Abstract and Applied Analysis

Volume 2014, Article ID 312578, 8 pages

http://dx.doi.org/10.1155/2014/312578

## A -Dimensional System of Fractional Finite Difference Equations

^{1}Department of Chemical and Materials Engineering, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia^{2}Department of Mathematics, Cankaya University, Ogretmenler Caddesi 14 Balgat 06530, Ankara, Turkey^{3}Institute of Space Sciences, Magurele, 76900 Bucharest, Romania^{4}Department of Mathematics, Azarbaijan Shahid Madani University, Azarshahr, Tabriz, Iran

Received 3 February 2014; Revised 13 March 2014; Accepted 13 March 2014; Published 9 April 2014

Academic Editor: Bashir Ahmad

Copyright © 2014 Dumitru Baleanu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

We investigate the existence of solutions for a -dimensional system of fractional finite difference equations by using the Kranoselskii’s fixed point theorem. We present an example in order to illustrate our results.

#### 1. Introduction

The fractional calculus revealed during the last decade its huge potential applications in many branches of science and engineering (see, e.g., [1–9]). A new and promising direction within fractional calculus is the discrete fractional calculus (see [6, 7, 10–14]). The advantages of this type of calculus are that it treats better phenomena with memory effect (see [10, 11, 14]). We recall that some researchers have been investigating discrete fractional calculus for special equations via very definite boundary conditions (see, e.g., [12, 13, 15–24] and the references therein). Many researchers could focus on this field by considering natural potential of fractional finite difference equations. In this paper, we investigate the existence of solutions for -dimensional system of fractional finite difference equations: where , , and are continuous functions for . One-dimensional version of the problem has been studied by Goodrich [18]. Also, Pan et al. studied two-dimensional version of the problem [24]. We show that the problem (1) is equivalent to a summation equation and by using Krasnoselskii's fixed point theorem we investigate solutions of the problem. In this way, we present an example to illustrate our result.

#### 2. Preliminaries

It is known that the finite fractional difference theory is important in many branches of science and engineering (see, e.g., [13, 16, 18, 19, 21, 25, 26] and the references therein). The Gamma function is defined by for the complex numbers in which the real part of is positive (see [8]). Note that the domain of the Gamma function is (see [8]). Now, we recall for all whenever the right-hand side is defined (see [16]). If is a pole of the Gamma function and is not a pole, then (see [16]). We recall that (see [16]). One can verify that and .

In this paper, we use the standard notations for all and for all real numbers and whenever is a natural number. Let with for some natural number . Then, the th fractional sum of based at is defined by for all , where is the forward jump operator (see [16]). Similarly, we define for all . Note that the domain of is for and for (see [16]). Also, for the natural number , we have to recall the formula We define the trivial sum for all .

Lemma 1 (see [13]). *Let be a mapping and a natural number. Then, the general solution of the equation is given by for all , where are arbitrary constants.*

Let be a mapping and a natural number. By using a similar proof, one can check that the general solution of the equation is given by for all . In particular, the general solution has the following representation: for all . By considering the details, note that whenever . Also for with and , the domain of the operator is given by , , , , , and (for more details see [13, 21, 22]). One can find next result about composing a difference with a sum in [12].

Lemma 2. *Let be a map, , and with . Then for all and for all .*

By using Lemma 1 and last lemma for , we get We are going to use this in our main results. A nonempty, closed subset of a topological vector space is called a cone whenever and for all and nonnegative real numbers (for more details and examples see [27] and references therein).

Lemma 3 (see [28]). *Let be a Banach space and a cone in . Assume that and are open subsets of such that and . Suppose that is a completely continuous operator. If either for all and for all or for all and for all , then has at least one fixed point in .*

#### 3. Main Result

In this section we provide the main results. For next result, consider the problem (1).

Lemma 4. *The fractional finite difference equation
**
via the boundary conditions has a solution if and only if is a solution of the summation equation , where the Green function is given by
**
for all . Here, and is one of equations of the system.*

*Proof. *Let and letbe a solution of the fractional finite difference equation , . By using Lemma 1, we get . By using the boundary condition , we obtain
and so . Now by using the boundary condition , we get
Hence, and so
Now, let be a solution of the fractional sum equation
Then, . Since , we get . Also,
Hence, we get
Moreover, . Since and , we get
This completes the proof.

