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Page 1: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

Commun. Korean Math. Soc. 35 (2020), No. 1, pp. 161–184

https://doi.org/10.4134/CKMS.c180458

pISSN: 1225-1763 / eISSN: 2234-3024

ON SOME WEIGHTED HARDY-TYPE INEQUALITIES

INVOLVING EXTENDED RIEMANN-LIOUVILLE

FRACTIONAL CALCULUS OPERATORS

Sajid Iqbal, Josip Pecaric, Muhammad Samraiz, Hassan Tehmeena,and Zivorad Tomovski

Abstract. In this article, we establish some new weighted Hardy-type

inequalities involving some variants of extended Riemann-Liouville frac-

tional derivative operators, using convex and increasing functions. Asspecial cases of the main results, we obtain the results of [18,19]. We also

prove the boundedness of the k-fractional integral operator on Lp[a, b].

1. Introduction

Fractional calculus deals with the non integer order derivative and integraloperators and draws increasing attention due to its applications in many fieldssee e.g. the books [30, 31]. The first application of fractional calculus was dueto Abel in his solution to the Tautocrone problem [1]. It also has applicationsin biophysics, quantum mechanics, wave theory, polymers, continuum mechan-ics, Lie theory, field theory, spectroscopy and in group theory, among otherapplications [14–16,25].

Many mathematicians originate the Hardy-type inequalities for differentfractional integral and derivative operators. Because of the fundamental impor-tance of such inequalities in technical sciences, over the years much effort andtime have been dedicated to the improvement and generalizations of Hardy-type inequalities. But still there are many open questions in this area, see e.g.those pointed out in [24, Section 7.5]. For further details and literature aboutthe rich history of Hardy-type inequalities and fractional calculus, we refer thebooks [4,13,15] and the papers [2,6,7,10,18,20]. In the present work, we shallintroduce some new results concerning Hardy-type inequalities not covered bythe literature mentioned above.

Received November 7, 2018; Revised February 19, 2019; Accepted March 11, 2019.

2010 Mathematics Subject Classification. 26D15, 26D10, 26A33.Key words and phrases. Hardy-type inequalities, Riemann-Liouville, fractional integral

operator, convex and increasing function.The research of second author was supported by the Ministry of Education and Science

of the Russian Federation (Agreement number No. 02.a03.21.0008).

c©2020 Korean Mathematical Society

161

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162 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

2. Preliminaries and basic results

We start with the definition of the Riemann-Liouville fractional integrals(see [22]).

Definition 2.1. Let [a, b], (−∞ < a < b < ∞) be a finite interval on thereal axis R. The Riemann-Liouville fractional integrals Iαa+f and Iαb−f of order

α > 0 are defined by

(Iαa+f)(x) =1

Γ(α)

∫ x

a

f(t)(x− t)α−1dt, (x > a)

and

(Iαb−f)(x) =1

Γ(α)

∫ b

x

f(t)(t− x)α−1dt, (x < b),

respectively. Here Γ is the usual gamma function.

These integrals are called the left-sided and the right-sided fractional inte-grals and are bounded in Lp(a, b), 1 ≤ p ≤ ∞, that is

(2.1) ‖Iαa+f‖p ≤ K‖f‖p, ‖Iαb−f‖p ≤ K‖f‖p,where

K =(b− a)α

Γ(α+ 1).

Inequalities given in (2.1) were proved by Hardy in one of his paper [12].Next is the definition of convex function presented in [13].

Definition 2.2. Let I be an interval in R. A function Φ : I → R is calledconvex if the following inequality

(2.2) Φ(λx+ (1− λ)t) ≤ λΦ(x) + (1− λ)Φ(t)

holds for all points x, y ∈ I and all λ ∈ [0, 1]. The function Φ is strictly convexif inequality (2.2) holds strictly for all distinct points in I and λ ∈ (0, 1).

The generalized Lp space given in [28] defined as follows:

Definition 2.3. A space Lp,r[a, b] is defined as a space of continuous realvalued function h(t) on [a, b], such that(∫ b

a

|h(t)|ptrdt

) 1p

<∞,

where 1 ≤ p <∞, r ≥ 0. It is clearly seems that Lp,0[a, b] = Lp[a, b].

Following is the definition of gamma k function defined by Diaz et al. in [9].

Definition 2.4. The Γk function is the generalization of the classical Γ functionand is defined as follows:

(2.3) Γk(t) = limn→∞

n!kn(nk)tk−1

(t)n,k, k > 0, R(t) > 0,

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ON SOME WEIGHTED HARDY-TYPE INEQUALITIES 163

where (t)n,k = t(t+ k)(t+ 2k) · · · (t+ (n− 1)k), n ≥ 1, is called Pochhammerk symbol. The integral representation is given by

(2.4) Γk(t) =

∫ ∞0

xt−1e−xkk dx, R(t) > 0.

Specially for k = 1, Γ1(t) = Γ(t).

Next is the well known definition of Riemann-Liouvill fractional derivative(see [22], [32]) of order α defined by

Dαxf(x) =

1

Γ(−α)

∫ x

0

f(t)(x− t)−α−1dt, R(α) < 0.

Let (Σ1,Ω1, µ1) and (Σ2,Ω2, µ2) be measure spaces with positive σ-finite mea-sures. Let U(f) denote the class of functions g : Ω1 → R with the representation

g(x) :=

∫Ω2

k(x, t)f(t)dµ2(t)

and Ak be an integral operator defined by

(2.5) Akf(x) :=g(x)

K(x)=

1

K(x)

∫Ω2

k(x, t)f(t)dµ2(t),

where k : Ω1 × Ω2 → R is measurable and non-negative kernel, f : Ω2 → R isa measurable function and

(2.6) 0 < K(x) :=

∫Ω2

k(x, t)dµ2(t), x ∈ Ω1.

The following theorem is given in [18].

Theorem 2.5. Let (Σ1,Ω1, µ1) and (Σ2,Ω2, µ2) be measure spaces with σ-finite measures, u be a weight function on Ω1, k be a non-negative measurable

kernel on Ω1 × Ω2. Let 0 < p ≤ q < ∞ and the function x 7→ u(x)k(x,t)K(x) is

integrable on Ω1. Then for each fixed t ∈ Ω2, v is known by

v(t) :=

∫Ω1

u(x)k(x, t)

K(x)dµ1(x) <∞.

If Φ : (0,∞)→ R is a convex and increasing function, then the inequality∫Ω1

u(x)Φ

(∣∣∣∣ g(x)

K(x)

∣∣∣∣) dµ1(x) ≤∫

Ω2

v(t)Φ(|f(t)|)dµ2(t)

holds for all measurable functions f : Ω2 → R.

Next result is specified in [19].

