where , then . Then, by substituting in (31), we get
Since g is non-decreasing function, we have
This gives our claim (29). □
Remark 11.
In Corollary 12, if we take , then inequality (29) becomes
Corollary 14.
In Corollary 11. For , we can get the following inequality
Remark 12.
Taking , then (38) gives Yang inequality []
Theorem 7.
Under the hypotheses of Theorem 5. Assuming that , and , , and , and and are convex and increasing functions on . Then, we get
Proof.
For , we define and so that and .
Thus,
Then, we obtain
Thus, from Lemma 2, we get
Using the above inequalities, we get
Since f, r, , and are increasing and , we get
Then by substituting in (40), we get
From Lemma 3 for , we get
This gives our claim. □
Remark 14.
In Corollary 16, if we take , then inequality (39) becomes
Remark 15.
For , , and , the inequality (39) becomes
Corollary 18.
With the assumptions of Theorem 7. Suppose , and . Assuming is increasing and convex on . Then, we get
3. Conclusions
In this paper, with the help of the dynamic Jensen inequality, dynamic Hölder inequality and a simple consequence of Keller’s chain rule on time scales, we generalized a number of Opial-type inequalities to a general time scale. Besides that, in order to illustrate the theorems for each type of inequality applied to various time scales such as , , and as a sub case of . For future studies, researchers may obtain some different generalizations for dynamic Opial inequality and its companion inequalities by using the results presented in this paper.
Author Contributions
A.A.E.-D. contributed in conceptualization, methodology, resources, validation and original draft preparation. D.B. contributed in investigation, formal analysis, review, editing and funding acquisition. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Conflicts of Interest
The authors declare no conflict of interest.
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