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Converses of nabla Pachpatte-type dynamic inequalities on arbitrary time scales

  • Zeynep Kayar EMAIL logo and Billur Kaymakçalan
Published/Copyright: March 25, 2025
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Abstract

Reverse Pachpatte-type inequalities are concave generalizations of the well-known Bennett-Leindler-type inequalities. We establish reverse nabla Pachpatte-type dynamic inequalities taking account of concavity. It is the first time that converses of Pachpatte-type inequalities are obtained in the nabla time scale calculus as well as for its special cases such as continuous and discrete cases and for the dual results obtained in the delta time scale calculus. Moreover, some of our results extend the related ones when concavity has been removed.

MSC 2010: 34N05; 26D10; 26D15; 26A51

1 Introduction

Our aim is to obtain converses of Pachpatte-type dynamic inequalities in the nabla time scale calculus, which are concave generalizations of nabla Bennett-Leindler-type dynamic inequalities.

Since Bennett-Leindler-type inequalities turn information about derivatives of functions into information about the size of the function, they are essential part of all areas of mathematics and useful in various applications, see [14].

The Bennett-Leindler inequality has appeared as being converse of celebrated Hardy’s inequality.

Hardy [5] obtained the following discrete inequality for a sequence u ( k ) 0 and for a constant δ > 1 as

(1) = 1 1 j = 1 u ( j ) δ δ δ 1 δ = 1 u δ ( ) ,

and then Hardy et al. [6, Theorem 330] derived continuous version of inequality (1) as

(2) 0 X δ ( t ) t ξ d t δ ξ 1 δ 0 x δ ( t ) t ξ δ d t , if ξ > 1 and X ( t ) = 0 t x ( s ) d s δ 1 ξ δ 0 x δ ( t ) t ξ δ d t , if ξ < 1 and X ( t ) = t x ( s ) d s ,

where x ( t ) 0 , δ > 1 .

Although a great deal of attention has been paid to Hardy’s inequalities to improve, generalize, and prove them in different ways and there are numerous research papers and also some books, we restrict ourselves to focus on the direction of Copson [7, Theorems 1.1, 2.1] and [8, Theorems 1, 3] for the generalization. In this direction, we refer the books [1,2,6,9,10] and the articles [7,1116] and [8,1720].

The convex extensions of Hardy-Copson-type inequalities have showed up in the literature after the celebrated papers of Pachpatte. Pachpatte [21] and Hwang and Yang [22] generalized the discrete Hardy-Copson inequalities as

(3) = 1 g ( ) C δ H ( ) G ¯ ( ) δ δ 1 δ = 1 g ( ) C δ ( h ( ) ) , δ > 1 ,

where C ( z ) is a real-valued positive convex function defined for z > 0 and g ( k ) , h ( k ) are nonnegative sequences and G ¯ ( ) = j = 1 g ( j ) and H ( ) = j = 1 g ( j ) h ( j ) . If C ( z ) = z and g ( ) 1 , 1 , then inequality (3) implies Hardy’s discrete inequality (1).

Then, continuous version of discrete Pachpatte’s inequality (3) was derived in 1990 by Pachpatte [23] as follows: If C ( z ) is a real-valued nonnegative convex function defined for z > 0 , the functions x ( t ) > 0 , v ( t ) 0 are real-valued and integrable and δ 1 , ξ > 1 are constants, then

(4) 0 x ( t ) X ¯ ξ δ ( t ) C δ V ( t ) X ¯ ( t ) d t δ ξ 1 δ 0 x ( t ) C δ ( v ( t ) ) X ξ δ ( t ) d t ,

where X ¯ ( t ) = 0 t x ( s ) d s and V ( t ) = 0 t x ( s ) v ( s ) d s . If C ( z ) = z and x ( t ) 1 , t 0 , then inequality (4) implies Hardy’s continuous inequality (2).

The following inequality was established by Pachpatte [24] in 1994, which is another continuous variant of his discrete inequality (3). If δ 1 , κ 0 are constants, then

(5) 0 x ( t ) C δ + κ V ( t ) X ¯ ( t ) d t δ + κ δ + κ 1 δ 0 x ( t ) C δ ( v ( t ) ) Y ( t ) X ¯ ( t ) κ d t ,

where the functions x , v , C , X ¯ , and V are defined as in inequality (4) and Y ( t ) = 0 t x ( s ) C ( v ( s ) ) d s . If C ( z ) = z , κ = 0 and x ( t ) 1 , t 0 , then inequality (5) implies continuous version of Hardy’s discrete inequality (1).

After that Pečarić and Hanjš [25] made a combination of inequalities (4) and (5) as

(6) 0 x ( s ) X ¯ ξ δ ( t ) C δ + κ V ( t ) X ¯ ( t ) d t δ + κ ξ + κ 1 δ 0 x ( t ) Y κ ( t ) X ¯ κ + ξ δ ( t ) C δ ( v ( t ) ) d t ,

where the functions x , v , X ¯ , V , Y , C and the constants δ , κ are defined as in inequality (5) and ξ > 1 . The special cases of inequality (6), which are inequalities (4) and (5), can be obtained by choosing κ = 0 and ξ = δ in inequality (6), respectively.

The Bennett-Leindler inequality, which is a converse of the Hardy-Copson inequality, first appeared in the literature when Hardy and Littlewood [26] obtained its discrete version in 1927. The most generalized discrete Bennett-Leindler inequalities were derived by Copson [7], Bennett [27], and Leindler [12] for nonnegative sequences g and h and for 0 < δ < 1 , as follows:

= 1 g ( ) [ G ¯ ( ) ] ξ j = h ( j ) g ( j ) δ δ δ = 1 g ( ) h δ ( ) [ G ¯ ( ) ] ξ δ , 0 ξ < 1 ,

where G ¯ is defined as in inequality (3) and

(7) = 1 g ( ) [ G ¯ ( ) ] ξ j = h ( j ) g ( j ) δ δ 1 ξ δ = 1 g ( ) h δ ( ) [ G ¯ ( ) ] ξ δ , ξ < 0

and for 0 < L g ( ) g ( + 1 ) ,

(8) = 1 g ( ) [ G ¯ ( ) ] ξ j = 1 h ( j ) g ( j ) δ L δ ξ 1 δ = 1 g ( ) h δ ( ) [ G ¯ ( ) ] ξ δ , ξ > 1 .

As far as we know, Hardy et al. [6, Theorem 337] established the first reverse version of the continuous Hardy-Copson inequality (2) for ξ = δ , which is the original continuous Bennett-Leindler inequality, as

0 X ¯ δ ( t ) t δ d t δ 1 δ δ 0 x δ ( t ) d t , x ( t ) 0 ,

where X ¯ are defined as in inequality (4) and 0 < δ < 1 .

Below is the last continuous Bennett-Leindler inequalities, which are continuous counterparts of the discrete Bennett-Leindler inequalities (7) and (8), obtained by Copson in [8, Theorems 4, 2], respectively,

0 b x ( t ) [ X ¯ ( t ) ] ξ [ V ¯ ( t ) ] δ d t δ 1 ξ δ 0 b x ( t ) [ X ¯ ( t ) ] δ ξ v δ ( t ) d t , 0 < δ 1 , ξ < 1 , 0 < b ,

and

a x ( t ) [ X ¯ ( t ) ] ξ [ V ( t ) ] δ d t δ ξ 1 δ a x ( t ) [ X ¯ ( t ) ] δ ξ v δ ( t ) d t , 0 < δ 1 < ξ , a > 0 ,

where the functions x , v , X ¯ , V are defined as in inequality (4) and V ¯ ( t ) = t x ( s ) v ( s ) d s .

Several renowned inequalities have been developed in arbitrary time scales both in the delta time scale calculus [2830] and in the nabla case [3137] owing to the discovery of the calculus on a time scale [3842].

Dynamic Hardy-Copson-type inequalities have been initially obtained by the delta approach. These unifications are presented in the book [43] and in the articles [4452]. Their nabla analogues are given in [5355].

The reverse delta Hardy-Copson-type inequalities, named delta Bennett-Leindler inequalities, are shown in [49,5658] for 0 < δ < 1 . These outcomes emerge as a result of unifications of discrete and continuous Bennett-Leindler inequalities, which were mentioned above. Besides delta calculus, the discrete and continuous Bennett-Leindler inequalities can be unified in nabla time scale calculus and the foregoing reverse Hardy-Copson-type inequalities can be generated for the nabla case [36,37]. These inequalities are named nabla Bennett-Leindler inequalities.

Some Pachpatte-type dynamic inequalities, which are convex generalizations of Hardy-Copson-type dynamic inequalities, were obtained in [48,59,60] via delta time scale calculus whereas their nabla counterparts can be found in [61,62].

Although dynamic Hardy-Copson-type inequalities were generalized via convexity in the time scale calculus by using delta and nabla approaches, their converse inequalities, which are named Bennett-Leindler dynamic inequalities, have not been considered so far. Therefore, our aim is to establish concave generalizations of the aforementioned Bennett-Leindler-type dynamic inequalities and to establish converses of nabla Pachpatte-type inequalities, which do not exist in the literature. We derive novel results for the nabla case as well as for the delta, continuous and discrete cases.

2 Preliminaries

This section is devoted to present the main definitions and theorems of the nabla time scale calculus. The fundamental theories of the delta and nabla calculi can be found in the books [38,39] or in the articles [4042,48,54].