Theorem 2.6. Let fi : Ω2 → R be measurable functions, gi ∈ U(fi), (i = 1, 2),where g2(x) > 0 for every x ∈ Ω1. Let u be a weight function on Ω1 and

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164 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

k a non-negative measurable kernel on Ω1 × Ω2. Assume that the function

x 7→ u(x) f2(t)k(x,t)g2(x) is integrable on Ω1 for each fixed t ∈ Ω2. Define p on Ω2 by

p(t) := f2(t)

∫Ω1

u(x)k(x, t)

g2(x)dµ1(x) <∞.

If Φ : (0,∞)→ R is a convex and increasing function, then the inequality∫Ω1

u(x)Φ

(∣∣∣∣g1(x)

g2(x)

∣∣∣∣) dµ1(x) ≤∫

Ω2

p(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣) dµ2(t)

holds.

The inequality due to Krulic et al. [23] is given in the following theorem.

Theorem 2.7. Let the assumptions of Theorem 2.5 be satisfied and w be de-fined by

w(t) :=

[∫Ω1

u(x)

(k(x, t)

K(x)

) qp

dµ1(x)

] pq

<∞.

If Φ is a non-negative convex function on the interval I ⊆ R, then the inequality[∫Ω1

u(x) (Φ (Akf(x)))qp dµ1(x)

] 1q

≤[∫

Ω2

w(t)Φ (f(t)) dµ2(t)

] 1p

holds for all measurable functions f : Ω2 → R such that Imf ⊆ I.

The following theorem is given in [23].

Theorem 2.8. Let gi ∈ U(fi), (i = 1, 2, 3), where g2(x) > 0 for every x ∈ Ω1.Let u be a weight function on Ω1, k be a non-negative measurable function onΩ1 × Ω2. Then r is defined by

r(t) := f2(t)

∫Ω1

u(x)k(x, t)

g2(x)dx <∞.

If Φ : (0,∞) × (0,∞) → R is a convex and increasing function, then theinequality∫

Ω1

u(x)Φ

(∣∣∣∣g1(x)

g2(x)

∣∣∣∣ , ∣∣∣∣g3(x)

g2(x)

∣∣∣∣) dµ1(x) ≤∫

Ω2

r(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣ , ∣∣∣∣f3(t)

f2(t)

∣∣∣∣) dµ2(t)

holds true.

3. Weighted Hardy-type integral inequalities for extendedRiemann-Liouville fractional derivative operator involving

exponential function

This section consists of weighted Hardy-type inequalities for the extendedRiemann-Liouville fractional derivative operator established in [5] and is de-fined as follows:

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ON SOME WEIGHTED HARDY-TYPE INEQUALITIES 165

Definition 3.1. Let R(r) > 0, R(s) > 0 and R(α) < 0. Then the extendedRiemann-Liouville fractional derivative Dα

xf(x); r, s of order α, be such that

(3.1) Dαxf(x); r, s =

1

Γ(−α)

∫ x

0

f(t)(x− t)−α−1 exp

(−rxt− sx

(x− t)

)dt.

Specially for r = s we arrive at the extended Riemann-Liouville fractionalderivative of order α given in [3] and is defined by

(3.2) Dαxf(x); r =

1

Γ(−α)

∫ x

0

f(t)(x− t)−α−1 exp

(− rx2

t(x− t)

)dt.

Example 3.2. Consider the derivative given by (3.1) of xν corresponding tox = 1, we get

Dαxxν ; r, sx=1 =

Br,s(ν + 1,−α)

Γ(−α),

where Br,s(ν + 1,−α) is the extended beta functions (see [26]) defined by

(3.3) Br,s(x, y) =

∫ 1

0

tx−1(1− t)y−1e−rt−

s1−t dt,

where x, y, r, s ∈ C, R(r) > 0, R(s) > 0. For r = s, Br,s becomes Br and forr = s = 0, we get the classical beta function defined by

B(x, y) =

∫ 1

0

tx−1(1− t)y−1dt, R(x) > 0, R(y) > 0.

In [29] the following inequality is proved for the extended beta function (3.3):

Br,s(x, y) ≤ (2r)2x−1

2 (2s)2y−1

2

√Γ(−2x+ 1, 2r)Γ(−2y + 1, 2s),

where r, s > 0, 0 < x, y < 12 and Γ(x, y) is the incomplete gamma function.

Lemma 3.3. Let R(r) > 0, R(s) > 0 and R(α) < 0. Then the followingrelation holds:

K(x) =x−αBr,s(1,−α)

Γ(−α).(3.4)

Proof. Since

(3.5) k(x, t) =

1

Γ(−α) (x− t)−α−1 exp(− rxt −

sx(x−t)

), 0 ≤ t ≤ x ;

0, x < t ≤ b .Therefore

K(x) =1

Γ(−α)

∫ x

0

(x− t)−α−1 exp

(−rxt− sx

(x− t)

)dt,

which can be written as

=x−α−1

Γ(−α)

∫ x

0

(1− t

x)−α−1 exp

(−rxt− s

(1− tx )

)dt.

By substituting tx = y and using the simple calculation, we arrive at (3.4).

Page 6: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

166 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

The first result for the operator (3.1) is as follows:

Theorem 3.4. Let R(r) > 0, R(s) > 0 and R(α) < 0. Let Dαxf(x); r, s

denote the extension of Riemann-Liouville fractional derivative of order α andlet u be a weight function defined on (0, b). For each fixed t ∈ (0, b), define afunction v by

v(t) =

∫ b

t

u(x)(x− t)−α−1 exp

(− rxt −

sx(x−t)

)x−αBr,s(1,−α)

dx <∞.

If Φ : (0,∞)→ R is a convex and increasing function, then the inequality

(3.6)

∫ b

0

u(x)Φ

(∣∣∣∣Γ(−α)Dαxf(x); r, s

x−αBr,s(1,−α)

∣∣∣∣) dx ≤ ∫ b

0

v(t)Φ(|f(t)|)dt

holds for all measurable functions f ∈ L1(a, b).

Proof. Applying Theorem 2.5 with Ω1 = Ω2 = (0, b), dµ1(x) = dx, dµ2(t) = dt,

K(x), k(x, t) given in (3.4), (3.5), respectively and define

(3.7) Akf(x) =Γ(−α)Dα

xf(x); r, sx−αBr,s(1,−α)

,

we get inequality (3.6).

Theorem 3.5. Let R(r) > 0, R(s) > 0 and R(α) < 0. Let Dαxf(x); r, s

denote the extension of Riemann-Liouville fractional derivative of order α andlet u be a weight function defined on (0, b). For each fixed t ∈ (0, b), define afunction

p(t) :=f2(t)

Γ(−α)

∫ b

t

u(x)(x− t)−α−1 exp

(− rxt −

sx(x−t)

)Dαxf2(x); r, s

dx <∞.

If Φ : (0,∞)→ R is a convex and increasing function andDαxf1(x);r,s

Dαxf2(x);r,s ,

f1(t)f2(t) ∈

(0,∞), then the inequality

(3.8)

∫ b

0

u(x)Φ

(∣∣∣∣Dαxf1(x); r, s

Dαxf2(x); r, s

∣∣∣∣) dx ≤ ∫ b

0

p(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣) dtholds for all measurable functions fi ∈ L1(0, b), (i = 1, 2).

Proof. Applying Theorem 2.6 with Ω1 = Ω2 = (0, b), dµ1(x) = dx, dµ2(t) = dt,

g1(x) = Dαxf1(x); r, s, g2(x) = Dα

xf2(x); r, s and using k(x, t) provided in(3.5), we obtain inequality (3.8).

The upcoming result is the generalization of Theorem 3.4.

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ON SOME WEIGHTED HARDY-TYPE INEQUALITIES 167

Theorem 3.6. Let the assumption of Theorem 3.4 be satisfied, 0 < p ≤ q <∞and the weight function be defined by

w(t) =

∫ b

t

u(x)

(x− t)−α−1 exp(− rxt −

sx(x−t)

)x−αBr,s(1,−α)

qp

dx

pq

<∞.

If Φ is a non negative convex function on I ⊂ R, then the inequality

(3.9)

[∫ b

0

u(x)

(Γ(−α)Dα

xf(x); r, sx−αBr,s(1,−α)

)) qp

dx

] 1q

[∫ b

0

w(t)Φ(f(t))dt

] 1p

holds.

Proof. Applying Theorem 2.7 with Ω1 = Ω2 = (0, b), dµ1(x) = dx, dµ2(t) = dt,

K(x), k(x, t) and Akf(x) are given in (3.4), (3.5) and (3.7), respectively, weget inequality (3.9).

Theorem 3.7. Let R(r) > 0, R(s) > 0 and R(α) < 0. Let Dαxf(x); r, s

denote the extension of Riemann-Liouville fractional derivative of order α andDαxf2(x); r, s > 0 for every x ∈ (a, b). Let u be a weight function defined on

(a, b). For each fixed t ∈ (0, b), define a function

r(t) :=f2(t)

Γ(−α)

∫ b

t

u(x)(x− t)−α−1 exp

(− rxt −

sx(x−t)

)Dαxf2(x); r, s

dx <∞.

If Φ : (0,∞)×(0,∞)→ R is a convex and increasing function andDαxf1(x);r,s

Dαxf2(x);r,s ,

Dαxf3(x);r,s

Dαxf4(x);r,s ,

f1(t)f2(t) ∈ (0,∞), then the inequality

(3.10)

∫ b

0

u(x)Φ

(∣∣∣∣Dαxf1(x); r, s

Dαxf2(x); r, s

∣∣∣∣ , ∣∣∣∣Dαxf3(x); r, s

Dαxf2(x); r, s

∣∣∣∣) dx≤∫ b

0

r(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣ , ∣∣∣∣f3(t)

f2(t)

∣∣∣∣) dtholds for all measurable functions fi ∈ L1(0, b), (i = 1, 2, 3).

Proof. Applying Theorem 2.8 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dt,

k(x, t), is offered in (3.5), g1(x) = Dαxf1(x); r, s, g2(x) = Dα

xf2(x); r, s andg3(x) = Dα

xf3(x); r, s, we get inequality (3.10).

Remark 3.8. If we choose r = s in inequalities (3.6), (3.8), (3.9) and (3.10), weget the results for the extended Riemann-Liouville fractional derivative givenin (3.2).

Remark 3.9. If we choose r = s = 0 in inequalities (3.6), (3.8), (3.9) and (3.10),we get the results for the classical Riemann-Liouville fractional derivative.

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168 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

4. Weighted Hardy-type integral inequalities for extendedRiemann-Liouville fractional derivative

This section includes weighted Hardy-type integral inequalities for more gen-eral extended Riemann-Liouville fractional derivative given in [29] and is de-fined as follows:

Definition 4.1. Let R(µ) < 0, R(p) > 0 and R(α) > 0. Then the moregeneral extended Riemann-Liouville fractional derivative Dµ;α

x;p f of order α isgiven by

Dµ;αx;p f(x) =

1

Γ(−µ)

∫ x

0

f(t)(x− t)−µ−1Eα

(− px2

t(x− t)

)dt,(4.1)

where Eα is the Mittag-Leffler function was introduced and studied by Mittag-Leffler in the year (1903) and is given by

(4.2) Eα(z) =

∞∑k=0

zk

Γ(αk + 1), α ∈ C.

In particular if we choose α = 1 in (4.1), we get extended Riemann-Liouvillefractional derivative given by (3.2). Similarly, if α = 1, p = 0, it reduces toclassical Riemann-Liouville fractional derivative.

Lemma 4.2. Let R(µ) < 0, R(p) > 0 and R(α) > 0. Then the followingequation holds:

K(x) =x−µBαp (1,−µ)

Γ(−µ),(4.3)

where

Bαp (δ1, δ2) =

∫ 1

0

tδ1−1 (1− t)δ2−1Eα

(− p

t(1− t)

)dt, R(δ1), R(δ2) > 0

is the modified extension of beta function presented in [33].

Proof. Since

(4.4) k(x, t) =

1

Γ(−µ) (x− t)−µ−1Eα

(− px2

t(x−t)

), 0 ≤ t ≤ x ;

0, x < t ≤ b .Therefore

K(x) =1

Γ(−µ)

∫ x

0

(x− t)−µ−1Eα

(− px2

t(x− t)

)dt,

which can be written as

=x−µ−1

Γ(−µ)

∫ x

0

(1− t

x)−µ−1Eα

(− p

tx (1− t

x )

)dt.

By substituting tx = y and using the simple calculation, we arrive at (4.3).

Page 9: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

ON SOME WEIGHTED HARDY-TYPE INEQUALITIES 169

Theorem 4.3. Let R(µ) < 0, R(p) > 0 and R(α) > 0. Let Dµ;αx;p f denote the

extension of Riemann-Liouville fractional derivative of order α and let u be aweight function defined on (0, b). For each fixed t ∈ (0, b), define a function vby

v(t) =

∫ b

t

u(x)(x− t)−µ−1Eα

(− px2

t(x−t)

)x−µBαp (1,−µ)

dx <∞.

If Φ : (0,∞)→ R is a convex and increasing function, then the inequality

(4.5)

∫ b

0

u(x)Φ

(∣∣∣∣Γ(−µ)Dµ;αx;p f(x)

x−µBαp (1,−µ)

∣∣∣∣) dx ≤ ∫ b

0

v(t)Φ(|f(t)|)dt

holds for all measurable functions f ∈ L1(0, b).

Proof. Applying Theorem 2.5 with Ω1 = Ω2 = (0, b), dµ1(x) = dx, dµ2(t) = dt,

K(x), k(x, t) given in (4.3), (4.4), respectively and define

(4.6) Akf(x) =Γ(−µ)Dµ;α

x;p f(x)x−µBαp (1,−µ)

,

we get inequality (4.5).

Theorem 4.4. Let R(µ) < 0, R(p) > 0 and R(α) > 0. Let Dµ;αx;p f denote the

extension of Riemann-Liouville fractional derivative of order α and let u be aweight function defined on (0, b). For each fixed t ∈ (0, b), define a function

p(t) :=f2(t)

Γ(−µ)

∫ b

t

u(x)(x− t)−µ−1Eα

(− px2

t(x−t)

)Dµ,αx,p f2(x)

dx <∞.

If Φ : (0,∞) → R is a convex and increasing function andDµ,αx:p f1(x)

Dµ,αx:p f2(x) ,

f1(t)f2(t) ∈

(0,∞), then the inequality

(4.7)

∫ b

0

u(x)Φ

(∣∣∣∣Dµ,αx:p f1(x)

Dµ,αx:p f2(x)

∣∣∣∣) dx ≤ ∫ b

0

p(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣) dtholds for all measurable functions fi ∈ L1(0, b), (i = 1, 2).

Proof. Applying Theorem 2.6 with Ω1 = Ω2 = (0, b), dµ1(x) = dx, dµ2(t) = dt,

g1(x) = Dµ,αx:p f1(x), g2(x) = Dµ,α

x:p f2(x) and using k(x, t) provided in (4.4),we obtain inequality (4.7).

The upcoming result is the generalization of Theorem 4.3.

Theorem 4.5. Let the assumption of Theorem 4.3 be satisfied, 0 < r ≤ s <∞and the weight function be defined by

w(t) =

∫ b

t

u(x)

(x− t)−α−1Eα

(− px2

t(x−t)

)x−µBαp (1,−µ)

sr

dx

rs

<∞.

Page 10: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

170 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

If φ is a non-negative convex function on I ⊂ R, then the inequality

(4.8)

[∫ b

0

u(x)

(Γ(−µ)Dµ,α

x:p f(x)x−µBqp(1,−µ)

)) sr

dx

] 1s

[∫ b

0

w(t)Φ(f(t))dt

] 1r

holds.

Proof. Applying Theorem 2.7 with Ω1 = Ω2 = (0, b), dµ1(x) = dx, dµ2(t) = dt,

K(x), k(x, t) and Akf(x) are given in (4.3), (4.4) and (4.6), respectively, weget inequality (4.8).

Theorem 4.6. Let R(µ) < 0, R(p) > 0 and R(α) > 0. Let Dµ;αx;p f de-

note the extension of Riemann-Liouville fractional derivative of order α andDµ,αx:p f2(x) > 0 for every x ∈ (0, b). Let u be a weight function defined on

(o, b). For each fixed t ∈ (0, b), define a function

r(t) :=f2(t)

Γ(−µ)

∫ b

t

u(x)(x− t)−µ−1Eα

(− px2

t(x−t)

)Dµ,αx:p f2(x)

dx <∞.

If Φ : (0,∞) × (0,∞) → R is a convex and increasing function, then theinequality

(4.9)

∫ b

0

u(x)Φ

(∣∣∣∣Dµ,αx:p f1(x)

Dµ,αx:p f2(x)

∣∣∣∣ , ∣∣∣∣Dµ,αx:p f3(x)

Dµ,αx:p f2(x)

∣∣∣∣) dx≤∫ b

0

r(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣ , ∣∣∣∣f3(t)

f2(t)

∣∣∣∣) dtholds for all measurable functions fi ∈ L1(0, b), (i = 1, 2, 3).

Proof. Applying Theorem 2.8 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dt,

k(x, t), is offered in (4.4), g1(x) = Dµ,αx:p f1(x), g2(x) = Dµ,α

x:p f2(x) andg3(x) = Dµ,α

x:p f3(x), we get inequality (4.9).

Remark 4.7. If we choose α = 1 in inequalities (4.5), (4.7), (4.8) and (4.9), weget the results for the extended Riemann-Liouville fractional derivative givenin (3.2).

Remark 4.8. If we choose α = 1, p = 0 in inequalities (4.5), (4.7), (4.8) and(4.9), we get the results for the classical Riemann-Liouville fractional derivativeoperator.

5. Hardy-type inequalities for generalized fractional integraloperator involving Gauss hypergeometric function

This section deals with Hardy-type inequalities for generalized fractionalintegral operator involving Guass hypergeometric function in its kernel. Wefirst give the definition of generalized fractional integral operator offered in [8].

Page 11: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

ON SOME WEIGHTED HARDY-TYPE INEQUALITIES 171

Definition 5.1. Let α > 0, µ > −1, β, η ∈ R. Then the generalized fractionalintegral Iα,β,η,µa,x f of order α, for a real-valued continuous function f is definedby:

Iα,β,η,µa,x f(x) =x−α−β−2µ

Γ(α)

∫ x

a

tµ(x− t)α−1

× 2F1

(α+ β + µ,−η;α; 1− t

x

)f(t)dt, x ∈ [a, b],(5.1)

where the function 2F1(·, ·, ; ·) appearing in the kernel of above operator is theGaussian hypergeometric function defined by

2F1(a, b; c; t) =

∞∑n=0

(a)n(b)n(c)nn!

tn

and (a)n is the Pochhammer symbol defined as (a)n = a(a+ 1) · · · (a+ n− 1),(a)0 = 1. The operator (5.1) includes the Saigo, the Riemann-Liouville andthe Erdelyi-Kober fractional integral operators, i.e.,

Iα,β,η,0a,x f(x) =x−α−β

Γ(α)

∫ x

a

(x−t)α−12F1

(α+β−η;α; 1− t

x

)f(t)dt, x ∈ [a, b],

Rαf(x) = Iα,−α,η,0a,x f(x) =1

Γ(α)

∫ x

a

(x− t)α−1f(t)dt, x ∈ [a, b]

and

Iα,ηf(x) = Iα,0,η,0a,x f(x) =x−α−η

Γ(α)

∫ x

a

(x− t)α−1tηf(t)dt, x ∈ [a, b].

The upcoming lemma includes the calculation of K(x) given in (2.6) for thegeneralized integral operator (5.1), which we used to derive our main results ofthis section.

Lemma 5.2. Let α > 0, µ > −1, β, η ∈ R. Then the following relation exists:

(5.2) K(x) =x−µ−βΓ(µ+ 1)Γ(1− β + η)

Γ(1− β)Γ(α+ µ+ 1 + η).

Proof. Since

k(x, t) =

x−α−β−2µtµ(x−t)α−1

2F1(α+β+µ,−η;α;1− tx )

Γ(α) , 0 ≤ t ≤ x ;

0, x < t ≤ b ,(5.3)

so that

K(x) =

∫ x

0

x−α−β−2µ

Γ(α)2F1

(α+ β + µ,−η, α; 1− t

x

)tµ(x− t)α−1dt,

substituting 1− tx = y and using formula given in ([11], page 813), i.e.,∫ 1

0

xγ−1(1− x)ρ−12F1(α, β; γ;x)dx =

Γ(γ)Γ(ρ)Γ(γ + ρ− α− β)

Γ(γ + ρ− α)Γ(ρ+ γ − β),

Page 12: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

172 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

we get (5.2).

Our first main result is given in next theorem.

Theorem 5.3. Let α > 0, µ > −1, β, η ∈ R, Iα,β,η,µa,x f denote the general-ized fractional integral of order α and u be a weight function defined on (0, b).Moreover, for each fixed t ∈ (0, b), we define v by

v(t) =Γ(1− β)Γ(α+ µ+ 1 + η)

Γ(µ+ 1)Γ(1− β + η)

∫ b

t

u(x)x−α−µ

× 2F1

(α+ β + µ,−η, α; 1− t

x

)tµ(x− t)α−1dx.

If Φ : (0,∞)→ R is a convex and increasing function, then the inequality

(5.4)

∫ b

0

u(x)Φ

(∣∣∣∣ Γ(1− β)Γ(α+ µ+ 1 + η)

x−µ−βΓ(µ+ 1)Γ(1− β + η)Iα,β,η,µ0,x f(x)

∣∣∣∣) dx≤∫ b

0

v(t)Φ(|f(t)|)dt

holds for all measurable functions f ∈ L1(0, b).

Proof. Applying Theorem 2.5 with Ω1 = Ω2 = (0, b), dµ1(x) = dx, dµ2(t) = dt,

K(x), k(x, t) are given in (5.2), (5.3), respectively and define

(5.5) Akf(x) =Iα,β,η,µ0,x f(x)Γ(1− β)Γ(α+ µ+ 1 + η)

x−µ−βΓ(µ+ 1)Γ(1− β + η),

we get inequality (5.4).

Theorem 5.4. Let α > 0, µ > −1, β, η ∈ R, Iα,β,η,µa,x f denote the generalized

fractional integral of order α and Iα,β,η,µa,x f2(x) > 0. Define p on (a, b) by

p(t) :=f2(t)

Γ(α)

∫ b

t

u(x)x−α−β−2µ2F1(α+ β + µ,−η, α; 1− t

x )tµ(x− t)α−1

Iα,β,η,µa,x f2(x).

If Φ : (0,∞)→ R is a convex and increasing function andIα,β,η,µa,x f1(x)

Iα,β,η,µa,x f2(x), f1(t)f2(t) ∈

(0,∞), then the inequality

(5.6)

∫ b

a

u(x)Φ

(∣∣∣∣∣Iα,β,η,µa,x f1(x)

Iα,β,η,µa,x f2(x)

∣∣∣∣∣)dx ≤

∫ b

a

p(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣) dtholds for all measurable functions fi ∈ L1(a, b), (i = 1, 2).

Proof. Applying Theorem 2.6 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dt

and k(x, t) is given in (5.3), we get inequality (5.6).

Next theorem is the generalization of Theorem 5.3.

Page 13: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

ON SOME WEIGHTED HARDY-TYPE INEQUALITIES 173

Theorem 5.5. Let α > 0, µ > −1, β, η ∈ R and Iα,β,η,µa,x f denote thegeneralized fractional integral of order α and u be a weight function. Let0 < p ≤ q <∞ and

w(t) =Γ(1− β)Γ(α+ µ+ 1 + η)

Γ(µ+ 1)Γ(1− β + η)

×

(∫ b

t

u(x)

(x−α−µ2F1

(α+β+µ,−η, α; 1− t

x

)tµ(x−t)α−1

) qp

dx

) pq

.

If Φ is a non-negative convex function on the interval I ⊆ R, then the followinginequality [∫ b

0

u(x)

(Γ(1− β)Γ(α+ µ+ 1 + η)

x−µ−βΓ(µ+ 1)Γ(1− β + η)Iα,β,η,µ0,x f(x)

)) qp

dx

] 1q

[∫ b

0

w(t)Φ(f(t))dt

] 1p

(5.7)

holds true.

Proof. Applying Theorem 2.7 with Ω1 = Ω2 = (0, b), dµ1(x) = dx, dµ2(t) = dt,

K(x) k(x, t) and Akf(x) are provided in (5.2), (5.3) and (5.5), respectively, weget inequality (5.7).

Theorem 5.6. Let α > 0, µ > −1, β, η ∈ R, Iα,β,η,µa,x f denote the generalized

fractional integral of order α and Iα,β,η,µa,x f2(x) > 0 for every x ∈ (a, b). Let ube a weight function on (a, b). Then for each fixed t ∈ (a, b), we define r by

r(t) :=f2(t)

Γ(α)

∫ b

t

u(x)x−α−β−2µ

2F1(α+ β + µ,−η, α; 1− tx )tµ(x− t)α−1

Iα,β,η,µa,x f2(x)dx

< ∞.

If Φ : (0,∞) × (0,∞) → R is a convex and increasing function, then thefollowing inequality

(5.8)

∫ b

a

u(x)Φ

(∣∣∣∣∣ (Iα,β,η,µa,x f1)(x)

(Iα,β,η,µa,x f2(x)

∣∣∣∣∣ ,∣∣∣∣∣ (Iα,β,η,µa,x f3)(x)

(Iα,β,η,µa,x f2)(x)

∣∣∣∣∣)dx

≤∫ b

a

r(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣ , ∣∣∣∣f3(t)

f2(t)

∣∣∣∣) dtholds for all measurable functions fi ∈ L1(a, b), (i = 1, 2, 3).

Proof. Applying Theorem 2.8 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dt,

k(x, t) is offered in (5.3), we get inequality (5.8).

Remark 5.7. If we take µ = 0, in inequalities (5.4), (5.6), (5.7) and (5.8), weget the inequalities for the Saigo fractional integral.

Page 14: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

174 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

Remark 5.8. If along µ = 0, we take β = −α, in inequalities (5.4), (5.6), (5.7)and (5.8), we get the inequalities for the Riemann-Liouvill fractional integral.

Remark 5.9. If we take β = 0 and µ = 0, in inequalities (5.4), (5.6), (5.7) and(5.8), we get the inequalities for the Erdelyi-Kober fractional integral.

6. Hardy-type inequalities for generalized Riemann-Liouvillefractional integral operator

Let us recall the definition of generalized Riemann-Liouville fractional inte-gral operator specified in [21].

Definition 6.1. Let α > 0, a ≥ 0 and r 6= −1, a real number and let f ∈L1,r[a, b]. Then the generalized Riemann-Liouville fractional integral Iα,ra f isdefined by

(6.1) Iα,ra f(x) =(r + 1)1−α

Γ(α)

∫ x

a

(xr+1 − tr+1)α−1trf(t)dt, x ∈ (a, b).

We note that if r → −1+ the integral operator (6.1) reduces to the famousHadamard fractional integral:

(6.2) Iα,−1+

a f(x) =1

Γ(α)

∫ x

a

(log

x

t

)α−1 f(t)

tdt.

The first result for the generalized Riemann-Liouville fractional integral op-erator is as follows:

Theorem 6.2. Let f ∈ L1,r[a, b], α ≥ 0 and r 6= −1 and let u be a weight

function on (a, b). Assume that the function x 7→ u(x)α(r+1)(xr+1−tr+1)α−1tr

(xr+1−ar+1)α is

integrable on (a, b). Then for each fixed t ∈ (a, b), we define v by

v(t) := α(r + 1)

∫ b

t

u(x)(xr+1 − tr+1)α−1tr

(xr+1 − ar+1)αdx <∞.

If Φ : (0,∞)→ R is a convex and increasing function, then the inequality

(6.3)

∫ b

a

u(x)Φ

(∣∣∣∣ α(r + 1)

(xr+1 − ar+1)α

∫ x

a

(xr+1 − tr+1)α−1trf(t)dt

∣∣∣∣) dx≤∫ b

a

v(t)Φ(|f(t)|)dt

holds for all measurable functions f : (a, b)→ R.

Proof. Applying Theorem 2.5 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dt,

k(x, t) =

(r+1)1−α(xr+1−tr+1)α−1tr

Γ(α) , a ≤ t ≤ x ;

0, x < t ≤ b ,(6.4)

(6.5) K(x) =(xr+1 − ar+1)α

αΓ(α)(r + 1)α

Page 15: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

ON SOME WEIGHTED HARDY-TYPE INEQUALITIES 175

and

(6.6) Akf(x) =α(r + 1)

(xr+1 − ar+1)α

∫ x

a

(xr+1 − tr+1)α−1trf(t)dt,

we get inequality (6.3).

Remark 6.3. In particular if we choose r = 0 in inequality 6.3, we get [18,Corollary 2.2].

Corollary 6.4. In particular if r → −1 and a > 0 in Theorem 6.2, we get

s(t) :=α

t

∫ b

t

u(x)

(log x

t

)α−1(log x

a

)α dx

and the inequality (6.3) reduces to∫ b

a

u(x)Φ

(∣∣∣∣∣α∫ x

a

(log x

t

)α−1(log x

a

)α f(t)

tdt

∣∣∣∣∣)dx ≤

∫ b

a

s(t)Φ(|f(t)|)dt.

Corollary 6.5. In particular for the weight function u(x) = xr(xr+1−ar+1)α,x ∈ (a, b), in Theorem 6.2, we obtain v(t) = tr(br+1−tr+1)α, then the inequality(6.3) takes the form∫ b

a

xr(xr+1−ar+1)αΦ

(∣∣∣∣ α(r+1)

(xr+1−ar+1)α

∫ x

a

(xr+1−tr+1)α−1trf(t)dt

∣∣∣∣) dx≤∫ b

a

tr(br+1 − tr+1)αΦ(|f(t)|)dt.(6.7)

Although (6.3) holds for all convex and increasing functions, but we shall con-sider a power function which is of our interest. Let q > 1 and functionΦ : R→ R be define by Φ(x) = xq. Then (6.7) reduces to

(αΓ(α)(r + 1)α)q∫ b

a

xr(xr+1 − ar+1)α(1−q) |Iα,ra f(x)| dx

≤∫ b

a

tr(br+1 − tr+1

)α |f(t)|qdt.(6.8)

Since x ∈ (a, b) and α(1− q) < 0, then from the left hand side of (6.8), we canhave

(αΓ(α)(r + 1)α)q∫ b

a

xr(xr+1 − ar+1)α(1−q) |Iα,ra f(x)| dx

≥ (αΓ(α)(r + 1)α)qar(br+1 − ar+1)α(1−q)

∫ b

a

|Iα,ra f(x)|qdx(6.9)

and the right hand side of (6.8) can be estimated as

(6.10)

∫ b

a

tr(br+1 − tr+1)α|f(t)|qdt ≤ br(br+1 − ar+1)α∫ b

a

|f(t)|qdt.

Page 16: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

176 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

Combining (6.9) and (6.10), we get

(αΓ(α)(r + 1)α)qar(br+1 − ar+1)α(1−q)

∫ b

a

|Iα,ra f(x)|qdx

≤ br(br+1 − ar+1)α∫ b

a

|f(t)|qdt,

that is ∫ b

a

|Iα,ra f(x)|qdx ≤ br

ar

((br+1 − ar+1

)ααΓ(α)(r + 1)α

)q ∫ b

a

|f(t)|qdt.(6.11)

Taking power 1q on both sides of inequality (6.11), we can have

(6.12) ‖Iα,ra f‖q ≤M‖f‖q,where

M =

(b

a

) rq (br+1 − ar+1)α

Γ(α+ 1)(r + 1)α.

Remark 6.6. If in particular we choose r = 0 in inequality (6.12), we get[18, Remark 2.5].

Theorem 6.7. Let u be a weight function on (a, b), Iα,ra f be the generalizedRiemann-Liouville fractional integral of order α > 0, r 6= 0 and Iα,ra f2(x) > 0.

Assume that the function x 7→ u(x) f2(t)(xr+1−tr+1)α−1tr

Iα,ra f2(x)is integrable on (a, b).

Define p on (a, b) by

(6.13) p(t) :=(r + 1)1−αf2(t)

Γ(α)

∫ b

t

u(x)(xr+1 − tr+1)α−1tr

Iα,ra f2(x)dx <∞.

If Φ : (0,∞)→ R is a convex and increasing function, then the inequality∫ b

a

u(x)Φ

(∣∣∣∣Iα,ra f1(x)

Iα,ra f2(x)

∣∣∣∣) dx ≤ ∫ b

a

p(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣) dt(6.14)

holds for all measurable functions fi ∈ L1(a, b), (i = 1, 2).

Proof. Applying Theorem 2.6 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dtand k(x, t) is given by (6.4), we get inequality (6.14).

Corollary 6.8. For the particular choice of r → −1+, in Theorem 6.7 theweight function (6.13) becomes

q(t) :=f2(t)

tΓ(α)

∫ b

t

u(x)

(log x

t

)α−1

Iα,−1a f2(x)

dx <∞

and the inequality (6.14) takes the form∫ b

a

u(x)Φ

(∣∣∣∣Iα,−1a f1(x)

Iα,−1a f2(x)

∣∣∣∣) dx ≤ ∫ b

a

q(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣) dt,which is [19, Corollary 2.6].

Page 17: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

ON SOME WEIGHTED HARDY-TYPE INEQUALITIES 177

Next theorem is the generalized version of Theorem 6.2.

