Generalizations of Hermite-Hadamard-Fejer Type Inequalities for Functions Whose Derivatives are s-Co...

ERHAN SET, IMDAT ISCAN, ILKER MUMCU

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Generalizations of Hermite-Hadamard-Fejer Type Inequalities for Functions Whose Derivatives are s-Convex Via Fractional Integrals

ERHAN SET1,, IMDAT ISCAN2, ILKER MUMCU1

1Department of Mathematics, Faculty of Arts and Sciences, Ordu University, Ordu, Turkey

2Department of Mathematics, Faculty of Arts and Sciences, Giresun University, Giresun, Turkey

Abstract

In this work, the new results related to right hand side of Hermite-Hadamard-Fejer inequality for s-convex functions in the second sense via fractionals integrals are obtained. This results are generalization of the results obtained by Işcan in [17].

Cite this article:

  • SET, ERHAN, IMDAT ISCAN, and ILKER MUMCU. "Generalizations of Hermite-Hadamard-Fejer Type Inequalities for Functions Whose Derivatives are s-Convex Via Fractional Integrals." Turkish Journal of Analysis and Number Theory 2.5 (2014): 183-188.
  • SET, E. , ISCAN, I. , & MUMCU, I. (2014). Generalizations of Hermite-Hadamard-Fejer Type Inequalities for Functions Whose Derivatives are s-Convex Via Fractional Integrals. Turkish Journal of Analysis and Number Theory, 2(5), 183-188.
  • SET, ERHAN, IMDAT ISCAN, and ILKER MUMCU. "Generalizations of Hermite-Hadamard-Fejer Type Inequalities for Functions Whose Derivatives are s-Convex Via Fractional Integrals." Turkish Journal of Analysis and Number Theory 2, no. 5 (2014): 183-188.

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1. Introduction

A function is said to be convex function if the inequality

(1.1)

holds for all x,y∈[a,b] and t∈[0,1].

One of the most famous inequality for convex functions is so called Hermite-Hadamard’s inequality as follows: Let be a convex function defined on the interval I of real numbers and a.b∈I with a < b. Then:

(1.2)

Fejér [22] gave a generalization of the inequalities (1.2) as the following:

If is a convex function, and is nonnegative, integrable and symmetric to then

(1.3)

For some results which generalize, improve, and extend the inequalities (1.3), see ([16-21][16]).

In [23], Hudzik and Maligrada considered among others the class of functions which are s-convex in the second sense.

Definition 1. A function is said to be s-convex in the second sense if

(1.4)

for all x,y∈[0,∞), ∈[0,1] and for some fixed s ∈(0,1].

It can be easily seen that s = 1, s-convexity reduces to ordinary convexity of functions defined on [0,∞).

In [24], Dragomir and Fitzpatrick proved Hermite-Hadamard’s inequality which holds for s-convex functions in the second sense.

Theorem 1. Suppose that f: [0,)[0,) is an s-convex functions in the second sense, where s (0,1), and let a, b[0,), a < b. If fL[a,b], then the following inequalities hold:

(1.5)

We give some necessary definitions and mathematical preliminaries of fractional calculus theory which are used throught this paper.

Definition 2. Let f[a,b]. The Riemann-Liouville integrals and of order α > 0 with a 0 are defined by

(1.6)

and

respectively where . Here is .

In the case of α= 1, the fractional integral reduces to the classical integral.

Let us consider the following special functions:

(1) The Beta function:

(2) The incomplete Beta function:

In [13], Sarikaya et. al. represented Hermite-Hadamard’s inequality in fractional integral forms as follows.

Theorem 2. Let be positive function with 0 a < b and f L[a,b].

If f is a convex function on [a,b], then the following inequalities for fractional integrals hold

(1.7)

with α > 0.

In [13], Sarikaya et. al. proved the following lemma.

Lemma 1. Let be a differentiable mapping on (a,b) with a < b. If f L[a,b] then the following equality for fractional integrals holds:

The following Hermite-Hadamard type inequality was proved using the above lemma.

Theorem 3. [13] Let be a differentiable mapping on (a,b) with a < b. If |f| is convex on [a,b] then the following inequality for fractional integrals holds:

Properties concerning this operator and more and more Hermite-Hadamard type inequalities involving fractional integrals for different classes of functions can be found ([1-15][1]).