If T is a closed subset of R , then T is called a time scale. If t > inf T , we define the backward jump operator ρ : T T by ρ ( t ) sup { τ < t : τ T } . The backward graininess function ν : T R 0 + is defined by ν ( t ) t ρ ( t ) , for t T .

The -derivative of f : T R at the point t T κ = T [ inf T , σ ( inf T ) ) denoted by f ( t ) is the number enjoying the property that for all ε > 0 , there exists a neighborhood V T of t T κ such that

f ( s ) f ( ρ ( t ) ) f ( t ) ( s ρ ( t ) ) ε s ρ ( t )

for all s V .

The nabla derivative satisfies the following.

Lemma 2.1

 [38,41] Let f : T R and t T κ .

  1. If f is continuous at a left scattered point t, then f is nabla differentiable at t with f ( t ) = f ( t ) f ( ρ ( t ) ) ν ( t ) .

  2. f is nabla differentiable at a left dense point t if and only if the limit f ( t ) = lim s t f ( t ) f ( s ) t s exists as a finite number.

  3. If f is nabla differentiable at t, then f ρ ( t ) = f ( t ) ν ( t ) f ( t ) .

A function f : T R is ld-continuous if it is continuous at each left-dense points in T and lim s t + f ( s ) exists as a finite number for all right-dense points in T . The set C l d ( T , R ) denotes the class of real, ld-continuous functions defined on a time scale T .

If f C l d ( T , R ) , then there exists a function f ¯ ( t ) such that f ¯ ( t ) = f ( t ) and the nabla integral of f is defined by a b f ( s ) s = f ¯ ( b ) f ¯ ( a ) .

Some of the properties of the nabla integral are gathered next.

Lemma 2.2

 [38,41] Let t 1 , t 2 , t 3 T with t 1 < t 3 < t 2 and a , b R . If Λ , Γ : T R are ld-continuous, then

  1. t 1 t 2 [ a Λ ( s ) + b Γ ( s ) ] s = a t 1 t 2 Λ ( s ) ( s ) + b t 1 t 2 Γ ( s ) s .

  2. t 1 t 1 Λ ( s ) ( s ) = 0 .

  3. t 1 t 3 Λ ( s ) s + t 3 t 2 Λ ( s ) s = t 1 t 2 Λ ( s ) s = t 2 t 1 Λ ( s ) s .

  4. Integration by parts formula holds:

    t 1 t 2 Λ ( s ) Γ ( s ) s = Λ ( t 2 ) Γ ( t 2 ) Λ ( t 1 ) Γ ( t 1 ) t 1 t 2 Λ ( s ) Γ ( ρ ( s ) ) s .

Lemma 2.3

(Chain rule for the nabla derivative)  [33] If Λ : R R is continuously differentiable and Γ : T R is nabla differentiable, then Λ Γ is nabla differentiable and

( Λ Γ ) ( s ) = Γ ( s ) 0 1 Λ ( Γ ( ρ ( s ) ) + h ν ( s ) Γ ( s ) ) d h .

Lemma 2.4

(Hölder’s inequality) [32] For s 1 , s 2 T , if f , g C l d ( [ s 1 , s 2 ] T , R ) and α , β > 1 are constants with 1 α + 1 β = 1 , then nabla Hölder’s inequality

s 1 s 2 f ( s ) g ( s ) s s 1 s 2 f ( s ) α s 1 α s 1 s 2 f ( s ) β s 1 β h o l d s t r u e .

When 0 < α < 1 or α < 0 with 1 α + 1 β = 1 , the reverse nabla Hölder’s inequality

(9) s 1 s 2 f ( s ) g ( s ) s s 1 s 2 f ( s ) α s 1 α s 1 s 2 g ( s ) β s 1 β

is satisfied.

The reverse nabla Jensen’s inequality is a main tool in our results.

Lemma 2.5

(Jensen’s inequality) [32,63] For s 1 , s 2 T and s 3 , s 4 R , if f C l d ( [ s 1 , s 2 ] , [ s 3 , s 4 ] ) and g C l d ( [ s 1 , s 2 ] , R ) satisfying s 1 s 2 g ( s ) s > 0 with a convex function C C ( ( s 3 , s 4 ) , R ) , then

C s 1 s 2 g ( s ) f ( s ) s s 1 s 2 g ( s ) s s 1 s 2 g ( s ) C ( f ( s ) ) s s 1 s 2 g ( s ) s

holds.

If C C ( ( s 3 , s 4 ) , R ) is concave, then the inequality sign is replaced by , that is, the reverse nabla Jensen’s inequality

(10) C s 1 s 2 g ( s ) f ( s ) s s 1 s 2 g ( s ) s s 1 s 2 g ( s ) C ( f ( s ) ) s s 1 s 2 g ( s ) s

holds.

3 Converses of Pachpatte-type inequalities

The following auxiliary functions will play central roles in our results:

(11) X ( t ) = t x ( s ) s , V ( t ) = c t x ( s ) v ( s ) s , Y ( t ) = c t x ( s ) C ( v ( s ) ) s , X ¯ ( t ) = c t x ( s ) s , V ¯ ( t ) = t x ( s ) v ( s ) s , Y ¯ ( t ) = t x ( s ) C ( v ( s ) ) s ,

where x , v 0 are left dense continuous, nabla differentiable and locally nabla integrable functions, C : [ 0 , ) [ 0 , ) is a concave function and 0 < c T .

Since converses of Pachpatte-type dynamic inequalities are concave generalizations of nabla Bennett-Leindler-type dynamic inequalities, in the proofs of the theorems we first employ concavity and subsequently prove Bennett-Leindler-type dynamic inequalities.

Theorem 3.1

For the functions X , V , and Y defined as in (11), let D 1 X ( t ) X ρ ( t ) , t ( c , ) T be fulfilled for some D 1 > 0 . If 0 < δ < 1 , κ 0 and 0 κ + ξ < 1 are real numbers, then for a nonnegative concave function C and

  1. for 0 < κ + δ 1 , one can obtain

    1. (12) c x ( t ) C κ + δ ( V ( t ) ) [ X ( t ) ] κ + ξ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) Y κ ( t ) [ X ( t ) ] κ + ξ δ t ,

    2. (13) c x ( t ) C κ + δ ( V ( t ) ) [ X ρ ( t ) ] κ + ξ t D 1 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) Y κ ( t ) [ X ρ ( t ) ] κ + ξ δ t ,

  2. for κ + δ 1 , one can obtain

    1. (14) c x ( t ) C κ + δ ( V ρ ( t ) ) [ X ( t ) ] κ + ξ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ρ ( t ) ] κ [ X ( t ) ] κ + ξ δ t ,

    2. (15) c x ( t ) C κ + δ ( Y ρ ( t ) ) [ X ρ ( t ) ] κ + ξ t D 1 ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ρ ( t ) ] κ [ X ρ ( t ) ] κ + ξ δ t .

Proof

We first prove (I). Concavity of the function C implies the reverse Jensen’s inequality (10) that

(16) C ( V ( t ) ) = C c t x ( s ) v ( s ) s c t x ( s ) C ( v ( s ) ) s = Y ( t ) .

(I)–(i) After taking account of inequality (16), estimation of the left-hand side of inequality (12) implies

(17) c x ( t ) C κ + δ ( Y ( t ) ) [ X ( t ) ] κ + ξ t c x ( t ) [ Y ( t ) ] κ + δ [ X ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (17) and obtain

c x ( t ) [ Y ( t ) ] κ + δ [ X ( t ) ] κ + ξ t = u ( t ) Y ( t ) c c u ρ ( t ) [ Y κ + δ ( t ) ] t ,

where u ( t ) = t x ( s ) [ X ( s ) ] κ + ξ s . Using Y ( c ) = 0 and u ( ) = 0 yields

(18) c x ( t ) [ Y ( t ) ] κ + δ [ X ( t ) ] κ + ξ t = c u ρ ( t ) [ Y κ + δ ( t ) ] t .

For Y ( t ) = x ( t ) C ( v ( t ) ) 0 , using the chain rule for the nabla derivative provides

(19) [ Y κ + δ ( t ) ] = 0 1 ( κ + δ ) Y ( t ) d h [ h Y ( t ) + ( 1 h ) Y ρ ( t ) ] 1 κ δ ( κ + δ ) x ( t ) Y ( v ( t ) ) [ Y ( t ) ] κ + δ 1 ,

where we have used Y ( t ) 0 and Y ρ ( t ) Y ( t ) for 0 < κ + δ 1 and for all t [ c , ) T .

Moreover, for X ( t ) = x ( t ) 0 , using the chain rule for the nabla derivative provides

(20) [ X 1 κ ξ ( t ) ] = 0 1 ( 1 κ ξ ) X ( t ) d h [ h X ( t ) + ( 1 h ) X ρ ( t ) ] κ + ξ ( 1 κ ξ ) x ( t ) [ X ( t ) ] κ + ξ ( 1 κ ξ ) x ( t ) [ X ρ ( t ) ] κ + ξ D 1 κ + ξ ,

where we have used X ( t ) 0 and X ρ ( t ) X ( t ) for 0 κ + ξ < 1 and for all t [ c , ) T .

Inequality (20) implies that

(21) x ( t ) [ X ( t ) ] κ + ξ [ X 1 κ ξ ( t ) ] 1 κ ξ

and

(22) x ( t ) [ X ρ ( t ) ] κ + ξ D 1 κ + ξ [ X 1 κ ξ ( t ) ] 1 κ ξ .