Theorem 6.9. Let 0 < p ≤ q < ∞ and f ∈ L1,r[a, b]. Let Iα,ra f denote thegeneralized Riemann-Liouville fractional integral of order α > 0 and r 6= −1.

Suppose u is a weight function and x 7→ u(x)(

(xr+1−tr+1)α−1tr

(xr+1−ar+1)α

) qp

is integrable

on (a, b). Then for each fixed t ∈ (a, b), the weight function w is defined by

(6.15) w(t) := α(r + 1)

[∫ b

t

u(x)

((xr+1 − tr+1)α−1tr

(xr+1 − ar+1)α

) qp

dx

] pq

<∞.

If Φ is a non-negative convex function on the interval I ⊆ R, then the inequality[∫ b

a

(αΓ(α)(r + 1)αIα,ra f(x)

(xr+1 − ar+1)α

)) qp

dx

] 1q

[∫ b

a

w(t)Φ (f(t)) dt

] 1p

(6.16)

holds for all measurable functions f : (a, b)→ R.

Proof. Applying Theorem 2.7 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dt,k(x, t), K(x) and Akf(x), are given by (6.4), (6.5) and (6.6), respectively, weget inequality (6.16).

The upcoming corollary is a special case of Theorem 6.9, which involveresults for the Hadamard fractional integral operator.

Corollary 6.10. In particular when r → −1+, then the weight function (6.15)can be written as:

h(t) := α

[∫ b

t

u(x)

((log x

t )α−1

t(log xa )α

) qp

dx

] pq

and the inequality (6.16) becomes[∫ b

a

(Γ(α+ 1)

(log xa )α

Iα,−1a f(x)

)) qp

dx

] 1q

[∫ b

a

h(t)(t)Φ (f(t)) dt

] 1p

.

Remark 6.11. If we choose r = 0 in inequality (6.16), we get [17, Corollary2.4].

Theorem 6.12. Let f ∈ L1,r[a, b], Iα,ra f be the generalized Riemann-Liouville

fractional integral of order α > 0, r 6= −1 and Iα,ra f2(x) > 0 for every x ∈ (a, b).Let u be a weight function on (a, b). Then r is defined by

(6.17) r(t) :=(r + 1)1−αf2(t)

Γ(α)

∫ b

t

u(x)(xr+1 − tr+1)α−1tr

Iα,ra f2(x)dx <∞.

If Φ : (0,∞) × (0,∞) → R is a convex and increasing function, then theinequality ∫ b

a

u(x)Φ

(∣∣∣∣ (Iα,ra f1)(x)

Iα,ra f2(x)

∣∣∣∣ , ∣∣∣∣ (Iα,ra f3)(x)

(Iα,ra f2)(x)

∣∣∣∣) dx(6.18)

Page 18: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

178 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

≤∫ b

a

r(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣ , ∣∣∣∣f3(t)

f2(t)

∣∣∣∣) dtholds for all measurable functions fi ∈ L1(a, b), (i = 1, 2, 3).

Proof. Applying Theorem 2.8 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dtand k(x, t) is given in (6.4), we get inequality (6.18).

As special case of Theorem 6.12, we next present the result for the Hadamardfractional integral operator.

Corollary 6.13. If we choose r → −1+, then the weight function (6.17) be-comes

f(t) :=f2(t)

Γ(α)

∫ b

t

u(x)(log x

t )α−1

tIα,−1a f2(x)

dx <∞

and the inequality (6.18) for the Hadamard fractional integral turn into∫ b

a

u(x)Φ

(∣∣∣∣ (Iα,−1a f1)(x)

Iα,−1a f2(x)

∣∣∣∣ , ∣∣∣∣ (Iα,−1a f3)(x)

(Iα,−1a f2)(x)

∣∣∣∣) dx≤∫ b

a

f(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣ , ∣∣∣∣f3(t)

f2(t)

∣∣∣∣) dt.7. Hardy-type inequalities for the Riemann-Liouville k-fractional

integral operator

The definition and notation of generalized Riemann-Liouville k-fractionalintegral operator presented in [27] is defined as follows:

Definition 7.1. Let f ∈ L1[a, b]. Then the Riemann-Liouville k-fractionalintegral Iαa,kf of order α > 0 and k > 0, is given by

(7.1) Iαa,kf(x) =1

kΓk(α)

∫ x

a

(x− t)αk−1f(t)dt, x ∈ (a, b),

where Γk is defined by (2.4). Moreover, if we choose k = 1, the integral operator(7.1) represents the left sided Riemann-Liouville fractional integral.

Theorem 7.2. Let f ∈ L1[a, b]. Then the Riemann-Liouville k-fractionalintegral Iαa,kf of order α > 0 and k > 0, is bounded, i.e.,

‖Iαa,kf‖q ≤ A‖f‖q,

where A = k1q−1

(b−a)αk

(qα)1q (Γk(α))(p(αk−

1q ))

1p

.

Proof. Since we have

|Iαa,kf(x)| ≤ 1

kΓk(α)

∫ x

a

|f(t)|(x− t)αk−1dt.

Page 19: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

ON SOME WEIGHTED HARDY-TYPE INEQUALITIES 179

Using Holder’s inequality on the right hand side of the above inequality, wehave

|Iαa,kf(x)| ≤ 1

kΓk(α)

(∫ x

a

(x− t)p(αk−1)dt

) 1p(∫ x

a

|f(t)|qdt) 1q

=(x− a)

αk−

1q

kΓk(α)(

(p(αk −1q ))) 1p

(∫ x

a

|f(t)|qdt) 1q

.

Consequently, we find

‖Iαa,kf(x)‖q ≤k

1q−1(b− a)

αk

(qα)1q (Γk(α))

(p(αk −

1q )) 1p

‖f(t)‖q.

This completes the proof.

Remark 7.3. If we take k = 1, in above result, we arrive at [18, Theorem 2.6].

Theorem 7.4. Let f ∈ L1[a, b], α > 0 and let u is a weight function, x 7→u(x)α(x−t)

αk

−1

k(x−a)αk

is integrable on (a, b). Then for each fixed t ∈ (a, b), we define

a function v by

v(t) :=α

k

∫ b

t

u(x)(x− t)αk−1

(x− a)αk

dx <∞.

If Φ : (0,∞)→ R is a convex and increasing function, then the inequality

(7.2)

∫ b

a

u(x)Φ

(∣∣∣∣ α

k(x− a)αk

∫ x

a

(x− t)αk−1f(t)dt

∣∣∣∣) dx ≤ ∫ b

a

v(t)Φ(|f(t)|)dt

holds for all measurable functions f : (a, b)→ R.

Proof. Applying Theorem 2.5 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dt,

k(x, t) =

(x−t)

αk

−1

kΓk(α) , a ≤ t ≤ x ;

0, x < t ≤ b ,(7.3)

K(x) is defined by

(7.4) K(x) =1

αΓk(α)(x− a)

ak

and

(7.5) Akf(x) =α

k(x− a)αk

∫ x

a

(x− t) ak−1f(t)dt,

we get inequality (7.2).