Hereafter, for simplicity we use the notations and for all .

Lemma 5 (see [18]). *The Green function (7) satisfies for all and and for all and there exist such that
**
for all .*

Goodrich showed that (see [18]), where and Note that can be written in the simple form , becauseNote that hold because . Suppose that is the Banach space of the maps via the usual maximum norm . Consider the space via the norm . It is clear that is a Banach space (see [29]). Now, define the map by where for . Also, consider the cone defined by where . First, for the operator we show that whenever the functions are nonnegative for . Let . Then, we have where . Hence, and so . For providing our main result, we use similar conditions which have been given by Goodrich in [18] and Henderson et al. in [30].

Theorem 6. *Suppose that for all :
**
such that and for some
**
where is the Green function (7) and . Then the -dimensional system of fractional finite difference equations (1) has at least one solution.*

*Proof. *Consider the operator defined by (17) and the cone . It is clear that is completely continuous because it is a summation operator on a finite set. Choose such that
for all . Put . Then, and for all . Also, we have
for all . Hence,
for all . Now, choose such that and
for all . Also, choose such that . Now, put . Then, and
for all . Thus, by using (25) we get
for all . Hence,
for all . By using Lemma 3, has at least one fixed point in and so by using Lemma 4, the -dimensional system of fractional finite difference equations (1) has at least one solution.

#### 4. Example

Here, we provide an example to illustrate our last result.

*Example 1. *Consider the 5-dimensional fractional finite difference equation system:
We show that the problem has at least one solution, where
Let , , , , , , and . Thus, the system (29) is a special case of the system (1). It is easy to check that for . Put ,
and for . Then, by a calculation we get , , , , and . Thus, . On the other hand by calculation of some limits, one can get that , , , , , , , , , and . Moreover, we have
Similarly, we obtain
Now, let . Then, and we have
Thus by using Theorem 6, the 5-dimensional system of fractional finite difference equations (29) has at least one solution.

#### 5. Conclusions

In this paper, based on main idea of Goodrich we review the existence of solutions for a -dimensional system of fractional finite difference equations. In fact we are going to extend the work of Goodrich in a sense. We give an example to illustrate our last result.

#### Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

#### Acknowledgments

Research of the second and third authors was supported by Azarbaijan Shahid Madani University. Also, the authors express their gratitude to the referees for their helpful suggestions which improved the final version of this paper.

