The generic canonical form for $^\star$congruence of matrices
Abstract
First, we prove that the set of 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 which has a slightly different expression depending on whether is even or odd. As a consequence, the canonical form under congruence of the elements of this subset can be considered the generic canonical form under congruence of complex matrices. Second, we prove that the set of complex matrices is the union of the closures of certain open subsets and that, for each of these subsets, its elements have a very specific canonical form under congruence, which is uniquely determined up to the values of some parameters. As a consequence, the canonical forms under congruence of the elements of each of these subsets can be considered the generic canonical forms under congruence of complex matrices. So, there is only one generic canonical form under congruence whereas the number of generic canonical forms under congruence is instead, which reveals a strong dichotomy between the relations of congruence and congruence with respect to generic structures. In other words, we determine in this paper the generic matrix representations of bilinear and sesquilinear forms in .
Cite
@article{arxiv.2512.12407,
title = {The generic canonical form for $^\star$congruence of matrices},
author = {Fernando De Terán and Froilán M. Dopico},
journal= {arXiv preprint arXiv:2512.12407},
year = {2025}
}