Then, one can obtain from inequality (21) that

u ρ ( t ) = ρ ( t ) x ( s ) [ X ( s ) ] κ + ξ s ρ ( t ) [ X 1 κ ξ ( s ) ] 1 κ ξ s = [ X ρ ( t ) ] 1 κ ξ 1 κ ξ [ X ( t ) ] 1 κ ξ 1 κ ξ .

Then, inequality (18) reduces to

c x ( t ) [ Y ( t ) ] κ + δ [ X ( t ) ] κ + ξ t κ + δ 1 κ ξ c x ( t ) C ( x ( t ) ) [ Y ( t ) ] κ + δ 1 [ X ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies

c x ( t ) [ Y ( t ) ] κ + δ [ X ( t ) ] κ + ξ t 1 δ κ + δ 1 κ ξ c x ( t ) C δ ( x ( t ) ) [ Y ( t ) ] κ [ X ( t ) ] κ + ξ δ t 1 δ .

Taking δ -th power of the both sides of the above inequality yields inequality (12) after taking into account inequality (17).

(I)–(ii) After taking account of inequality (16), estimation of the left-hand side of inequality (13) implies

(23) c x ( t ) C κ + δ ( Y ( t ) ) [ X ρ ( t ) ] κ + ξ t c x ( t ) [ Y ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (23) and obtain

c x ( t ) [ Y ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t = u ( t ) Y ( t ) c c u ρ ( t ) [ Y κ + δ ( t ) ] t ,

where u ( t ) = t x ( s ) [ X ρ ( s ) ] κ + ξ s . Using Y ( c ) = 0 and u ( ) = 0 yields

(24) c x ( t ) [ Y ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t = c u ρ ( t ) [ Y κ + δ ( t ) ] t .

Then, one can obtain from inequality (22) that

u ρ ( t ) = ρ ( t ) x ( s ) [ X ρ ( s ) ] κ + ξ s D 1 κ + ξ 1 κ ξ ρ ( t ) [ X 1 κ ξ ( s ) ] s = D 1 κ + ξ [ X ρ ( t ) ] 1 κ ξ 1 κ ξ .

Then, substituting the above inequality and inequality (19) to inequality (24) provides

c x ( t ) [ Y ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t D 1 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ( t ) ] κ + δ 1 [ X ρ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (13) after taking into account inequality (23).

Now, we prove (II). Concavity of the function C implies the reverse Jensen’s inequality (10) that

(25) C ( V ρ ( t ) ) = C c ρ ( t ) x ( s ) v ( s ) s c ρ ( t ) x ( s ) C ( v ( s ) ) s = Y ρ ( t ) .

(II)–(i) After taking account of inequality (25), estimation of the left-hand side of inequality (14) implies

(26) c x ( t ) C κ + δ ( Y ρ ( t ) ) [ X ( t ) ] κ + ξ t c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (26) and obtain

c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t = u ( t ) Y ( t ) c c u ( t ) [ Y κ + δ ( t ) ] t ,

where u ( t ) = t x ( s ) [ X ( s ) ] κ + ξ s . Using Y ( c ) = 0 and u ( ) = 0 yields

(27) c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t = c u ( t ) [ Y κ + δ ( t ) ] t .

For Y ( t ) = x ( t ) C ( v ( t ) ) 0 , using the chain rule for the nabla derivative provides

(28) [ Y κ + δ ( t ) ] = 0 1 ( κ + δ ) Y ( t ) d h [ h Y ( t ) + ( 1 h ) Y ρ ( t ) ] 1 κ δ ( κ + δ ) x ( t ) C ( v ( t ) ) [ Y ρ ( t ) ] κ + δ 1 ,

where we have used Y ( t ) 0 and Y ρ ( t ) Y ( t ) for κ + δ 1 and for all t [ c , ) T .

Then, one can obtain from inequality (21) that

u ( t ) = t x ( s ) [ X ( s ) ] κ + ξ s t [ X 1 κ ξ ( s ) ] ( 1 κ ξ ) s = [ X ( t ) ] 1 κ ξ 1 κ ξ .

Then, inequality (27) reduces to

c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t κ + δ 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ρ ( t ) ] κ + δ 1 [ X ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (14) after taking into account inequality (26).

(II)–(ii) After taking account of inequality (25), estimation of the left-hand side of inequality (15) implies

(29) c x ( t ) C κ + δ ( V ρ ( t ) ) [ X ρ ( t ) ] κ + ξ t c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (29) and obtain

c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t = u ( t ) Y ( t ) c c u ( t ) [ Y κ + δ ( t ) ] t ,

where u ( t ) = t x ( s ) [ X ρ ( s ) ] κ + ξ s . Using Y ( c ) = 0 and u ( ) = 0 yields

(30) c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t = c u ( t ) [ Y κ + δ ( t ) ] t .

Then, one can obtain from inequality (22) that

u ( t ) = t x ( s ) [ X ρ ( s ) ] κ + ξ s D 1 κ + ξ 1 κ ξ t [ X 1 κ ξ ( s ) ] s = D 1 κ + ξ [ X ( t ) ] 1 κ ξ 1 κ ξ .

Then, substituting the above inequality and inequality (28) to inequality (30) provides

c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t D 1 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ρ ( t ) ] κ + δ 1 [ X ( t ) ] κ + ξ 1 t D 1 ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ρ ( t ) ] κ + δ 1 [ X ρ ( t ) ] κ + ξ 1 t ,

where D 1 X ( t ) X ρ ( t ) , t ( c , ) T . The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (15) after taking into account inequality (29).□

Remark 3.2

When C ( z ) = z , inequalities (12)–(15) reduce to novel nabla Bennett-Leindler-type inequalities established if 0 < δ < 1 , κ 0 and 0 κ + ξ < 1 . Therefore, inequalities (12)–(15) are concave extensions of the nabla Bennett-Leindler-type inequalities. Moreover, they are converses of the nabla Pachpatte-type inequalities shown in (ii) of [61, Theorem 4] and (i) of [64, Remark 2].

Corollary 3.3

Delta versions of the nabla inequalities (12)–(15) can be derived for the following functions:

(31) X ( t ) = t x ( s ) Δ s , V ( t ) = c t x ( s ) v ( s ) Δ s , Y ( t ) = c t x ( s ) C ( v ( s ) ) Δ s , X ¯ ( t ) = c t x ( s ) Δ s , V ¯ ( t ) = t x ( s ) v ( s ) Δ s , Y ¯ ( t ) = t x ( s ) C ( v ( s ) ) Δ s .

Let E 1 X σ ( t ) X ( t ) , t ( c , ) T be fulfilled for some E 1 > 0 and 0 < δ < 1 , κ 0 and 0 κ + ξ < 1 be real constants.

Then, nabla inequalities (12)–(15) turn into new delta inequalities. For a concave function C and for the functions X, V, and Y defined as in (31) and

  1. for 0 < κ + δ 1 , one can obtain

    1. (32) c x ( t ) C κ + δ ( V σ ( t ) ) [ X σ ( t ) ] κ + ξ Δ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y σ ( t ) ] κ [ X σ ( t ) ] κ + ξ δ Δ t ,

    2. (33) c x ( t ) C κ + δ ( V σ ( t ) ) [ X ( t ) ] κ + ξ Δ t E 1 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y σ ( t ) ] κ [ X ( t ) ] κ + ξ δ Δ t ,

  2. for κ + δ 1 , one can obtain

    1. (34) c x ( t ) C κ + δ ( V ( t ) ) [ X σ ( t ) ] κ + ξ Δ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ( t ) ] κ [ X σ ( t ) ] κ + ξ δ Δ t ,

    2. (35) c x ( t ) C κ + δ ( V ( t ) ) [ X ( t ) ] κ + ξ Δ t E 1 ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ( t ) ] κ [ X ( t ) ] κ + ξ δ Δ t .

When C ( z ) = z , inequalities (32)–(35) reduce to novel delta Bennett-Leindler-type inequalities established if 0 < δ < 1 , κ 0 and 0 κ + ξ < 1 . Therefore, inequalities (32)–(35) are concave extensions of the delta Bennett-Leindler-type inequalities. Moreover, they are converses of the delta Pachpatte-type inequalities shown in (ii) of [61, Corollary 4].

Theorem 3.4

For the functions X , V , and Y defined in (11), let X ρ ( t ) X ( t ) D 2 , t ( c , ) T be fulfilled for some D 2 > 0 . If 0 < δ < 1 , κ 0 and κ + ξ 0 are real numbers, then for a nonnegative concave function C and

  1. for 0 < κ + δ 1 , we have

    1. (36) c x ( t ) C κ + δ ( V ( t ) ) [ X ( t ) ] κ + ξ t D 2 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) Y κ ( t ) [ X ( t ) ] κ + ξ δ t ,

    2. (37) c x ( t ) C κ + δ ( V ( t ) ) [ X ρ ( t ) ] κ + ξ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) Y κ ( t ) [ X ρ ( t ) ] κ + ξ δ t ,

  2. for κ + δ 1 , we have

    1. (38) c x ( t ) C κ + δ ( V ρ ( t ) ) [ X ( t ) ] κ + ξ t D 2 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ρ ( t ) ] κ [ X ( t ) ] κ + ξ δ t ,

    2. (39) c x ( t ) C κ + δ ( V ρ ( t ) ) [ X ρ ( t ) ] κ + ξ t D 2 κ + ξ 1 ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ρ ( t ) ] κ [ X ρ ( t ) ] κ + ξ δ t .