#### References

- D. Baleanu, K. Diethelm, E. Scalas, and J. J. Trujillo,
*Fractional Calculus Models and Numerical Methods*, World Scientific, 2012. View at Publisher · View at Google Scholar · View at MathSciNet - R. Hilfer,
*Applications of Fractional Calculus in Physics*, World Scientific, 2000. - A. A. Kilbas, H. M. Srivastava, and J. J. Trujillo,
*Theory and Application of Fractional Differential Equations*, Elsevier, Amsterdam, The Netherlands, 2006. - R. L. Magin,
*Fractional Calculus in Bioengineering*, Begell House, 2006. - F. Mainardi,
*Fractional Calculus and Waves in Linear Viscoelasticity: An Introduction to Mathematical Models*, Imperial College Press, 2010. - K. S. Miller and B. Ross, “Fractional difference calculus,” in
*Proceedings of the International Symposium on Univalent Functions, Fractional Calculus and Their Applications*, Nihon University, Tokyo, Japan, 1988. - K. S. Miller and B. Ross, “Fractional difference calculus,” in
*Univalent Functions, Fractional Calculus and Their Applications*, Ellis Horwood Series in Mathematics and Its Applications, pp. 139–152, Horwood, Chichester, UK, 1989. View at Google Scholar - I. Podlubny,
*Fractional Differential Equations*, Academic Press, 1999. View at MathSciNet - G. Samko, A. A. Kilbas, and O. I. Marichev,
*Fractional Integrals and Derivatives: Theory and Applications*, Gordon and Breach, Yverdon, Switzerland, 1993. - F. M. Atıcı and S. Şengül, “Modeling with fractional difference equations,”
*Journal of Mathematical Analysis and Applications*, vol. 369, no. 1, pp. 1–9, 2010. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - G.-C. Wu and D. Baleanu, “Discrete fractional logistic map and its chaos,”
*Nonlinear Dynamics*, vol. 75, no. 1-2, pp. 283–287, 2014. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - F. M. Atici and P. W. Eloe, “Initial value problems in discrete fractional calculus,”
*Proceedings of the American Mathematical Society*, vol. 137, no. 3, pp. 981–989, 2009. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - P. Awasthi,
*Boundary value problems for discrete fractional equations [Ph.D. thesis]*, University of Nebraska-Lincoln, 2013. - G. C. Wu and D. Baleanu, “Discrete chaos of fractional sine and standard maps,”
*Physics Letters A*, vol. 378, pp. 484–487, 2013. View at Google Scholar - F. M. Atici and P. W. Eloe, “A transform method in discrete fractional calculus,”
*International Journal of Difference Equations*, vol. 2, no. 2, pp. 165–176, 2007. View at Google Scholar · View at MathSciNet - F. M. Atıcı and P. W. Eloe, “Discrete fractional calculus with the nabla operator,”
*Electronic Journal of Qualitative Theory of Differential Equations. Special Edition I*, no. 3, pp. 1–12, 2009. View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - B. Ahmad and S. K. Ntouyas, “A boundary value problem of fractional differential equations with anti-periodic type integral boundary conditions,”
*Journal of Computational Analysis and Applications*, vol. 15, no. 8, pp. 1372–1380, 2013. View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - C. S. Goodrich, “Solutions to a discrete right-focal fractional boundary value problem,”
*International Journal of Difference Equations*, vol. 5, no. 2, pp. 195–216, 2010. View at Google Scholar · View at MathSciNet - C. S. Goodrich, “Some new existence results for fractional difference equations,”
*International Journal of Dynamical Systems and Differential Equations*, vol. 3, no. 1-2, pp. 145–162, 2011. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - C. S. Goodrich, “On a fractional boundary value problem with fractional boundary conditions,”
*Applied Mathematics Letters*, vol. 25, no. 8, pp. 1101–1105, 2012. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - M. Holm, “Sum and difference compositions in discrete fractional calculus,”
*Cubo*, vol. 13, no. 3, pp. 153–184, 2011. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - M. Holm,
*The theory of discrete fractional calculus: development and applications [Ph.D. thesis]*, University of Nebraska-Lincoln, 2011. - Sh. Kang, Y. Li, and H. Chen, “Positive solutions to boundary value problems of fractional difference equation with nonlocal conditions,”
*Advances in Differential Equations*, vol. 2014, article 7, 2014. View at Publisher · View at Google Scholar - Y. Pan, Z. Han, S. Sun, and Y. Zhao, “The existence of solutions to a system of discrete fractional boundary value problems,”
*Abstract and Applied Analysis*, vol. 2012, Article ID 707631, 15 pages, 2012. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - S. N. Elaydi,
*An Introduction to Difference Equations*, Springer, 1996. View at MathSciNet - J. J. Mohan and G. V. S. R. Deekshitulu, “Fractional order difference equations,”
*International Journal of Differential Equations*, vol. 2012, Article ID 780619, 11 pages, 2012. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - Sh. Rezapour and R. Hamlbarani, “Some notes on the paper, ‘Cone metric spaces and fixed point theorems of contractive mappings’,”
*Journal of Mathematical Analysis and Applications*, vol. 345, pp. 719–724, 2008. View at Google Scholar - R. P. Agarwal, M. Meehan, and D. O'Regan,
*Fixed Point Theory and Applications*, Cambridge University Press, 2001. View at Publisher · View at Google Scholar · View at MathSciNet - D. R. Dunninger and H. Wang, “Existence and multiplicity of positive solutions for elliptic systems,”
*Nonlinear Analysis: Theory, Methods & Applications A: Theory and Methods*, vol. 29, no. 9, pp. 1051–1060, 1997. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - J. Henderson, S. K. Ntouyas, and I. K. Purnaras, “Positive solutions for systems of nonlinear discrete boundary value problems,”
*Journal of Difference Equations and Applications*, vol. 15, no. 10, pp. 895–912, 2009. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet