On Some Decompositions of Matrices over Algebraically Closed and Finite Fields

We study when every square matrix over an algebraically closed field or over a finite field is decomposable into a sum of a potent matrix and a nilpotent matrix of order 2. This can be related to our recent paper, published in Linear & Multilinear Algebra (2022). We also completely address the question when each square matrix over an infinite field can be decomposed into a periodic matrix and a nilpotent matrix of order 2

Weighted Fractional-Order Transform Based on Periodic Matrix

Tao et al. proposed the definition of the linear summation of fractional-order matrices based on the theory of Yeh and Pei. This definition was further extended and applied to image encryption. In this paper, we propose a reformulation of the definitions of Yeh et al. and Tao et al. and analyze them theoretically. The results show that many weighted terms are invalid. Therefore, we use the proposed reformulation to prove that the effective weighted terms depend on the period of the matrix. This also shows that the image encryption methods based on the weighted fractional-order transform will lead to the security risk of key invalidation. Finally, our hypothesis is verified by the unified theoretical framework of multiple-parameter discrete fractional-order transforms.

Periodic matrix difference equations and companion matrices in blocks: some applications

This study is devoted to some periodic matrix difference equations, through their associated product of companion matrices in blocks. Linear recursive sequences in the algebra of square matrices in blocks and the generalized Cayley–Hamilton theorem are considered for working out some results about the powers of matrices in blocks. Two algorithms for computing the finite product of periodic companion matrices in blocks are built. Illustrative examples and applications are considered to demonstrate the effectiveness of our approach.

Three types of biconjugate residual method for general periodic matrix equations over generalized bisymmetric periodic matrices

As is well known, periodic matrix equations have wide applications in many areas of control and system theory. This paper is devoted to a study of the numerical solutions of a general type of periodic matrix equations. We present three types of biconjugate residual (BCR) method to find the generalized bisymmetric periodic solutions [Formula: see text] of general periodic matrix equations [Formula: see text] The main theorems of this paper show that the presented methods can compute the generalized bisymmetric periodic solutions in a finite number of steps in the absence of round-off errors. We give two numerical examples to illustrate and interpret the theoretical results.