Proof

Using the same structure as suggested in the proof of Theorem 3.1 leads to the proof.

(I)–(i) After employing concavity of the function C and applying the similar ideas in the proof of (I)–(i) of Theorem 3.1, we reach inequality (18).

For X ( t ) = x ( t ) 0 , using the chain rule for the nabla derivative provides

(40) [ X 1 κ ξ ( t ) ] = 0 1 ( 1 κ ξ ) X ( t ) d h [ h X ( t ) + ( 1 h ) X ρ ( t ) ] κ + ξ ( 1 κ ξ ) x ( t ) [ X ρ ( t ) ] κ + ξ ( 1 κ ξ ) x ( t ) [ X ( t ) ] κ + ξ D 2 κ + ξ ,

where we have used X ( t ) 0 and X ρ ( t ) X ( t ) for κ + ξ 0 and for all t [ c , ) T .

Inequality (40) implies that

(41) x ( t ) [ X ρ ( t ) ] κ + ξ [ X 1 κ ξ ( t ) ] 1 κ ξ

and

(42) x ( t ) [ X ( t ) ] κ + ξ D 2 κ + ξ [ X 1 κ ξ ( t ) ] 1 κ ξ .

By applying the similar ideas of the proof of Theorem 3.1 for the functions X and Y , the following is observed.

c x ( t ) [ Y ( t ) ] κ + δ [ X ( t ) ] κ + ξ t D 2 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ( t ) ] κ + δ 1 [ X ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (36).

(I)–(ii) After employing concavity of the function C and applying the similar ideas in the proof of (I)-(ii) of Theorem 3.1, we reach inequality (24).

Then, estimating the function u ρ by using inequality (42) and substituting the resulting inequality and inequality (19) to the inequality (24), we obtain

c x ( t ) [ Y ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t D 2 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ( t ) ] κ + δ 1 [ X ρ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (37).

(II)-(i) After employing concavity of the function C and applying the similar ideas in the proof of (II)–(i) of Theorem 3.1, we reach inequality (27).

Then, estimating the function u by using inequality (42) and substituting the resulting inequality and inequality (28) to the inequality (27), we obtain

c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t D 2 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ρ ( t ) ] κ + δ 1 [ X ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (38).

(II)–(ii) After employing concavity of the function C and applying the similar ideas in the proof of (II)-(ii) of Theorem 3.1, we reach inequality (30).

Then, estimating the function u by using inequality (41) and substituting the resulting inequality and inequality (28) to the inequality (30), we obtain

c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t D 2 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ρ ( t ) ] κ + δ 1 [ X ρ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (39).□

Remark 3.5

When C ( z ) = z , inequalities (36)–(39) reduce to novel nabla Bennett-Leindler-type inequalities established if 0 < δ < 1 , κ 0 , and κ + ξ 0 . Therefore, inequalities (36)–(39) are concave extensions of the nabla Bennett-Leindler-type inequalities. Moreover, they are converses of the nabla Pachpatte-type inequalities shown in (i) of [61, Theorem 4] and (ii) of [64, Remark 2].

When C ( z ) = z , inequality (37) is a generalization of inequality (3.1) in [36, Theorem 3.1]. In addition to C ( z ) = z , if κ = 0 in inequality (37), then inequality (37) coincides inequality (3.1) in [36, Theorem 3.1].

Corollary 3.6

Let X ( t ) X σ ( t ) E 2 , t ( c , ) T be fulfilled for some E 2 > 0 and for X , X σ defined as in (31). Let 0 < δ < 1 , κ 0 and κ + ξ 0 be real constants.

Then, nabla inequalities (36)–(39) turn into new delta inequalities. For a concave function C and for the functions X , V , and Y defined as in (31) and

  1. for 0 < κ + δ 1 , one can obtain

    1. (43) c x ( t ) C κ + δ ( V σ ( t ) ) [ X σ ( t ) ] κ + ξ Δ t E 2 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y σ ( t ) ] κ [ X σ ( t ) ] κ + ξ δ Δ t ,

    2. (44) c x ( t ) C κ + δ ( V σ ( t ) ) [ X ( t ) ] κ + ξ Δ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y σ ( t ) ] κ [ X ( t ) ] κ + ξ δ Δ t ,

  2. for κ + δ 1 , one can obtain

    1. (45) c x ( t ) C κ + δ ( V ( t ) ) [ X σ ( t ) ] κ + ξ Δ t E 2 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ( t ) ] κ [ X σ ( t ) ] κ + ξ δ Δ t ,

    2. (46) c x ( t ) C κ + δ ( V ( t ) ) [ X ( t ) ] κ + ξ Δ t E 2 κ + ξ 1 ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ( t ) ] κ [ X ( t ) ] κ + ξ δ Δ t .

When C ( z ) = z , inequalities (43)–(46) reduce to novel delta Bennett-Leindler-type inequalities established if 0 < δ < 1 , κ 0 , and κ + ξ 0 . Therefore, inequalities (43)–(46) are concave extensions of the delta Bennett-Leindler-type inequalities. Moreover, they are converses of the delta Pachpatte-type inequalities shown in (i) of [61, Corollary 4].

When C ( z ) = z , inequality (44) is a generalization of inequality (2.5) in [58, Theorem 2.1]. In addition to C ( z ) = z , if κ = 0 in inequality (44), then inequality (44) coincides inequality (2.5) in [58, Theorem 2.1].

Theorem 3.7

For the functions X ¯ , V ¯ , and Y ¯ defined as in (11), let D 3 X ¯ ρ ( t ) X ¯ ( t ) , t ( c , ) T be fulfilled for some D 3 > 0 . If 0 < δ < 1 , κ 0 and 0 κ + ξ < 1 are real numbers, then for a nonnegative concave function C and

  1. for 0 < κ + δ 1 , we obtain

    1. (47) c x ( t ) C κ + δ ( V ¯ ρ ( t ) ) [ X ¯ ( t ) ] κ + ξ t D 3 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ t ,

    2. (48) c x ( t ) C κ + δ ( V ¯ ρ ( t ) ) [ X ¯ ρ ( t ) ] κ + ξ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ [ X ¯ ρ ( t ) ] κ + ξ δ t ,

  2. for κ + δ 1 , we obtain

    1. (49) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ¯ ( t ) ] κ + ξ t D 3 ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ t ,

    2. (50) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ¯ ρ ( t ) ] κ + ξ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ¯ ρ ( t ) ] κ + ξ δ t .

Proof

We first prove (I). Concavity of the function C implies the reverse Jensen’s inequality (10) that

(51) C ( V ¯ ρ ( t ) ) = C ρ ( t ) x ( s ) v ( s ) s ρ ( t ) x ( s ) C ( v ( s ) ) s = Y ¯ ρ ( t ) .

(I)–(i): After taking account of inequality (51), estimation of the left-hand side of inequality (47) implies

(52) c x ( t ) C κ + δ ( V ¯ ρ ( t ) ) [ X ¯ ( t ) ] κ + ξ t c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (52) and obtain

c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t = u ( t ) Y ¯ ( t ) c c u ( t ) [ Y ¯ κ + δ ( t ) ] t ,

where u ( t ) = c t x ( s ) [ X ¯ ( s ) ] κ + ξ s . Using Y ¯ ( ) = 0 and u ( c ) = 0 yields

(53) c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t = c u ( t ) [ Y ¯ κ + δ ( t ) ] t .

For Y ¯ ( t ) = x ( t ) C ( v ( t ) ) 0 , using the chain rule for the nabla derivative provides

(54) [ Y ¯ κ + δ ( t ) ] = 0 1 ( κ + δ ) Y ¯ ( t ) d h [ h Y ¯ ( t ) + ( 1 h ) Y ¯ ρ ( t ) ] 1 κ δ ( κ + δ ) x ( t ) C ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ + δ 1 ,

where we have used Y ¯ ( t ) 0 and Y ¯ ρ ( t ) Y ¯ ( t ) for 0 < κ + δ 1 and for all t [ c , ) T .

Moreover, for X ¯ ( t ) = x ( t ) 0 , using the chain rule for the nabla derivative provides

(55) [ X ¯ 1 κ ξ ( t ) ] = 0 1 ( 1 κ ξ ) X ( t ) d h [ h X ¯ ( t ) + ( 1 h ) X ¯ ρ ( t ) ] κ + ξ ( 1 κ ξ ) x ( t ) [ X ¯ ρ ( t ) ] κ + ξ ( 1 κ ξ ) p ( t ) [ X ¯ ( t ) ] κ + ξ D 3 κ + ξ ,

where X ¯ ( t ) 0 and X ¯ ρ ( t ) X ¯ ( t ) have been used for 0 κ + ξ < 1 and for all t [ c , ) T .

Inequality (55) implies that

(56) x ( t ) [ X ¯ ( t ) ] κ + ξ D 3 κ + ξ [ X ¯ 1 κ ξ ( t ) ] 1 κ ξ

and

(57) x ( t ) [ X ¯ ρ ( t ) ] κ + ξ [ X ¯ 1 κ ξ ( t ) ] 1 κ ξ .

