Abstract
In this paper, some new Gronwall-Bellman-type nonlinear dynamic inequalities containing integration on infinite intervals on time scales are established, which provides new bounds on unknown functions and can be used as a handy tool in the qualitative analysis of solutions of certain dynamic equations on time scales.
MSC:26E70, 26D15, 26D10.
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1 Introduction
In the analysis of solutions of certain differential, integral and difference equations, if the solutions are unknown, then it is necessary to make estimate for their bounds. The Gronwall-Bellman inequality [1, 2] and its various generalizations which provide explicit bounds for solutions of differential, integral and difference equations have proved to be of particular importance in this aspect, and much effort has been made to establish such inequalities over the years (for example, see [3–10]). On the other hand, since Hilger [11] initiated the theory of time scales as a theory capable to contain both difference and differential calculus in a consistent way, many authors have expounded on various aspects of the theory of dynamic equations on time scales (for example, see [12–20] and the references therein). In these investigations, many authors have paid considerable attention to inequalities on time scales, and a lot of inequalities including Gronwall-Bellman type inequalities on time scales have been established (for example, see [15–27] and the references therein). But Gronwall-Bellman type nonlinear delay dynamic inequalities on time scales have been paid little attention in literature so far. Recent results in this direction include the works of Li [18], Ma et al. [23], Saker [24], and Feng et al. [25, 26], while nobody has undertaken research into Gronwall-Bellman type nonlinear dynamic inequalities containing integration on infinite intervals on time scales to our best knowledge. Besides, in order to fulfill the analysis of boundedness of the solutions of some dynamic equations, for example, the equations and , which contain integration on infinite intervals on time scales, it is necessary to seek some new Gronwall-Bellman type nonlinear dynamic inequalities containing integration on infinite intervals on time scales so as to obtain desired results.
In this paper, we will establish some new Gronwall-Bellman type nonlinear dynamic inequalities containing integration on infinite intervals on time scales, which provide new bounds on unknown functions in some certain dynamic equations on time scales.
First, we will give some preliminaries on time scales and some universal symbols for further use. Throughout the paper, denotes the set of real numbers and , while denotes the set of integers. For two given sets G, H, we denote the set of maps from G to H by . A time scale is an arbitrary nonempty closed subset of the real numbers. In this paper, denotes an arbitrary time scale and , where . On we define the forward and backward jump operators and such that , . The graininess is defined by . A point is said to be left-dense if and and right-dense if and , left-scattered if and right-scattered if . The set is defined to be if does not have a left-scattered maximum, otherwise it is without the left-scattered maximum. A function is called rd-continuous if it is continuous in right-dense points and if the left-sided limits exist in left-dense points, while f is called regressive if . denotes the set of rd-continuous functions, while denotes the set of all regressive and rd-continuous functions, and .
Definition 1.1 For some , and a function , the delta derivative of f is denoted by and satisfies
where , and is a neighborhood of t. The function f is called delta differential at t.
The nabla derivative of f is denoted by and satisfies
where , and is a neighborhood of t.
Remark 1.1 If , then and become the usual derivative , while , if , which represent the forward and backward difference respectively.
Definition 1.2 If , , then F is called an antiderivative of f, and the Cauchy integral of f is defined by
Similarly, if , then
The following two theorems include some important properties for delta derivative, nabla derivative, and the Cauchy integral on time scales.
Theorem 1.1 ([27])
If , and , then
-
(ii)
(i)
-
(ii)
If f, g are delta differentials at t, then fg is also delta differential at t, and
Theorem 1.2 ([27])
If , , and , then
-
(i)
,
-
(ii)
,
-
(iii)
,
-
(iv)
,
-
(v)
,
-
(vi)
if for all , then .
Remark 1.2 Theorem 1.2 also holds for nabla derivative. If , then all the conclusions of Theorem 1.2 still hold.
Definition 1.3 The cylinder transformation is defined by
where Log is the principal logarithm function.
Definition 1.4 For , the exponential function is defined by
Definition 1.5 If , , we define
Remark 1.3 If , then for ,
If , then for ,
The following two theorems include some known properties on the exponential function.
Theorem 1.3 ([28])
If , then the following conclusions hold:
-
(i)
, and ,
-
(ii)
,
-
(iii)
if , then ,
-
(iv)
if , then ,
-
(v)
,
where .
Remark 1.4 If , then Theorem 1.3(v) still holds.
Theorem 1.4 ([28])
If , and fix , then the exponential function is the unique solution of the following initial value problem:
For more details about the calculus of time scales, we refer the reader to [29].