Page 20: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

180 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

Corollary 7.5. Let Iαa,kf be the Riemann-Liouville k-fractional integral of

order α > 0 and k > 0. Choose a particular weight function u(x) = (x− a)αk ,

x ∈ (a, b) in Theorem 7.4, we obtain v(t) = (b− t)αk . Then the inequality (7.2)takes the form∫ b

a

(x− a)αk Φ

(∣∣∣∣ α

k(x− a)αk

∫ x

a

(x− t)αk−1f(t)dt

∣∣∣∣) dx≤∫ b

a

(b− t)αk Φ(|f(t)|)dt.(7.6)

Let q > 1 and function Φ : (0,∞) → R be define by Φ(x) = xq. Then (7.6)becomes ∫ b

a

(x− a)αk

(αΓk(α)|Iαa,kf(x)|

(x− a)αk

)qdx ≤

∫ b

a

(b− t)αk |f(t)|qdt.

Since x ∈ (a, b) and αk (1− q) < 0, then after some calculations, we have

‖Iαa,k‖q ≤ N‖f‖q,where

N =(b− a)

αk

αΓk(α).

Remark 7.6. Particularly for k = 1, we get [18, Remark 2.3].

Theorem 7.7. Let u be a weight function on (a, b), Iαa,kf be the Riemann-

Liouville k-fractional integral of order α > 0 and Iαa,kf2(x) > 0 for every x ∈

(a, b). Assume that the function x 7→ u(x) f2(t)(x−t)αk

−1

kΓk(α)Iαa,kf2(x) is integrable on (a, b).

Then define p on (a, b) by

p(t) :=f2(t)

kΓk(α)

∫ b

t

u(x)(x− t)αk−1

Iαa,kf2(x)dx <∞.

If Φ : (0,∞)→ R is a convex and increasing function, then the inequality∫ b

a

u(x)Φ

(∣∣∣∣∣Iαa,kf1(x)

Iαa,kf2(x)

∣∣∣∣∣)dx ≤

∫ b

a

p(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣) dt(7.7)

holds for all measurable functions fi ∈ L1(a, b), (i = 1, 2).

Proof. Applying Theorem 2.6 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dt

and k(x, t), is given in (7.3), we get inequality (7.7).

Theorem 7.8. Let α > 0, 0 < p ≤ q < ∞, f ∈ L1[a, b], let u be a weight

function on (a, b) and x 7→ u(x)(

(x−t)αk

−1

(x−a)αk

) qp

is integrable on (a, b). Then for

each fixed t ∈ (a, b), w is defined by

w(t) :=α

k

[∫ b

t

u(x)

((x− t)αk−1

(x− a)αk

) qp

dx

] pq

<∞.

Page 21: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

ON SOME WEIGHTED HARDY-TYPE INEQUALITIES 181

If Φ is a non-negative convex function on the interval I ⊆ R, then the inequality[∫ b

a

u(x)

k(x− a)αk

∫ x

a

(x− t)αk−1f(t)dt

)) qp

dx

] 1q

[∫ b

a

w(t)Φ (f(t)) dt

] 1p

(7.8)

holds for all measurable functions f : (a, b)→ R such that Imf ⊆ I.

Proof. Applying Theorem 2.7 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dt,

k(x, t), K(x) and Akf(x) are given by (7.3), (7.4) and (7.5), respectively, weget inequality (7.8).

Corollary 7.9. Let 0 < p ≤ q < ∞, f ∈ L1[a, b] and Iαa,kf be the Riemann-

Liouville k-fractional integral of order α > 0. Suppose Φ(x) = xs, s > 0, is a

convex function and u(x) = (x − a)qαpk a particular weight function. Then for

each fixed t ∈ (a, b), g(t) is defined by

g(t) =α

k(qp (αk − 1) + 1

) pq

(b− t)αk−1+ p

q .

Substituting these values in (7.8) and after some calculations we get the in-equality(∫ b

a

(Iαa,kf(x)

) qsp dx

) 1q

≤ (α)1p (b−a)

αspk+

1q−

1p

(k(Γk(α+k))s)1p

(qp (αk−1)+1

) 1q

(∫ b

a

fs(t)dt

) 1p

.

Theorem 7.10. Let Iαa,kf be the Riemann-Liouville k-fractional integral of

order α > 0 and let Iαa,kf2(x) > 0 for every x ∈ (a, b), u is a weight function

on (a, b). Then r is defined by

r(t) :=f2(t)

kΓk(α)

∫ b

t

u(x)(x− t)αk−1

Iαa,kf2(x)dx <∞.

If Φ : (0,∞) × (0,∞) → R is a convex and increasing function, then theinequality

(7.9)

∫ b

a

u(x)Φ

(∣∣∣∣∣Iαa,kf1(x)

Iαa,kf2(x)

∣∣∣∣∣ ,∣∣∣∣∣Iαa,kf3(x)

Iαa,kf2(x)

∣∣∣∣∣)dx ≤

∫ b

a

r(t)Φ

(∣∣∣∣f1(t)

f2(t)

∣∣∣∣ , ∣∣∣∣f3(t)

f2(t)

∣∣∣∣) dtholds for measurable functions fi ∈ L1(a, b), (i = 1, 2, 3).

Proof. Applying Theorem 2.8 with Ω1 = Ω2 = (a, b), dµ1(x) = dx, dµ2(t) = dt

and k(x, t), is given by (7.3), we get inequality (7.9).

Remark 7.11. If we choose k = 1, in inequalities (7.2), (7.7), (7.8) and (7.9),we get results for the Riemann-Liouville fractional integral operator.

Page 22: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

182 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

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Sajid IqbalDepartment of Mathematics

University of Sargodha (Sub-Campus Bhakkar)

Bhakkar, PakistanEmail address: sajid [email protected]

Josip PecaricRUDN University

Moscow, Russia

Email address: [email protected]

Muhammad Samraiz

Department of MathematicsUniversity of Sargodha

Sargodha, Pakistan

Email address: [email protected]; [email protected]

Hassan Tehmeena

Department of MathematicsUniversity of Sargodha (Mandi Bahauddin Campus)

Mandi Bahauddin, Pakistan

Email address: [email protected]

Page 24: Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan … · Sajid Iqbal, Josip Pe cari c, Muhammad Samraiz, Hassan Tehmeena, and Zivorad Tomovski Abstract. In this article, we establish

184 S. IQBAL, J. PECARIC, M. SAMRAIZ, H. TEHMEENA, AND Z. TOMOVSKI

Zivorad Tomovski

University St. cyril and Methodius

Faculty of Natural Sciences and MathematicsInstitute of Mathematics

Republic of MacedoniaEmail address: [email protected]