Then, one can obtain from inequality (56) that

(58) u ( t ) = c t x ( s ) [ X ¯ ( s ) ] κ + ξ s D 3 κ + ξ c t [ X ¯ 1 κ ξ ( s ) ] ( 1 κ ξ ) s = D 3 κ + ξ [ X ¯ ( t ) ] 1 κ ξ 1 κ ξ .

Then, inequality (53) reduces to

c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t D 3 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ + δ 1 [ X ¯ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies

c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t 1 δ D 3 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ t 1 δ .

Taking δ -th power of the both sides of the above inequality yields inequality (47) after taking into account inequality (52).

(I)–(ii): After taking account of inequality (51), estimation of the left-hand side of inequality (48) implies

(59) c x ( t ) C κ + δ ( V ¯ ρ ( t ) ) [ X ¯ ρ ( t ) ] κ + ξ t c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (59) and obtain

c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t = u ( t ) Y ¯ ( t ) c c u ( t ) [ Y ¯ κ + δ ( t ) ] t ,

where u ( t ) = c t x ( s ) [ X ¯ ρ ( s ) ] κ + ξ s . Using Y ¯ ( ) = 0 and u ( c ) = 0 yields

(60) c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t = c u ( t ) [ Y ¯ κ + δ ( t ) ] t .

Then, one can obtain from inequality (57) that

u ( t ) = c t x ( s ) [ X ¯ ρ ( s ) ] κ + ξ s c t [ X ¯ 1 κ ξ ( s ) ] 1 κ ξ s = [ X ¯ ( t ) ] 1 κ ξ 1 κ ξ [ X ¯ ρ ( t ) ] 1 κ ξ 1 κ ξ .

Then, substituting the above inequality and inequality (54) to inequality (60) provides

c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t κ + δ 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ + δ 1 [ X ¯ ρ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (48) after taking into account inequality (59).

Now, we prove (II). Concavity of the function C implies the reverse Jensen’s inequality (10) that

(61) C ( V ¯ ( t ) ) = C t x ( s ) v ( s ) s t x ( s ) C ( v ( s ) ) s = Y ¯ ( t ) .

(II)–(i) After taking account of inequality (61), estimation of the left-hand side of inequality (49) implies

(62) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ¯ ( t ) ] κ + ξ t c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (62) and obtain

c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t = u ( t ) Y ¯ ( t ) c c u ρ ( t ) [ Y ¯ κ + δ ( t ) ] t ,

where u ( t ) = c t x ( s ) [ X ¯ ( s ) ] κ + ξ s . Using Y ¯ ( ) = 0 and u ( c ) = 0 yields

(63) c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t = c u ρ ( t ) [ Y ¯ κ + δ ( t ) ] t .

For Y ¯ ( t ) = x ( t ) C ( v ( t ) ) 0 , using the chain rule for the nabla derivative provides

(64) [ Y ¯ κ + δ ( t ) ] = 0 1 ( κ + δ ) Y ¯ ( t ) d h [ h Y ¯ ( t ) + ( 1 h ) Y ¯ ρ ( t ) ] 1 κ δ ( κ + δ ) x ( t ) C ( v ( t ) ) [ Y ¯ ( t ) ] κ + δ 1 ,

where we have used Y ¯ ( t ) 0 and Y ¯ ρ ( t ) Y ¯ ( t ) for κ + δ 1 and for all t [ c , ) T .

Then, one can obtain from inequality (56) that

(65) u ρ ( t ) = ρ ( t ) x ( s ) [ X ¯ ( s ) ] κ + ξ s D 3 κ + ξ ρ ( t ) [ X ¯ 1 κ ξ ( s ) ] 1 κ ξ s = D 3 κ + ξ [ X ¯ ρ ( t ) ] 1 κ ξ 1 κ ξ D 3 [ X ¯ ( t ) ] 1 κ ξ 1 κ ξ .

Then, inequality (63) reduces to

c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t D 3 ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ¯ ( t ) ] κ + δ 1 [ X ¯ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (49) after taking into account inequality (62).

(II)–(ii): After taking account of inequality (61), estimation of the left-hand side of inequality (50) implies

(66) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ¯ ρ ( t ) ] κ + ξ t c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (66) and obtain

c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t = u ( t ) Y ¯ ( t ) c c u ρ ( t ) [ Y ¯ κ + δ ( t ) ] t ,

where u ( t ) = c t x ( s ) [ X ¯ ρ ( s ) ] κ + ξ s . Using Y ¯ ( ) = 0 and u ( c ) = 0 yields

(67) c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t = c u ρ ( t ) [ Y ¯ κ + δ ( t ) ] t .

Then, one can obtain from inequality (57) that

u ρ ( t ) = c ρ ( t ) x ( s ) [ X ¯ ρ ( s ) ] κ + ξ s c ρ ( t ) [ X ¯ 1 κ ξ ( s ) ] 1 κ ξ s = [ X ¯ ρ ( t ) ] 1 κ ξ 1 κ ξ .

Then, substituting above inequality and inequality (64) to inequality (67) provides

c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t κ + δ 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ¯ ( t ) ] κ + δ 1 [ X ¯ ρ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (50) after taking into account inequality (66).□

Remark 3.8

When C ( z ) = z , inequalities (47)–(50) reduce to novel nabla Bennett-Leindler-type inequalities established if 0 < δ < 1 , κ 0 and 0 κ + ξ < 1 . Therefore, inequalities (47)–(50) are concave extensions of the nabla Bennett-Leindler-type inequalities. Moreover, they are converses of the nabla Pachpatte-type inequalities shown in (ii) of [61, Theorem 3].

Corollary 3.9

Let E 3 X ¯ ( t ) X ¯ σ ( t ) , t ( c , ) T be fulfilled for some E 3 > 0 and for X ¯ , X ¯ σ defined as in (31). Let 0 < δ < 1 , κ 0 , and 0 κ + ξ < 1 be real constants.

Then, nabla inequalities (47)–(50) turn into new delta inequalities. For a concave function C and for the functions X ¯ , V ¯ , and Y ¯ defined as in (31) and

  1. for 0 < κ + δ 1 , one can obtain

    1. (68) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ¯ σ ( t ) ] κ + ξ Δ t E 3 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ¯ σ ( t ) ] κ + ξ δ Δ t ,

    2. (69) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ¯ ( t ) ] κ + ξ Δ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ Δ t ,

  2. for κ + δ 1 , one can obtain

    1. (70) c x ( t ) C κ + δ ( V ¯ σ ( t ) ) [ X ¯ σ ( t ) ] κ + ξ Δ t E 3 ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ σ ( t ) ] κ [ X ¯ σ ( t ) ] κ + ξ δ Δ t ,

    2. (71) c x ( t ) C κ + δ ( V ¯ σ ( t ) ) [ X ¯ ( t ) ] κ + ξ Δ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ σ ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ Δ t .

When C ( z ) = z , inequalities (68)–(71) reduce to novel delta Bennett-Leindler-type inequalities established if 0 < δ < 1 , κ 0 , and 0 κ + ξ < 1 . Therefore, inequalities (68)–(71) are concave extensions of the delta Bennett-Leindler-type inequalities. Moreover, they are converses of the delta Pachpatte-type inequalities shown in (ii) of [61, Corollary 3] and (i) of [64, Remark 4].

Theorem 3.10

For the functions X ¯ , V ¯ , and Y ¯ defined in (11), let X ¯ ( t ) X ¯ ρ ( t ) D 4 , t ( c , ) T be fulfilled for some D 4 > 0 . If 0 < δ < 1 , κ 0 and κ + ξ 0 are real numbers, then for a nonnegative concave function C and

  1. for 0 < κ + δ 1 , we obtain

    1. (72) c x ( t ) C κ + δ ( V ¯ ρ ( t ) ) [ X ¯ ( t ) ] κ + ξ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ t ,

    2. (73) c x ( t ) C κ + δ ( V ¯ ρ ( t ) ) [ X ¯ ρ ( t ) ] κ + ξ t D 4 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ [ X ¯ ρ ( t ) ] κ + ξ δ t ,

  2. for κ + δ 1 , we obtain

    1. (74) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ¯ ( t ) ] κ + ξ t D 4 κ + ξ 1 ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ t ,

    2. (75) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ¯ ρ ( t ) ] κ + ξ t D 4 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ¯ ρ ( t ) ] κ + ξ δ t .

Proof

Using the same structure as suggested in the proof of Theorem 3.7 leads to the proof.

(I)–(i): After employing concavity of the function C and keeping the same ideas of the proof of (I)–(i) of Theorem 3.7, we reach inequality (53).

For X ¯ ( t ) = x ( t ) 0 , using the chain rule for the nabla derivative provides

(76) [ X ¯ 1 κ ξ ( t ) ] = 0 1 ( 1 κ ξ ) X ¯ ( t ) d h [ h X ¯ ( t ) + ( 1 h ) X ¯ ρ ( t ) ] κ + ξ ( 1 κ ξ ) x ( t ) [ X ¯ ( t ) ] κ + ξ ( 1 κ ξ ) x ( t ) [ X ¯ ρ ( t ) ] κ + ξ D 4 κ + ξ ,

where we have used X ¯ ( t ) 0 and X ¯ ρ ( t ) X ¯ ( t ) for κ + ξ 0 and for all t [ c , ) T .

