Abstract and Applied Analysis

Volume 2015 (2015), Article ID 951340, 9 pages

http://dx.doi.org/10.1155/2015/951340

## Skew Circulant Type Matrices Involving the Sum of Fibonacci and Lucas Numbers

School of Science, Linyi University, Shuangling Road, Linyi, Shandong 276000, China

Received 27 June 2014; Revised 8 August 2014; Accepted 11 August 2014

Academic Editor: Yongli Song

Copyright © 2015 Zhaolin Jiang and Yunlan Wei. 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

Skew circulant and circulant matrices have been an ideal research area and hot issue for solving various differential equations. In this paper, the skew circulant type matrices with the sum of Fibonacci and Lucas numbers are discussed. The invertibility of the skew circulant type matrices is considered. The determinant and the inverse matrices are presented. Furthermore, the maximum column sum matrix norm, the spectral norm, the Euclidean (or Frobenius) norm, the maximum row sum matrix norm, and bounds for the spread of these matrices are given, respectively.

#### 1. Introduction

As is well-known, skew circulant and circulant matrices play a crucial role for solving various differential equations. Authors in [1] presented the skew circulant matrices as preconditioners for linear multistep formulae (LMF-)based ordinary differential equations (ODEs) codes. Claeyssen et al. [2] discussed factor block circulant and periodic solutions of undamped matrix differential equations. Using circulant matrix, Karasözen and Şimşek [3] considered periodic boundary conditions such that no additional boundary terms will appear after semidiscretization. Meyer and Rjasanow [4] have presented an effective direct solution method for certain boundary element equations in 3D. Guo et al. concerned on generic Dn-Hopf bifurcation to a delayed Hopfield-Cohen-Grossberg model of neural networks (5.17) in [5], where denoted an interconnection matrix. In particular, they assumed that is a symmetric circulant matrix. In [6], Jin et al. proposed the GMRES method with the Strang-type block-circulant preconditioner for solving singular perturbation delay differential equations. In [7], two new normal-form realizations are presented which utilize circulant and skew circulant matrices as their state transition matrices. The well known second-order coupled form is a special case of the skew circulant form. Compared with cyclic convolution algorithm, the skew cyclic convolution algorithm [8] is able to perform filtering procedure in approximately half of computational cost for real signals. In [9], a new fast algorithm for optimal design of block digital filters (BDFs) was proposed based on skew circulant matrix. Spectral decompositions of skew circulant and skew left circulant matrices were discussed in [10]. Li et al. [11] gave the style spectral decomposition of skew circulant matrix firstly and then dealt with the optimal backward perturbation analysis for the linear system with skew circulant coefficient matrix.

Some scholars have given various algorithms for the determinants and inverses of nonsingular circulant matrices [12, 13]. Unfortunately, the computational complexity of these algorithms is very amazing with the order of matrix increasing. However, some authors gave the explicit determinants and inverse of circulant and skew circulant involving some famous numbers. For example, Shen et al. considered circulant matrices with Fibonacci and Lucas numbers and presented their explicit determinants and inverses by constructing the transformation matrices in [14]. Gao et al. [15] gave explicit determinants and inverses of skew circulant and skew left circulant matrices with Fibonacci and Lucas numbers. In [16], Jiang et al. discussed the nonsingularity of the skew circulant type matrices and presented explicit determinants and inverse matrices of these special matrices. Furthermore, four kinds of norms and bounds for the spread of these matrices are given separately. In [17], Jiang and Hong give exact determinants of some special circulant matrices involving four kinds of famous numbers. Authors [18] discussed the nonsingularity of the circulant type matrix and presented the explicit determinant and inverse matrices.

There are several papers on the norms of some special matrices. Solak [19] established the lower and upper bounds for the spectral norms of circulant matrices with classical Fibonacci and Lucas numbers entries. İpek [20] investigated an improved estimation for spectral norms of these matrices.

Beginning with Mirsky [21] several authors [22–24] have obtained bounds for the spread of a matrix.

Additionally, skew circulant type matrices include skew circulant and skew left circulant matrices. The norm and spread of skew circulant type matrices have not been studied. It is hoped that this paper will help in changing this. More work continuing the present paper is forthcoming.

The sum of Fibonacci and Lucas sequence is defined by the following recurrence relations: for . The first few values of the sequence are given by the following table:The is given by the formulawhere and are the roots of the characteristic equation .

In this paper, we consider skew circulant type matrices, including the skew circulant and skew left circulant matrices.

We define a sum of Fibonacci and Lucas skew circulant matrix which is an complex matrix with following form:where each row is a cyclic shift of the row above the right.

Besides, a sum of Fibonacci and Lucas skew left circulant matrix is given bywhere each row is a cyclic shift of the row above the left.

Lemma 1. *Let be the sum of Fibonacci and lucas numbers; then,*

*Proof. *According to we haveand henceThis completes the proof.