2 Main results
For the sake of convenience, we always assume and in the rest of this paper.
Lemma 2.1 Suppose . , that is, , , and furthermore, assume . u is delta differential at , and , . Then
implies
Proof Let
then we have
and
that is,
Since , then from Theorem 1.3(iv), we have , and furthermore, from Theorem 1.3(iii), we obtain .
According to Theorem 1.1(ii),
On the other hand, from Theorem 1.4, we have
So combining (2.5), (2.6) and Theorem 1.3 yields
Substituting t with s and an integration for (2.7) with respect to s from α to ∞ yield
Since , then . Considering , and , by (2.4) and (2.8), we have
which is followed by
Since is arbitrary, then substituting α with t and combining (2.3), we can obtain the desired inequality. □
Lemma 2.2 Under the conditions of Lemma 2.1, furthermore, if is decreasing, then we have
Proof Since is decreasing on , then from (2.2), we have
On the other hand, from [[23], Theorems 2.39 and 2.36(i)], for some , we have
Then letting in (2.12), we obtain
Combining (2.11) and (2.13), we obtain the desired inequality. □
Lemma 2.3 ([30])
Assume that , and , then for any ,
Now, we consider the delay dynamic inequality of the following form:
where , and a is decreasing. with , , is a constant, is nondecreasing, and ω is submultiplicative, that is, holds , .
Theorem 2.1 If satisfies inequality (2.14), then we have
provided that , and , where G is an increasing bijective function, and
Proof Let the right side of (2.14) be . Then
and
Furthermore,
According to , a suitable application of Lemma 2.2 to (2.18) yields
Fix , and let . Define
Then
and
that is,
On the other hand, for , if , then
If , then
where ξ lies between and . So we always have . Using the statements above, we deduce that
Substituting t with s in (2.22) and an integration with respect to s from t to ∞ yield
Consider G is strictly increasing and , then it follows
Combining (2.16), (2.21) and (2.23), we have for
Setting in (2.24) yields
Since is selected arbitrarily, after substituting T with t in (2.25) the proof is complete. □
If we let in Theorem 2.1, then we have the following corollary.
Corollary 2.1 Under the conditions of Theorem 2.1 with , if for , satisfies the following inequality:
then
provided that , and .
Since is an arbitrary time scale, then if we take for some peculiar cases in Theorem 2.1, then we can obtain some corollaries immediately. Especially, if we take or , then we obtain continuous and discrete analyses respectively, which are shown in the following two corollaries.
Corollary 2.2 Suppose , , and . , and a, b are decreasing on . , , , ω is defined the same as in Theorem 2.1. If for , satisfies
then
provided that .
Corollary 2.3 Suppose , , and . , and a, b are decreasing on . , , , ω is defined the same as in Theorem 2.1. If for , satisfies
provided that , and .
Second, we study the following delay dynamic inequality on time scales:
where , and b is decreasing, u, a, f are defined the same as in Theorem 2.1, is nondecreasing, , .
Theorem 2.2 If satisfies inequality (2.28), then
where G is defined the same as in Theorem 2.1.
Proof Let the right side of (2.28) be . Then we have
and
Furthermore,
Let be fixed, and denote
Consider a, b are decreasing on , then for , we have
Moreover,
Similar to Theorem 2.1, we have
Substituting t with s in (2.35) and an integration with respect to s from t to ∞ yield
Consider G is strictly increasing, and , then (2.36) is followed by
Combining (2.30), (2.34) and (2.37) yields
Setting in (2.38), we obtain
Since is selected arbitrarily, then after substituting T with t in (2.39), we obtain the desired inequality (2.29). □
Considering is an arbitrary time scale, if we take for some peculiar cases in Theorem 2.2, we immediately get the following two corollaries.
Corollary 2.4 Suppose , , and . , and a, b are decreasing on . , , ω is defined as in Theorem 2.2. If satisfies
then
Corollary 2.5 Suppose , , and . , and a, b are decreasing on . , , ω is the same as in Theorem 2.2. If satisfies
then
In Theorem 2.2, if we change the conditions for ω, then we can obtain another bound for the function , which is shown in the following theorem.
Theorem 2.3 Suppose with a, b decreasing, is nondecreasing, subadditive and submultiplicative, that is, , , we always have and . τ, α, ϕ are the same as in Theorem 2.2. If is a strictly increasing bijective function, and satisfies inequality (2.28), then
where is an arbitrary constant, is an increasing bijective function, and
Proof Let
Then
and
Considering ω is nondecreasing, subadditive and submultiplicative, combining (2.46), (2.48) and Lemma 2.3, we obtain
where is a constant, and is defined in (2.45).