Inequality (76) implies that

x ( t ) [ X ¯ ( t ) ] κ + ξ [ X ¯ 1 κ ξ ( t ) ] 1 κ ξ

and

(77) x ( t ) [ X ¯ ρ ( t ) ] κ + ξ D 4 κ + ξ [ X ¯ 1 κ ξ ( t ) ] 1 κ ξ .

By proceeding similar to the proof of Theorem 3.7 for the functions X ¯ and Y ¯ , the following is observed.

c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t κ + δ 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ + δ 1 [ X ¯ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (72).

(I)–(ii): After employing concavity of the function C and applying the similar ideas in the proof of (I)–(ii) of Theorem 3.7, we reach inequality (60).

Then, estimating the function u ρ by using inequality (77) and substituting the resulting inequality and inequality (54) to the inequality (60), we obtain

c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t D 4 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ + δ 1 [ X ¯ ( t ) ] κ + ξ 1 t D 4 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ + δ 1 [ X ¯ ρ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (73).

(II)–(i) After employing concavity of the function C and applying the similar ideas in the proof of (II)–(i) of Theorem 3.7, we arrive inequality (64).

Then, estimating the function u ρ by using inequality (77) and substituting the resulting inequality and inequality (64) to the inequality (63), we obtain

c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t D 4 κ + ξ 1 ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ¯ ( t ) ] κ + δ 1 [ X ¯ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (74).

(II)-(ii) After employing concavity of the function C and applying the similar ideas in the proof of (II)-(ii) of Theorem 3.7, we arrive inequality (67).

Then, estimating the function u ρ by using inequality (77) and substituting the resulting inequality and inequality (64) to the inequality (67), we obtain

c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t D 4 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) [ Y ¯ ( t ) ] κ + δ 1 [ X ¯ ρ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) for the constants 0 < δ < 1 implies inequality (75).□

Remark 3.11

When C ( z ) = z , inequalities (72)–(75) reduce to novel nabla Bennett-Leindler-type inequalities established if 0 < δ < 1 , κ 0 and κ + ξ 0 . Therefore, inequalities (72)–(75) are concave extensions of the nabla Bennett-Leindler-type inequalities. Moreover, they are converses of the nabla Pachpatte-type inequalities shown in (i) of [61, Theorem 3].

When C ( u ) = u , inequality (72) is a generalization of inequality (3.10) in [36, Theorem 3.9]. In addition to C ( z ) = z , if κ = 0 in inequality (37), then inequality (72) coincides inequality (3.10) in [36, Theorem 3.9].

Corollary 3.12

Let X ¯ σ ( t ) X ¯ ( t ) E 4 , t ( c , ) T be fulfilled for some E 4 > 0 and for X ¯ , X ¯ σ defined as in (31). Let 0 < δ < 1 , κ 0 and κ + ξ 0 be real constants.

Then, nabla inequalities (72)–(75) turn into new delta inequalities. For a concave function C and for the functions X ¯ , V ¯ , and Y ¯ defined as in (31) and

  1. for 0 < κ + δ 1 , we have

    1. (78) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ¯ σ ( t ) ] κ + ξ Δ t κ + δ 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ¯ σ ( t ) ] κ + ξ δ Δ t ,

    2. (79) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ¯ ( t ) ] κ + ξ Δ t E 4 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ Δ t ,

  2. for κ + δ 1 , one can obtain

    1. (80) c x ( t ) C κ + δ ( V ¯ σ ( t ) ) [ X ¯ σ ( t ) ] κ + ξ Δ t E 4 κ + ξ 1 ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ σ ( t ) ] κ [ X ¯ σ ( t ) ] κ + ξ δ Δ t ,

    2. (81) c x ( t ) C κ + δ ( V ¯ σ ( t ) ) [ X ¯ ( t ) ] κ + ξ Δ t E 4 κ + ξ ( κ + δ ) 1 κ ξ δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ σ ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ Δ t .

When C ( z ) = z , inequalities (78)–(81) reduce to novel delta Bennett-Leindler-type inequalities established if 0 < δ < 1 , κ 0 , and κ + ξ 0 . Therefore, inequalities (78)–(81) are concave extensions of the delta Bennett-Leindler-type inequalities. Moreover, they are converses of the delta Pachpatte-type inequalities shown in (i) of [61, Corollary 3] and (ii) of [64, Remark 4].

When C ( z ) = z , inequality (78) is a generalization of inequality (2.23) in [58, Theorem 2.3]. In addition to C ( z ) = z , if κ = 0 in inequality (78), then inequality (78) coincides inequality (2.23) in [58, Theorem 2.3].

Theorem 3.13

For the functions X , V ¯ , and Y ¯ defined in (11) and for the constant D 1 defined in Theorem 3.1, if 0 < δ < 1 , κ 0 , and κ + ξ 1 are real numbers, then for a nonnegative concave function C and

  1. for 0 < κ + δ 1 , we have

    1. (82) c x ( t ) C κ + δ ( V ¯ ρ ( t ) ) [ X ( t ) ] κ + ξ t κ + δ κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ [ X ( t ) ] κ + ξ δ t ,

    2. (83) c x ( t ) C κ + δ ( V ¯ ρ ( t ) ) [ X ρ ( t ) ] κ + ξ t D 1 κ + ξ ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ [ X ρ ( t ) ] κ + ξ δ t ,

  2. for κ + δ 1 , we have

    1. (84) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ( t ) ] κ + ξ t D 1 κ + ξ 1 ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ( t ) ] κ + ξ δ t ,

    2. (85) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ρ ( t ) ] κ + ξ t D 1 κ + ξ ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ρ ( t ) ] κ + ξ δ t .

Proof

We combine the proofs of Theorems 3.4 and 3.10.

(I)-(i): After taking account of inequality (51), estimation of the left-hand side of inequality (82) implies

(86) c x ( t ) C κ + δ ( V ¯ ρ ( t ) ) [ X ( t ) ] κ + ξ t c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (86) and obtain

c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t = u ( t ) Y ¯ ( t ) c c u ( t ) [ Y ¯ κ + δ ( t ) ] t ,

where u ( t ) = c t x ( s ) [ X ( s ) ] κ + ξ s . Using Y ¯ ( ) = 0 and u ( c ) = 0 yields

(87) c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t = c u ( t ) [ Y ¯ κ + δ ( t ) ] t .

For X ( t ) = x ( t ) 0 , using the chain rule for the nabla derivative provides

(88) [ X 1 κ ξ ( t ) ] = 0 1 ( 1 κ ξ ) X ( t ) d h [ h X ( t ) + ( 1 h ) X ρ ( t ) ] κ + ξ ( κ + ξ 1 ) x ( t ) [ X ( t ) ] κ + ξ ( κ + ξ 1 ) x ( t ) [ X ρ ( t ) ] κ + ξ D 1 κ + ξ ,

where we have used X ( t ) 0 and X ρ ( t ) X ( t ) for κ + ξ 1 and for all t [ c , ) T .

Inequality (88) implies that

(89) x ( t ) [ X ( t ) ] κ + ξ [ X 1 κ ξ ( t ) ] κ + ξ 1

and

(90) x ( t ) [ X ρ ( t ) ] κ + ξ D 1 κ + ξ [ X 1 κ ξ ( t ) ] κ + ξ 1 .

Then, one can obtain from inequality (89) that

(91) u ( t ) = c t x ( s ) [ X ( s ) ] κ + ξ s c t [ X 1 κ ξ ( s ) ] κ + ξ 1 s = [ X ( t ) ] 1 κ ξ κ + ξ 1 .

Then, combination of inequality (54) and inequality (91) in inequality (87) reduces to

c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t κ + δ κ + ξ 1 c x ( t ) C ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ + δ 1 [ X ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) implies inequality (82).

(I)-(ii): After taking account of inequality (51), estimation of the left-hand side of inequality (83) implies

(92) c x ( t ) C κ + δ ( V ¯ ρ ( t ) ) [ X ρ ( t ) ] κ + ξ t c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (92) and obtain

c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t = u ( t ) Y ¯ ( t ) c c u ( t ) [ Y ¯ κ + δ ( t ) ] t ,

where u ( t ) = c t x ( s ) [ X ρ ( s ) ] κ + ξ s . Using Y ¯ ( ) = 0 and u ( c ) = 0 yields

(93) c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t = c u ( t ) [ Y ¯ κ + δ ( t ) ] t .

Then, one can obtain from inequality (90) that

u ( t ) = c t x ( s ) [ X ρ ( s ) ] κ + ξ s D 1 κ + ξ c t [ X κ + ξ ( s ) ] κ + ξ 1 s = D 1 κ + ξ [ X ( t ) ] 1 κ ξ κ + ξ 1 D 1 κ + ξ [ X ρ ( t ) ] κ + ξ 1 κ + ξ 1 .

Then, substituting the above inequality and inequality (54) to inequality (93) provides

c x ( t ) [ Y ¯ ρ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t D 1 κ + ξ ( κ + δ ) κ + ξ 1 c x ( t ) C ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ + δ 1 [ X ρ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) implies inequality (83).

Now, we prove (II).

(II)-(i): From inequality (61), the left-hand side of inequality (84) can be estimated as

(94) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ( t ) ] κ + ξ t c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (94) and obtain

c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t = u ( t ) Y ¯ ( t ) c c u ρ ( t ) [ Y ¯ κ + δ ( t ) ] t ,

where u ( t ) = c t x ( s ) [ X ( s ) ] κ + ξ s . Using Y ¯ ( ) = 0 and u ( c ) = 0 yields

c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t = c u ρ ( t ) [ Y ¯ κ + δ ( t ) ] t .