Now, let us give the following lemma which we will use the proof.

Lemma 2. For 0 < α 1 and 0 a < b, we have

Işcan [17] established following lemmas and theorems connected with the right-hand side of Hermite-Hadamard-Fejer type integral inequality for the fractional integrals.

Lemma 3. If is integrable and symmetric to with a < b, then

with α > 0.

Theorem 4. Let be convex function with a < b and fL[a,b]. If is nonnegative, integrable and symmetric to (a + b)/2, then the following inequalities for fractional integrals hold

with α > 0.

Lemma 4. Let be a differentiable mapping on (a,b) with a < b and fL[a,b]. If is integrable and symmetric to (a + b)/2 then the following equality for fractional integral holds

with α > 0.

Theorem 5. Let be a differentiable mapping on and fL[a,b] with a < b. If |f| is convex on [a,b] and is continuous and symmetric to (a + b)/2, then the following inequality for fractional integral holds

(1.8)

with α > 0.

Theorem 6. Let be a differentiable mapping on and f L[a,b] with a < b: If |f|q, q > 1, is convex on [a,b] and is continuous and symmetric to (a + b)/2, then the following inequality for fractional integral holds

(1.9)

where α > 0 and .

Theorem 7. Let be a differentiable mapping on and f L[a,b] with a < b. If |f|q, q > 1, is convex on [a,b] and is continuous and symmetric to (a + b)/2, then the following inequality for fractional integral holds

(i)

(1.10)

with α> 0.

(ii)

(1.11)

for 0 < α 1 where .

The main of this paper is to establish some new inequalities related to the left-hand side of the Hermete-Hadamard-Fejer type inequalities for s-convex functions in the second sense via Riemann-Liouville fractional integrals.

2. Main Results

Theorem 8. Let be a differentiable mapping on and fL[a,b] with a < b. If |f| is s-convex on [a,b] for some fixed s (0,1], and is continious and symmetric to (a + b)/2, then the following inequality for fractional integral holds

(2.1)

with α > 0.

Proof. From Lemma 4 we have

(2.2)

Since |f’| is s-convex on [a,b] for some fixed s∈(0,1], we know that for t ∈[a,b]

(2.3)

and since is symmetric to (a + b)/2 we write

then we have

(2.4)

By virtue of (2.2), (2.3) and (2.4), we get

where

(2.5)

and

(2.6)

Remark 1. In Theorem 8, if we take s = 1, then the inequality (2.1) becomes inequality (1.8) of Theorem 5.

Theorem 9. Let be a differentiable mapping on Io and f L[a,b] with a < b. If |f|q, q > 1, is s-convex on [a,b] for some fixed s(0,1], and is continious and symmetric to (a + b)/2, then the following inequality for fractional integral holds

(2.7)

where α > 0.

Proof. Using Lemma 4, Hölder’s inequality, (2.4) and the s-convexity of |f’|q, it follows that

(2.8)

where it is easily seen that

Hence, if we use (2.5) and (2.6) in (2.8), we have

Remark 2. In Theorem 9, if we take s = 1, then the inequality (2.7) becomes inequality (1.9) of Theorem 6.

Theorem 10. Let be a differentiable mapping on and f L[a,b] with a < b. If |f|q, q > 1, is s-convex on [a,b] for some fixed s(0,1], and is continious and symmetric to (a + b)/2, then the following inequality for fractional integral holds

(i)

(2.9)

with α>0.

(ii)

(2.10)

for 0 < α < 1, where .

Proof. (i) Using Lemma 4, Hölder’s inequality, the inequality (2.4) and the s-convexity of |f’|q, it follows that

Here we use

for t ∈[0,1/2] and

for t ∈[1/2,1], which follows from

for any A ≥ B ≥ 0 and q ≥ 1. Hence the inequality (2.9) is proved.

(ii) The inequality (2.10) is easily proved using (2.11) and Lemma 2.

Remark 3. In Theorem 10, if we take s = 1, then inequalities (2.9) and (2.10) becomes inequalities (1.10) and (1.11) of Theorem 7.

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