Let T be fixed in , and . Denote
Considering is decreasing, we have
Furthermore,
Similar to Theorem 2.1, we have
Substituting t with s in (2.52) and an integration with respect to s from t to ∞ yield
which is followed by
Combining (2.47), (2.51) and (2.53), we obtain
Setting in (2.54), yields
Since T is selected from arbitrarily, then substituting T with t, we can obtain the desired inequality (2.44). □
Next, we consider the following delay dynamic inequality on time scales:
where u, f, g, , are defined the same as in Theorem 2.1, is nondecreasing, is a constant, are constants.
Theorem 2.4 If satisfies (2.56), then
where , H are two increasing bijective functions, and
Proof Let the right side of (2.56) be . Then
and
Furthermore,
Then similar to Theorem 2.1, we have
An integration for (2.61) from t to ∞ yields
Consider is increasing, and , then (2.62) implies
Given a fixed number T in , and . Denote
Then
and furthermore,
which is followed by
Integrating (2.66) from t to ∞ yields
Consider H is increasing and , then combining (2.59), (2.65) and (2.67), we have
Setting in (2.68) and considering T is an arbitrary number in , we can obtain the desired inequality after substituting T with t. □
Finally, we study the following delay dynamic inequality on time scales:
where u, a, b, f, g, h, α, , are defined the same as in Theorem 2.1, b is defined as in Theorem 2.2, is nondecreasing, is strictly increasing.
Theorem 2.5 If for , satisfies inequality (2.69), then
where is an increasing bijective function, and
Proof Let the right side of (2.69) be . Then
and
Furthermore, considering η is increasing, we have
Fix , and let . Define
Consider a, b are decreasing on , then it follows
On the other hand,
Similar to Theorem 2.1, we have
Substituting t with s in (2.76) and an integration for (2.76) with respect to s from t to ∞ yield
Since , and is strictly increasing, then it follows
Combining (2.71), (2.75) and (2.78), we have
Setting in (2.79), we can obtain
Since is selected arbitrarily, then substituting T with t in (2.80), we can obtain the desired inequality (2.70). □
Remark 2.1 If we take for some peculiar cases in Theorems 2.3, 2.4 and 2.5 such as and , we can obtain some corollaries respectively, which are omitted here due to the limited space.
3 Some simple applications
In this section, we will present some applications for the established results above. Some new bounds for the solutions of certain delay dynamic equations on time scales will be derived in the following examples.
Example 1 Consider the delay dynamic integral equation on time scales
where , , p is a positive number with , τ is defined as in Theorem 2.1.
Theorem 3.1 Suppose is a solution of (3.1) and assume , where , then we have
where
Proof From (3.1), we obtain
Let , and . Then (3.4) can be rewritten as
A suitable application of Theorem 2.2 to (3.5) yields the desired inequality. □
Remark 3.1 In the proof of Theorem 3.1, if we apply Theorem 2.3 instead of Theorem 2.2 to (3.5), then we obtain another bound for as follows:
where is an arbitrary constant, and
Example 2 Consider the following delay dynamic differential equation on time scales:
where , , p is a positive number with , , are defined as in Theorem 2.5.
Theorem 3.2 Suppose is a solution of (3.8), and assume , , where , then we have
where G is defined as in Theorem 3.1.
Proof The equivalent integral form of (3.8) can be denoted by
Then
where , and .
A suitable application of Theorem 2.5 to (3.11) yields the desired inequality. □
4 Conclusions
In this paper, some new Gronwall-Bellman type nonlinear dynamic inequalities containing integration at infinite intervals on time scales have been established. As one can see through the present examples, the established results are useful in dealing with the boundedness of solutions of certain dynamic equations on time scales. Finally, we note that the process of Theorems 2.1-2.5 can be applied to establish delay dynamic inequalities with two independent variables on time scales.
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Acknowledgements
This work is partially supported by National Natural Science Foundation of China (Grant No. 11171178).
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QF carried out the main part of this article. All authors read and approved the final manuscript.
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Zheng, B., Feng, Q., Meng, F. et al. Some new Gronwall-Bellman type nonlinear dynamic inequalities containing integration on infinite intervals on time scales. J Inequal Appl 2012, 201 (2012). https://doi.org/10.1186/1029-242X-2012-201
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DOI: https://doi.org/10.1186/1029-242X-2012-201