Then, one can obtain from inequality (89) that

u ρ ( t ) = ρ ( t ) x ( s ) [ X ( s ) ] κ + ξ s ρ ( t ) [ X 1 κ ξ ( s ) ] κ + ξ 1 s = [ X ρ ( t ) ] 1 κ ξ κ + ξ 1 D 1 κ + ξ [ X ( t ) ] 1 κ ξ κ + ξ 1 .

Then, substituting the above inequality and inequality (64) to inequality (93) provides

c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ( t ) ] κ + ξ t D 1 κ + ξ ( κ + δ ) κ + ξ 1 c x ( t ) C ( v ( t ) ) [ Y ¯ ( t ) ] κ + δ 1 [ X ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) implies inequality (84).

(II)-(ii): From inequality (61), the left-hand side of inequality (85) can be estimated as

c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ρ ( t ) ] κ + ξ t c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (66) and obtain

c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t = u ( t ) Y ¯ ( t ) c c u ρ ( t ) [ Y ¯ κ + δ ( t ) ] t ,

where u ( t ) = c t x ( s ) [ X ρ ( s ) ] κ + ξ s . Using Y ¯ ( ) = 0 and u ( c ) = 0 yields

(95) c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t = c u ρ ( t ) [ Y ¯ κ + δ ( t ) ] t .

Then, one can obtain from inequality (90) that

u ρ ( t ) = c ρ ( t ) x ( s ) [ X ρ ( s ) ] κ + ξ s D 1 κ + ξ c ρ ( t ) [ X 1 κ ξ ( s ) ] κ + ξ 1 s = D 1 κ + ξ [ X ρ ( t ) ] 1 κ ξ κ + ξ 1 .

Then, substituting the above inequality and inequality (64) to inequality (95) provides

c x ( t ) [ Y ¯ ( t ) ] κ + δ [ X ρ ( t ) ] κ + ξ t D 1 κ + ξ ( κ + δ ) κ + ξ 1 c x ( t ) C ( v ( t ) ) [ Y ¯ ( t ) ] κ + δ 1 [ X ρ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) implies inequality (85).□

Remark 3.14

When C ( z ) = z , inequalities (82)–(85) reduce to novel nabla Bennett-Leindler-type inequalities established if 0 < δ < 1 , κ 0 and κ + ξ 1 . Therefore, inequalities (82)–(85) are concave extensions of the nabla Bennett-Leindler-type inequalities. Moreover, they are converses of the nabla Pachpatte-type inequalities shown in (i) of [61, Theorem 2].

When C ( u ) = u , inequality (84) is a generalization of inequality (3.15) in [36, Theorem 3.12]. In addition to C ( z ) = z , if κ = 0 in inequality (84), then inequality (84) coincides inequality (3.15) in [36, Theorem 3.12].

Remark 3.15

Inequality (83) can also be obtained as follows:

c x ( t ) C κ + δ V ¯ ρ ( t ) X ρ ( t ) [ X ρ ( t ) ] ξ δ t D 1 κ + ξ ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ρ ( t ) ] κ [ X ρ ( t ) ] κ + ξ δ t .

Inequality (84) can also be obtained as follows:

c x ( t ) C κ + δ V ¯ ( t ) X ( t ) [ X ( t ) ] ξ δ t D 1 κ + ξ 1 ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ( t ) ] κ + ξ δ t .

Corollary 3.16

Let the constant E 1 > 0 be defined as in Corollary 3.3 and 0 < δ < 1 , κ 0 , and κ + ξ 1 be real constants.

Then, nabla inequalities (82)–(85) turn into new delta inequalities. For a concave function C and for the functions X , V ¯ , and Y ¯ defined as in (31) and

  1. for 0 < κ + δ 1 , one can obtain

    1. (96) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X σ ( t ) ] κ + ξ Δ t κ + δ κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X σ ( t ) ] κ + ξ δ Δ t ,

    2. (97) c x ( t ) C κ + δ ( V ¯ ( t ) ) [ X ( t ) ] κ + ξ Δ t E 1 κ + ξ ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ ( t ) ] κ [ X ( t ) ] κ + ξ δ Δ t ,

  2. for κ + δ 1 , one can obtain

    1. (98) c x ( t ) C κ + δ ( V ¯ σ ( t ) ) [ X σ ( t ) ] κ + ξ Δ t E 1 κ + ξ 1 ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ σ ( t ) ] κ [ X σ ( t ) ] κ + ξ δ Δ t ,

    2. (99) c x ( t ) C κ + δ ( V ¯ σ ( t ) ) [ X ( t ) ] κ + ξ Δ t E 1 κ + ξ ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ¯ σ ( t ) ] κ [ X ( t ) ] κ + ξ δ Δ t .

When C ( z ) = z , inequalities (96)–(99) reduce to novel delta Bennett-Leindler-type inequalities establihed if 0 < δ < 1 , κ 0 , and κ + ξ 1 . Therefore, inequalities (96)–(99) are concave extensions of the delta Bennett-Leindler-type inequalities. Moreover, they are converses of the delta Pachpatte-type inequalities shown in (i) of [61, Corollary 2] and (i) of [64, Remark 8].

When C ( u ) = u , inequality (97) is a generalization of inequality (2.15) in [58, Theorem 2.2]. In addition to C ( z ) = z , if κ = 0 in inequality (97), then inequality (97) coincides inequality (2.15) in [58, Theorem 2.2].

Theorem 3.17

For the functions X ¯ , V , and Y defined in (11), and for the constant D 3 > 0 defined in Theorem 3.7, if 0 < δ < 1 , κ 0 , and κ + ξ 1 are real numbers, then for a nonnegative concave function C and

  1. for 0 < κ + δ 1 , we obtain

    1. (100) c x ( t ) C κ + δ ( V ( t ) ) [ X ¯ ( t ) ] κ + ξ t D 3 κ + ξ ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) Y κ ( t ) [ X ¯ ( t ) ] κ + ξ δ t ,

    2. (101) c x ( t ) C κ + δ ( V ( t ) ) [ X ¯ ρ ( t ) ] κ + ξ t κ + δ κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) Y κ ( t ) [ X ¯ ρ ( t ) ] κ + ξ δ t ,

  2. for κ + δ 1 , we obtain

    1. (102) c x ( t ) C κ + δ ( V ρ ( t ) ) [ X ¯ ( t ) ] κ + ξ t D 3 κ + ξ ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ρ ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ t ,

    2. (103) c x ( t ) C κ + δ ( V ρ ( t ) ) [ X ¯ ρ ( t ) ] κ + ξ t D 3 κ + ξ 1 ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ρ ( t ) ] κ [ X ¯ ρ ( t ) ] κ + ξ δ t .

Proof

We combine the proofs of Theorems 3.4 and 3.10.

(I)-(i) After taking account of inequality (16), estimation of the left-hand side of inequality (100) implies

(104) c x ( t ) C κ + δ ( V ( t ) ) [ X ¯ ( t ) ] κ + ξ t c x ( t ) Y κ + δ ( t ) [ X ¯ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (104) and obtain

c x ( t ) Y κ + δ ( t ) [ X ¯ ( t ) ] κ + ξ = u ( t ) Y ( t ) c c u ρ ( t ) [ Y κ + δ ( t ) ] t ,

where u ( t ) = t x ( s ) [ X ¯ ( s ) ] κ + ξ s . Using Y ( c ) = 0 and u ( ) = 0 yields

(105) c x ( t ) Y κ + δ ( t ) [ X ¯ ( t ) ] κ + ξ = c u ρ ( t ) [ Y κ + δ ( t ) ] t .

For X ¯ ( t ) = x ( t ) 0 , using the chain rule for the nabla derivative provides

(106) [ X ¯ 1 κ ξ ( t ) ] = 0 1 ( 1 κ ξ ) X ¯ ( t ) d h [ h X ¯ ( t ) + ( 1 h ) X ¯ ρ ( t ) ] κ + ξ ( κ + ξ 1 ) x ( t ) [ X ¯ ρ ( t ) ] κ + ξ ( κ + ξ 1 ) x ( t ) [ X ¯ ( t ) ] κ + ξ D 3 κ + ξ ,

where X ¯ ( t ) 0 and X ¯ ρ ( t ) X ¯ ( t ) have been used for κ + ξ 1 and for all t [ c , ) T .

Inequality (106) implies that

(107) x ( t ) [ X ¯ ρ ( t ) ] κ + ξ [ X ¯ 1 κ ξ ( t ) ] κ + ξ 1

and

(108) x ( t ) [ X ¯ ( t ) ] κ + ξ D 3 κ + ξ [ X ¯ 1 κ ξ ( t ) ] κ + ξ 1 .

Then, one can obtain from inequality (108) that

(109) u ρ ( t ) = ρ ( t ) x ( s ) [ X ¯ ( s ) ] κ + ξ s D 3 κ + ξ κ + ξ 1 ρ ( t ) [ X ¯ 1 κ ξ ( s ) ] s = D 3 κ + ξ κ + ξ 1 [ X ¯ ρ ( t ) ] 1 κ ξ D 3 κ + ξ κ + ξ 1 [ X ¯ ( t ) ] 1 κ ξ .

