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We present two new canonical forms for real congruence of a real square matrix $A$. The first one is a direct sum of canonical matrices of four different types and is obtained from the canonical form under $^*$congruence of complex matrices…

Spectral Theory · Mathematics 2025-10-09 Fernando De Terán , Froilán M. Dopico

Canonical matrices are given for (a) bilinear forms over an algebraically closed or real closed field; (b) sesquilinear forms over an algebraically closed field and over real quaternions with any nonidentity involution; and (c) sesquilinear…

Representation Theory · Mathematics 2007-12-17 Roger A. Horn , Vladimir V. Sergeichuk

We use methods of the general theory of congruence and *congruence for complex matrices--regularization and cosquares-to determine a unitary congruence canonical form (respectively, a unitary *congruence canonical form) for complex matrices…

Representation Theory · Mathematics 2012-12-14 Roger A. Horn , Vladimir V. Sergeichuk

We develop a canonical form for congruence of max plus symmetric matrices. We use the same canonical form to get results in the generalized eigenvector problem. We have also utilized the canonical form to find all symmetric matrices that…

Rings and Algebras · Mathematics 2024-10-17 Himadri Mukherjee , Askar Ali M

We give canonical matrices of a pair (A,B) consisting of a nondegenerate form B and a linear operator A satisfying B(Ax,Ay)=B(x,y) on a vector space over F in the following cases: (i) F is an algebraically closed field of characteristic…

Representation Theory · Mathematics 2007-12-17 Vladimir V. Sergeichuk

Canonical matrices of (a) bilinear and sesquilinear forms, (b) pairs of forms, in which every form is symmetric or skew-symmetric, and (c) pairs of Hermitian forms are given over finite fields of characteristic not 2 and over finite…

Representation Theory · Mathematics 2010-11-16 Vladimir V. Sergeichuk

Tridiagonal canonical forms of square matrices under congruence or *congruence, pairs of symmetric or skew-symmetric matrices under congruence, and pairs of Hermitian matrices under *congruence are given over an algebraically closed field…

Representation Theory · Mathematics 2008-01-14 Vyacheslav Futorny , Roger A. Horn , Vladimir V. Sergeichuk

Let $\mathbb F$ be a field of characteristic not $2$, and let $(A,B)$ be a pair of $n\times n$ matrices over $\mathbb F$, in which $A$ is symmetric and $B$ is skew-symmetric. A canonical form of $(A,B)$ with respect to congruence…

Representation Theory · Mathematics 2017-10-02 Victor A. Bovdi , Roger A. Horn , Mohamed A. Salim , Vladimir V. Sergeichuk

First, we prove that the set of $n\times n$ complex matrices is the closure of a certain open subset whose elements have a very specific canonical form under congruence, which is uniquely determined up to the values of some parameters, but…

Spectral Theory · Mathematics 2025-12-16 Fernando De Terán , Froilán M. Dopico

We derive the canonical forms for a pair of $n\times n$ complex matrices $(E,Q)$ under transformations $(E,Q) \rightarrow (UEV,U^{-T}QV)$, and $(E,Q) \rightarrow (UEV,U^{-*}QV)$, where $U$ and $V$ are nonsingular complex matrices. We, in…

Representation Theory · Mathematics 2025-10-30 Sweta Das , Andrii Dmytryshyn , Volker Mehrmann

Results on matrix canonical forms are used to give a complete description of the higher rank numerical range of matrices arising from the study of quantum error correction. It is shown that the set can be obtained as the intersection of…

Functional Analysis · Mathematics 2011-02-10 Chi-Kwong Li , Nung-Sing Sze

Motivated by a problem in local differential geometry of Cauchy--Riemann (CR) structures of hypersurface type, we find a canonical form for pairs consisting of a nondegenerate Hermitian form and a self-adjoint antilinear operator, or,…

Complex Variables · Mathematics 2020-06-24 David Sykes , Igor Zelenko

We devise a method that reduces the problem of classifying systems of forms and linear mappings to the problem of classifying systems of linear mappings. Canonical matrices of (i) bilinear or sesquilinear forms, (ii) pairs of symmetric,…

Representation Theory · Mathematics 2008-01-08 Vladimir V. Sergeichuk

Structured canonical forms under unitary and suitable structure-preserving similarity transformations for normal and (skew-)Hamiltonian as well as normal and per(skew)-Hermitian matrices are proposed. Moreover, an algorithm for computing…

Numerical Analysis · Mathematics 2024-03-19 Erna Begovic , Heike Fassbender , Philip Saltenberger

Matrix congruence can be used to mimic linear maps between homogeneous quadratic polynomials in $n$ variables. We introduce a generalization, called standard-form congruence, which mimics affine maps between non-homogeneous quadratic…

Rings and Algebras · Mathematics 2018-09-19 Jason Gaddis

Let $(A,B)$ be a pair of skew-symmetric matrices over a field of characteristic not 2. Its regularization decomposition is a direct sum \[ (\underline{\underline A},\underline{\underline B})\oplus (A_1,B_1)\oplus\dots\oplus(A_t,B_t) \] that…

Representation Theory · Mathematics 2017-12-27 V. A. Bovdi , T. G. Gerasimova , M. A. Salim , V. V. Sergeichuk

In this paper many classes of sets of matrices with entries in F (F=R, F=C, F=H) are introduced. Each class with the corresponding topology determines a real analytical, complex or symplectic manifold for F=R, F=C or F=H respectively. Any…

Differential Geometry · Mathematics 2007-05-23 Kostadin Trencevski , Samet Kera

This article studies canonical forms derived from the finest simultaneous block diagonalization of a set of symmetric matrices via congruence. Our technique relies on Harrison's center theory, which is extended from a single higher degree…

Rings and Algebras · Mathematics 2025-12-22 Lishan Fang , Hua-Lin Huang , Jiayan Huang

V.I. Arnold [Russian Math. Surveys 26(2) (1971) 29-43] constructed a miniversal deformation of a square complex matrix under similarity; that is, a simple normal form to which not only a given square matrix A but all matrices B close to it…

Representation Theory · Mathematics 2014-01-21 A. Dmytryshyn , V. Futorny , V. V. Sergeichuk

Docovic and Szechtman, [Proc. Amer. Math. Soc. 133 (2005) 2853-2863] considered a vector space V endowed with a bilinear form. They proved that all isometries of V over a field F of characteristic not 2 have determinant 1 if and only if V…

Representation Theory · Mathematics 2010-04-22 Tatyana G. Gerasimova , Roger A. Horn , Vladimir V. Sergeichuk
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