Katugampola fractional operators

In mathematics, Katugampola fractional operators are integral operators that generalize the Riemann–Liouville and the Hadamard fractional operators into a unique form. The Katugampola fractional integral generalizes both the Riemann–Liouville fractional integral and the Hadamard fractional integral into a single form and It is also closely related to the Erdelyi–Kober operator that genaralizes the Riemann–Liouville fractional integral. Katugampola fractional derivative has been defined using the Katugampola fractional integral and as with any other fractional differential operator, it also extends the possibility of taking real number powers or complex number powers of the integral and differential operators.

Definitions

These operators have been defined on the following extended-Lebesgue space.

Let $\textit{X}^p_c(a,b), \; c\in \mathbb{R}, \, 1 \leq p \leq \infty$ be the space of those Lebesgue measurable functions $f$ on $[a, b]$ for which $\|f\|_{\textit{X}^p_c} < \infty$, where the norm is defined by  

Failed to parse (Missing <code>texvc</code> executable. Please see math/README to configure.): \begin{align} \|f\|_{\textit{X}^p_c} =\Big(\int^b_a |t^c f(t)|^p \frac{dt}{t}\Big)^{1/p} < \infty, \end{align}

  for $1 \leq p < \infty,\, c \in \mathbb{R}$ and for the case $p=\infty$  

Failed to parse (Missing <code>texvc</code> executable. Please see math/README to configure.): \begin{align} \|f\|_{\textit{X}^\infty_c} = \text{ess sup}_{a \leq t \leq b} [t^c|f(t)|], \quad ( c \in \mathbb{R}). \end{align}

Katugampola fractional integral

It is defined via the following integrals

$({}^\rho \mathcal{I}^\alpha_{a+}f)(x) = \frac{\rho^{1- \alpha }}{\Gamma(\alpha)} \int^x_a \frac{\tau^{\rho-1} f(\tau) }{(x^\rho - \tau^\rho)^{1-\alpha}}\, d\tau,$

(1)

  for $x > a$ and $\operatorname{Re}(\alpha) > 0.$ This integral is called the left-sided fractional integral. Similarly, the right-sided fractional integral is defined by,  

$({}^\rho \mathcal{I}^\alpha_{b-}f)(x) = \frac{\rho^{1- \alpha }}{\Gamma({\alpha})} \int^b_x \frac{\tau^{\rho-1} f(\tau) }{(\tau^\rho - x^\rho)^{1-\alpha}}\, d\tau.$

(2)

  for Failed to parse (Missing <code>texvc</code> executable. Please see math/README to configure.): \textstyle x < b

and Failed to parse (Missing <code>texvc</code> executable. Please see math/README to configure.): \textstyle\operatorname{Re}(\alpha) > 0

.

These are the fractional generalizations of the $n$-fold left- and right-integrals of the form

$\int_a^x t_1^{\rho-1} \, dt_1 \int_a^{t_1} t_2^{\rho-1} \,dt_2 \cdots \int_a^{t_{n -1}} t_n^{\rho-1} f(t_n)\,dt_n$

and

$\int_x^b t_1^{\rho-1} \,dt_1 \int^b_{t_1} t_2^{\rho-1} \,dt_2 \cdots \int^b_{t_{n -1}} t_n^{\rho-1} f(t_n) \, dt_n$ for Failed to parse (Missing <code>texvc</code> executable. Please see math/README to configure.): \textstyle n \in \mathbb{N},

respectively. Even though the integral operators in question are close resemblance of the famous Erdélyi–Kober operator, it is not possible to obtain the Hadamard fractional integrals as a direct consequence of the Erdélyi–Kober operators. Also, there is a corresponding fractional derivative, which generalizes the Riemann–Liouville and the Hadamard fractional derivatives. As with the case of fractional integrals, the same is not true for the Erdélyi–Kober operator.

Katugampola fractional derivative

As with the case of other fractional derivatives, it is defined via the Katugampola fractional integral.

Let $\alpha \in \mathbb{C},\ \operatorname{Re}(\alpha) \geq 0, n=[\operatorname{Re}(\alpha)]+1$ and $\rho >0.$ The generalized fractional derivatives, corresponding to the generalized fractional integrals (1) and (2) are defined, respectively, for $0 \leq a < x < b \leq \infty$, by

Failed to parse (Missing <code>texvc</code> executable. Please see math/README to configure.): \begin{align} \big({}^\rho \mathcal{D}^\alpha_{a+}f\big)(x)&= \bigg(x^{1-\rho} \,\frac{d}{dx}\bigg)^n\,\, \big({}^\rho \mathcal{I}^{n-\alpha}_{a+}f\big)(x)\\ &= \frac{\rho^{\alpha-n+1 }}{\Gamma({n-\alpha})} \, \bigg(x^{1-\rho} \,\frac{d}{dx}\bigg)^n \int^x_a \frac{\tau^{\rho-1} f(\tau) }{(x^\rho - \tau^\rho)^{\alpha-n+1}}\, d\tau, \end{align}

and

Failed to parse (Missing <code>texvc</code> executable. Please see math/README to configure.): \begin{align} \big({}^\rho \mathcal{D}^\alpha_{b-}f\big)(x) &= \bigg(-x^{1-\rho} \,\frac{d}{dx}\bigg)^n\,\, \big({}^\rho \mathcal{I}^{n-\alpha}_{b-}f\big)(x)\\ &= \frac{\rho^{\alpha-n+1 }}{\Gamma({n-\alpha})}\bigg(-x^{1-\rho}\frac{d}{dx}\bigg)^n \int^b_x\frac{\tau^{\rho-1} f(\tau) }{(\tau^\rho - x^\rho)^{\alpha-n+1}}\, d\tau, \end{align}

respectively, if the integrals exist.