Then, combination of inequality (109) and inequality (19) in inequality (105) provides

c x ( t ) Y κ + δ ( t ) [ X ¯ ( t ) ] κ + ξ D 3 κ + ξ ( κ + δ ) 1 κ ξ c x ( t ) C ( v ( t ) ) Y κ + δ 1 ( t ) [ X ¯ ( t ) ] κ + ξ 1 .

The reverse Hölder inequality (9) implies inequality (100).

(I)-(ii) After taking account of inequality (16), estimation of the left-hand side of inequality (101) implies

(110) c x ( t ) C κ + δ ( V ( t ) ) [ X ¯ ρ ( t ) ] κ + ξ t c x ( t ) Y κ + δ ( t ) [ X ¯ ρ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (110) and obtain

c x ( t ) Y κ + δ ( t ) [ X ¯ ρ ( t ) ] κ + ξ t = u ( t ) Y ( t ) c c u ρ ( t ) [ Y κ + δ ( t ) ] t ,

where u ( t ) = t x ( s ) [ X ¯ ρ ( s ) ] κ + ξ s . Using Y ( c ) = 0 and u ( ) = 0 yields

(111) c x ( t ) Y κ + δ ( t ) [ X ¯ ρ ( t ) ] κ + ξ t = c u ρ ( t ) [ Y κ + δ ( t ) ] t .

Then, one can obtain from inequality (107) that

(112) u ρ ( t ) = ρ ( t ) x ( s ) [ X ¯ ρ ( s ) ] κ + ξ s ρ ( t ) [ X ¯ 1 κ ξ ( t ) ] κ + ξ 1 s = [ X ¯ ρ ( s ) ] 1 κ ξ κ + ξ 1 .

Then, combination of inequality (112) and inequality (19) in inequality (111) provides

c x ( t ) Y κ + δ ( t ) [ X ¯ ρ ( t ) ] κ + ξ t κ + δ κ + ξ 1 c x ( t ) C ( v ( t ) ) Y κ + δ 1 ( t ) [ X ¯ ρ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) implies inequality (101).

(II)-(i): After taking account of inequality (25), estimation of the left-hand side of inequality (102) implies

(113) c x ( t ) C κ + δ ( V ρ ( t ) ) [ X ¯ ( t ) ] κ + ξ t c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (113) and obtain

c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t = u ( t ) Y ( t ) c c u ( t ) [ Y κ + δ ( t ) ] t ,

where u ( t ) = t x ( s ) [ X ¯ ( s ) ] κ + ξ s . Using Y ( c ) = 0 and u ( ) = 0 yields

(114) c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t = c u ( t ) [ Y κ + δ ( t ) ] t .

Then, one can obtain from inequality (107) that

(115) u ( t ) = t x ( s ) [ X ¯ ( s ) ] κ + ξ s D 3 κ + ξ κ + ξ 1 t [ X ¯ 1 κ ξ ( s ) ] s = D 3 κ + ξ κ + ξ 1 X ¯ 1 κ ξ ( t ) .

Then, substituting inequality (115) and inequality (28) to inequality (114) provides

c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ¯ ( t ) ] κ + ξ t = D 3 κ + ξ ( κ + δ ) κ + ξ 1 c x ( t ) C ( v ( t ) ) [ Y ρ ( t ) ] κ + δ 1 X ¯ κ + ξ 1 ( t ) t .

The reverse Hölder inequality (9) implies inequality (102).

(II)-(ii): From inequality (25), the left-hand side of inequality (103) can be estimated as

(116) c x ( t ) C κ + δ ( V ρ ( t ) ) [ X ¯ ρ ( t ) ] κ + ξ t c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t .

In order to obtain nabla Bennett-Leindler-type inequalities, we apply integration by parts formula to the right-hand side of inequality (116) and obtain

c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t = u ( t ) Y ( t ) c c u ( t ) [ Y κ + δ ( t ) ] t ,

where u ( t ) = t x ( s ) [ X ¯ ρ ( s ) ] κ + ξ s . Using Y ( c ) = 0 and u ( ) = 0 yields

(117) c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t = c u ( t ) [ Y κ + δ ( t ) ] t .

Then, one can obtain from inequality (107) that

(118) u ( t ) = t x ( s ) [ X ¯ ρ ( s ) ] κ + ξ s t [ X ¯ 1 κ ξ ( s ) ] κ + ξ 1 s = D 3 κ + ξ [ X ¯ ρ ( t ) ] 1 κ ξ κ + ξ 1 .

Then, substituting inequality (118) and inequality (28) to inequality (117) provides

c x ( t ) [ Y ρ ( t ) ] κ + δ [ X ¯ ρ ( t ) ] κ + ξ t D 3 κ + ξ ( κ + δ ) κ + ξ 1 c x ( t ) C ( v ( t ) ) [ Y ρ ( t ) ] κ + δ 1 [ X ¯ ρ ( t ) ] κ + ξ 1 t .

The reverse Hölder inequality (9) implies inequality (103).□

Remark 3.18

When C ( z ) = z , inequalities (100)–(103) reduce to novel nabla Bennett-Leindler-type inequalities established if 0 < δ < 1 , κ 0 and κ + ξ 1 . Therefore, inequalities (100)–(103) are concave extensions of the nabla Bennett-Leindler-type inequalities. Moreover, they are converses of the nabla Pachpatte-type inequalities shown in (iii)-(iv) of [61, Theorem 1] and (i) of [64, Remark 6].

When C ( z ) = z , inequality (100) is a generalization of inequality (3.15) in [36, Theorem 3.12]. In addition to C ( z ) = z , if κ = 0 in inequality (100), then inequality (100) coincides inequality (3.15) in [36, Theorem 3.12].

Remark 3.19

Inequality (100) can also be obtained as follows:

c x ( t ) C κ + δ V ( t ) X ¯ ( t ) [ X ¯ ( t ) ] ξ δ t D 3 κ + ξ ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ t .

Inequality (103) can also be obtained as follows.

c x ( t ) C κ + δ V ρ ( t ) X ¯ ρ ( t ) [ X ¯ ρ ( t ) ] ξ δ t D 3 κ + ξ 1 ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ρ ( t ) ] κ [ X ¯ ρ ( t ) ] κ + ξ δ t .

Corollary 3.20

Let the constant E 3 be defined in Corollary 3.9 and 0 < δ < 1 , κ 0 and κ + ξ 1 be real constants.

Then, nabla inequalities (100)–(103) turn into new delta inequalities. For a concave function C and for the functions X ¯ , V , and Y defined as in (31) and

  1. for 0 < κ + δ 1 , we have

    1. (119) c x ( t ) C κ + δ ( V σ ( t ) ) [ X ¯ σ ( t ) ] κ + ξ Δ t E 3 κ + ξ ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y σ ( t ) ] κ [ X ¯ σ ( t ) ] κ + ξ δ Δ t ,

    2. (120) c x ( t ) C κ + δ ( V σ ( t ) ) [ X ¯ ( t ) ] κ + ξ Δ t κ + δ κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y σ ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ Δ t

  2. for κ + δ 1 , one can obtain

    1. (121) c x ( t ) C κ + δ ( V ( t ) ) [ X ¯ σ ( t ) ] κ + ξ Δ t E 3 κ + ξ ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ( t ) ] κ [ X ¯ σ ( t ) ] κ + ξ δ Δ t ,

    2. (122) c x ( t ) C κ + δ ( V ( t ) ) [ X ¯ ( t ) ] κ + ξ Δ t E 3 κ + ξ 1 ( κ + δ ) κ + ξ 1 δ c x ( t ) C δ ( v ( t ) ) [ Y ( t ) ] κ [ X ¯ ( t ) ] κ + ξ δ Δ t .

When C ( z ) = z , inequalities (119)–(122) reduce to novel delta Bennett-Leindler-type inequalities established if 0 < δ < 1 , κ 0 , and κ + ξ 1 . Therefore, inequalities (119)–(122) are concave extensions of the delta Bennett-Leindler-type inequalities. Moreover, they are converses of the delta Pachpatte-type inequalities shown in (ii) of [61, Corollary 1].

When C ( z ) = z , inequality (119) is a generalization of inequality (2.30) in [58, Theorem 2.4]. In addition to C ( z ) = z , if κ = 0 in inequality (119), then inequality (119) coincides inequality (2.30) in [58, Theorem 2.4].

4 Conclusion

Since time scale calculus enables us to avoid the separate discussion of the two cases, which are continuous and discrete cases, the unification of these cases by nabla calculus has gained importance in recent years.

Moreover, convexity/concavity play key roles in functional analysis, optimization and control theory.

In this article, concave generalizations of nabla Bennett-Leindler-type inequalities, which are analagous to the results of the delta time scale calculus and are unifications of the related continuous and discrete results, were established. These novel nabla inequalities not only provided new delta, continuous and discrete results but also could serve as starting points for the new results in diamond alpha calculus, which is a linear combination of delta and nabla time scale calculi.

Acknowledgments

The authors are very grateful to the referees for the valuable comments and remarks which provide valuable insights and helped to polish the content of the article and improve its quality.

  1. Funding information: The authors state no funding involved.

  2. Author contributions: All authors accept responsibility for the entire content of this manuscript and approve its submission.

  3. Conflict of interest: The author states no conflict of interest.

  4. Ethical approval: The conducted research is not related to either human or animal use.

  5. Data availability statement: No data is associated with this research.

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Received: 2023-08-31
Revised: 2024-04-23
Accepted: 2025-02-24
Published Online: 2025-03-25

© 2025 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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