*Lemma 2 (see [10]). Let be a skew left circulant matrix and let be odd; then,where are the eigenvalues of .*

*2. Determinant and Inverse of Skew Circulant Matrix with the Sum of Fibonacci and Lucas Numbers*

*In this section, let be a skew circulant matrix. First of all, a determinant explicit formula for the matrix is given. After that, we prove that is an invertible matrix for any positive interger , and then we find the inverse of the matrix . In the following, let *

*Theorem 3. Let be a skew circulant matrix; thenwhere is the th sum of Fibonacci and Lucas numbers.*

*Proof. *Obviously, satisfies the equation. In the case , let be two matrices; then, we havewhereSo it holds thatWhile taking , we have This completes the proof.

*Theorem 4. Let be a skew circulant matrix; then is an invertible matrix for any positive interger .*

*Proof. *Taking in Theorem 3, we have . Hence is invertible. In the case , since , where , we have where , . If there exists such that , we have for , and hence it follows that is a real number. Since it yields that , so we have for . Since is not the root of the equation . We obtain for any , while It follows from Lemma 1 in [25] that the conclusion holds.

*Lemma 5. Let the matrix be of the formThen the inverse of the matrix is equal to*

*Proof. *Let . Obviously, for . In the case , we obtain . For , we obtain Hence, we get ; here is identity matrix. Similarly, we can verify . Thus, the proof is completed.

*Theorem 6. Let be a skew circulant matrix; thenwhere*

*Proof. *Let where Then we haveso , and here is a diagonal matrix, and is the direct sum of and . If we denote , then we obtain . Since the last row elements of the matrix are (), the last row elements of the matrix are (), whereHence it follows from Lemma 5 that by letting then its last row elements are which are given by the following equations: Hence, we obtain where This completes the proof.

*3. Norm and Spread of Skew Circulant Matrix with the Sum of Fibonacci and Lucas Numbers*

*3. Norm and Spread of Skew Circulant Matrix with the Sum of Fibonacci and Lucas Numbers**Theorem 7. Let be a skew circulant matrix. The three kinds norms of are given by*

*Proof. *By Definition 4 in [26], (6), and (7), we haveThus

*Theorem 8. Let be an odd-order alternative skew circulant matrix and let be odd. Then*

*Proof. *By Lemma 1 in [25], we haveTherefore Since is odd, is an eigenvalue of , which is To sum up, we haveSince all skew circulant matrices are normal, by Lemma 7 in [26], (6), and (43), we havewhich completes the proof.

*Theorem 9. Let be a skew circulant matrix; then the bounds for the spread of are*

*Proof. *The trace of is denoted by . By Definition 5 in [26] and (36), we haveSince by (6) and (8), By Lemma 6 in [26], we have

*4. Determinant and Inverse of Skew Left Circulant Matrix with the Sum of Fibonacci and Lucas Numbers*

*4. Determinant and Inverse of Skew Left Circulant Matrix with the Sum of Fibonacci and Lucas Numbers**In this section, let be a skew left circulant matrix. By using the obtained conclusions in Section 2, we give a determinant explicit formula for the matrix . And then, we prove that is an invertible matrix for any positive interger . The inverse of the matrix is also presented.*

*According to Lemmas 4 and 5 in [15] and Theorems 3, 4, and 6, we can obtain the following theorems.*

*Theorem 10. Let be a skew left circulant matrix; then where is the th sum of Fibonacci and Lucas number.*

*Theorem 11. Let be a skew left circulant matrix for any positive interger ; then is an invertible matrix.*

*Theorem 12. Let be a skew left circulant matrix; thenwhere *

*5. Norm and Spread of Skew Left Circulant Matrix with the Sum of Fibonacci and Lucas Numbers*

*5. Norm and Spread of Skew Left Circulant Matrix with the Sum of Fibonacci and Lucas Numbers**Theorem 13. Let be a skew left circulant matrix. Then three kinds norms of are given by*

*Proof. *Using the similar method in Theorem 7, the conclusion is obtained.

*Theorem 14. Let be an odd-order alternative skew left circulant matrix; then*

*Proof. *According to Lemma 2,for , andSoBy (56) and (57), we haveSince all skew left circulant matrices are symmetrical, by Lemma 7 in [26], (6), and (58), we obtain

*Theorem 15. Let be a skew left circulant matrix; then the bounds for the spread of arewhere .*

*Proof. *Since is a symmetric matrix, by Lemma 6 in [26], we get .

The trace of is, if is odd, then , by (6), we haveLet ; then by Definition 5 in [26], (53), and (61), we obtainIf is even, thenhenceSo the result follows.

*6. Conclusion*

*6. Conclusion*

*We discuss the invertibility of the skew circulant type matrices with the sum of Fibonacci and Lucas numbers and present the determinant and the inverse matrices by constructing the transformation matrices. The four kinds of norms and bounds for the spread of these matrices are given, respectively.*

*Conflict of Interests*

*Conflict of Interests*

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

*Acknowledgments*

*Acknowledgments*

*The research is supported by the Development Project of Science & Technology of Shandong Province (Grant no. 2012GGX10115) and the AMEP of Linyi University, China.*

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