No Arabic abstract
Riordan matrices are infinite lower triangular matrices determined by a pair of formal power series over the real or complex field. These matrices have been mainly studied as combinatorial objects with an emphasis placed on the algebraic or combinatorial structure. The present paper contributes to the linear algebraic discussion with an analysis of Riordan matrices by means of the interaction of the properties of formal power series with the linear algebra. Specifically, it is shown that if a Riordan matrix $A$ is an $ntimes n$ pseudo-involution then the singular values of $A$ must come in reciprocal pairs in $Sigma$ of a singular value decomposition $A=USigma V^T$. Moreover, we give a complete analysis of the existence and nonexistence of eigenvectors of Riordan matrices. As a result, we obtain a surprising partition of the group of Riordan matrices into three different types of eigenvectors. Finally, given a nonzero vector $v$, we investigate the algebraic structure of Riordan matrices $A$ that stabilize the vector $v$, i.e. $Av=v$.
We identify the dimension of the centralizer of the symmetric group $mathfrak{S}_d$ in the partition algebra $mathcal{A}_d(delta)$ and in the Brauer algebra $mathcal{B}_d(delta)$ with the number of multidigraphs with $d$ arrows and the number of disjoint union of directed cycles with $d$ arrows, respectively. Using Schur-Weyl duality as a fundamental theory, we conclude that each centralizer is related with the $G$-invariant space $P^d(M_n(mathbf{k}))^G$ of degree $d$ homogeneous polynomials on $n times n$ matrices, where $G$ is the orthogonal group and the group of permutation matrices, respectively. Our approach gives a uniform way to show that the dimensions of $P^d(M_n(mathbf{k}))^G$ are stable for sufficiently large $n$.
This paper studies commuting matrices in max algebra and nonnegative linear algebra. Our starting point is the existence of a common eigenvector, which directly leads to max analogues of some classical results for complex matrices. We also investigate Frobenius normal forms of commuting matrices, particularly when the Perron roots of the components are distinct. For the case of max algebra, we show how the intersection of eigencones of commuting matrices can be described, and we consider connections with Boolean algebra which enables us to prove that two commuting irreducible matrices in max algebra have a common eigennode.
Consider the special linear Lie algebra $mathfrak{sl}_n(mathbb {K})$ over an infinite field of characteristic different from $2$. We prove that for any nonzero nilpotent $X$ there exists a nilpotent $Y$ such that the matrices $X$ and $Y$ generate the Lie algebra $mathfrak{sl}_n(mathbb {K})$.
In this paper, we construct self-dual codes from a construction that involves both block circulant matrices and block quadratic residue circulant matrices. We provide conditions when this construction can yield self-dual codes. We construct self-dual codes of various lengths over F2 and F2 + uF2. Using extensions, neighbours and sequences of neighbours, we construct many new self-dual codes. In particular, we construct one new self-dual code of length 66 and 51 new self-dual codes of length 68.
In this paper we characterize those linear bijective maps on the monoid of all $n times n$ square matrices over an anti-negative semifield which preserve and strongly preserve each of Greens equivalence relations $mathcal{L}, mathcal{R}, mathcal{D}, mathcal{J}$ and the corresponding three pre-orderings $leq_mathcal{L}, leq_mathcal{R}, leq_mathcal{J}$. These results apply in particular to the tropical and boolean semirings, and for these two semirings we also obtain corresponding results for the $mathcal{H}$ relation.