Comparison of congruences and strict equivalences for real, complex, and quaternionic matrix pencils with symmetries.
Complementary triangular forms
The notion of simultaneous reduction of pairs of matrices and linear operators to triangular forms is introduced and a survey of known material on the subject is given. Further, some open problems are pointed out throughout the text. The paper is meant to be accessible to the non-specialist and does not contain any new results or proofs.
Completely simple semigroups of matrices.
Computing codimensions and generic canonical forms for generalized matrix products.
Consimilarity and quaternion matrix equations AX −^X B = C, X − A^X B = C
L. Huang [Consimilarity of quaternion matrices and complex matrices, Linear Algebra Appl. 331 (2001) 21–30] gave a canonical form of a quaternion matrix with respect to consimilarity transformations A ↦ ˜S−1AS in which S is a nonsingular quaternion matrix and h = a + bi + cj + dk ↦ ˜h := a − bi + cj − dk (a, b, c, d ∈ ℝ). We give an analogous canonical form of a quaternion matrix with respect to consimilarity transformations A ↦^S−1AS in which h ↦ ^h is an arbitrary involutive automorphism of the...
Constructing a Canonical form of a Matrix in Several Problems about Combinatorial Designs
Partially supported by the Bulgarian Science Fund contract with TU Varna, No 487.The author developed computer programs needed for the classification of designs with certain automorphisms by the local approach method. All these programs use canonicity test or/and construction of canonical form of an integer matrix. Their efficiency substantially influences the speed of the whole computation. The present paper deals with the implemented canonicity algorithm. It is based on ideas used by McKay, Meringer,...
Controllability of series connections.
Correction to "Generalized approximation numbers" (Port. Math., 43(1) (1985-1986), 157-166)
Criteria of unitary equivalence of Hermitian operators with a degenerate spectrum.
Deformations of bimodule problems
We prove that deformations of tame Krull-Schmidt bimodule problems with trivial differential are again tame. Here we understand deformations via the structure constants of the projective realizations which may be considered as elements of a suitable variety. We also present some applications to the representation theory of vector space categories which are a special case of the above bimodule problems.
Diagonal and von Neumann regular matrices over a Dedekind domain.
Diagonal reductions of matrices over exchange ideals
In this paper, we introduce related comparability for exchange ideals. Let be an exchange ideal of a ring . If satisfies related comparability, then for any regular matrix , there exist left invertible and right invertible such that for idempotents .
Diagonal similarity and equivalence for matrices over groups with 0
Diagonal similarity of matrices
Dissident maps on the seven-dimensional Euclidean space
Our article contributes to the classification of dissident maps on ℝ ⁷, which in turn contributes to the classification of 8-dimensional real division algebras. We study two large classes of dissident maps on ℝ ⁷. The first class is formed by all composed dissident maps, obtained from a vector product on ℝ ⁷ by composition with a definite endomorphism. The second class is formed by all doubled dissident maps, obtained as the purely imaginary parts of the structures of those 8-dimensional...
Edge matrices for the fundamental cone.
Eigenvalue multiplicities of products of companion matrices.
Eigenvalues of partially prescribed matrices.
Eight-dimensional real quadratic division algebras.
Elementary linear algebra for advanced spectral problems
We describe a simple linear algebra idea which has been used in different branches of mathematics such as bifurcation theory, partial differential equations and numerical analysis. Under the name of the Schur complement method it is one of the standard tools of applied linear algebra. In PDE and spectral analysis it is sometimes called the Grushin problem method, and here we concentrate on its uses in the study of infinite dimensional problems, coming from partial differential operators of mathematical...