It is interesting to note that these operators generalize the Riemann–Liouville and Hadamard fractional derivatives into a single form, while the Erdelyi–Kober fractional is a generalization of the Riemann–Liouville fractional derivative. When, $b=\infty$, the fractional derivatives are referred to as Weyl-type derivatives.

Caputo–Katugampola fractional derivative

There is a Caputo-type modification of the Katugampola derivative that is now known as the Caputo–Katugampola fractional derivative.

These operators have been mentioned in the following works:

1. Fractional Calculus. An Introduction for Physicists, by Richard Herrmann
2. Fractional Calculus of Variations in Terms of a Generalized Fractional Integral with Applications to Physics, Tatiana Odzijewicz, Agnieszka B. Malinowska and Delfim F. M. Torres, Abstract and Applied Analysis, Vol 2012 (2012), Article ID 871912, 24 pages
3. Introduction to the Fractional Calculus of Variations, Agnieszka B Malinowska and Delfim F. M. Torres, Imperial College Press, 2015
4. Advanced Methods in the Fractional Calculus of Variations, Malinowska, Agnieszka B., Odzijewicz, Tatiana, Torres, Delfim F.M., Springer, 2015
5. Expansion formulas in terms of integer-order derivatives for the Hadamard fractional integral and derivative, Shakoor Pooseh, Ricardo Almeida, and Delfim F. M. Torres, Numerical Functional Analysis and Optimization, Vol 33, Issue 3, 2012, pp 301–319.

Mellin transform

As in the case of Laplace transforms, Mellin transforms will be used specially when solving differential equations. The Mellin transforms of the left-sided and right-sided versions of Katugampola Integral operators are given by

Theorem

Let $\alpha \in \mathcal{C},\ \operatorname{Re}(\alpha) > 0,$ and $\rho >0.$ Then,

Failed to parse (Missing <code>texvc</code> executable. Please see math/README to configure.): \begin{align} & \mathcal{M}\bigg({}^\rho \mathcal{I}^\alpha_{a+}f\bigg)(s) = \frac{\Gamma\big(1-\frac{s}{\rho}-\alpha\big)}{\Gamma\big(1-\frac{s}{\rho}\big)\,\rho^\alpha}\, \mathcal{M}f(s + \alpha\rho), \quad \operatorname{Re}(s/\rho + \alpha) < 1, \, x > a, \\ & \mathcal{M}\bigg({}^\rho \mathcal{I}^\alpha_{b-}f\bigg)(s) = \frac{\Gamma\big(\frac{s}{\rho}\big)}{\Gamma\big(\frac{s}{\rho} + \alpha\big)\,\rho^\alpha}\, \mathcal{M}f(s + \alpha\rho), \quad \operatorname{Re}(s/\rho) > 0, \, x < b, \\ \end{align}

for $f \in \textit{X}^1_{s + \alpha\rho}(\mathbb{R^+})$, if $\mathcal{M}f(s + \alpha\rho)$ exists for $s\in \mathbb{C}$.

Hermite-Hadamard type inequalities

Katugampola operators satisfy the following Hermite-Hadamard type inequalities:

Theorem

Let $\alpha > 0$ and $\rho >0.$. If $f$ is a convex function on $[a, b]$, then

$f\left(\frac{a+b}{2}\right) \leq \frac{\rho^\alpha\Gamma(\alpha +1)}{4(b^\alpha -a^\alpha)^\alpha}\left[{}^\rho \mathcal{I}^\alpha_{a+}F(b)+{}^\rho \mathcal{I}^\alpha_{b-}F(a)\right] \leq \frac{f(a)+f(b)}{2},$

where $F(x) = f(x) + f(a+b-x), \; x \in [a, b].$.

When $\rho \rightarrow 0^+$, in the above result, the following Hadamard type inequality holds:

Corollary

Let $\alpha > 0$. If $f$ is a convex function on $[a, b]$, then

$f\left(\frac{a+b}{2}\right) \leq \frac{\Gamma(\alpha +1)}{4\left(\ln \frac{b}{a}\right)^\alpha}\left[ \mathbf{I}^\alpha_{a+}F(b)+ \mathbf{I}^\alpha_{b-}F(a)\right] \leq \frac{f(a)+f(b)}{2},$

where $\mathbf{I}^\alpha_{a+}$ and $\mathbf{I}^\alpha_{b-}$ are left- and right-sided Hadamard fractional integrals.

Further reading

• An Introduction to the Fractional Calculus and Fractional Differential Equations, by Kenneth S. Miller, Bertram Ross (Editor). Hardcover: 384 pages. Publisher: John Wiley & Sons; 1 edition (May 19, 1993). ISBN 0-471-58884-9
• The Fractional Calculus; Theory and Applications of Differentiation and Integration to Arbitrary Order (Mathematics in Science and Engineering, V), by Keith B. Oldham, Jerome Spanier. Hardcover. Publisher: Academic Press; (November 1974). ISBN 0-12-525550-0
• Fractional Differential Equations. An Introduction to Fractional Derivatives, Fractional Differential Equations, Some Methods of Their Solution and Some of Their Applications., (Mathematics in Science and Engineering, vol. 198), by Igor Podlubny. Hardcover. Publisher: Academic Press; (October 1998) ISBN 0-12-558840-2
• Fractional Calculus. An Introduction for Physicists, by Richard Herrmann. Hardcover. Publisher: World Scientific, Singapore; (February 2011) ISBN 978-981-4340-24-3
• Recent history of fractional calculus by J.T. Machado, V. Kiryakova, F. Mainardi,

Notes

The CRONE (R) Toolbox, a Matlab and Simulink Toolbox dedicated to fractional calculus, can be downloaded at http://cronetoolbox.ims-bordeaux.fr