English

The eigenvector variety of a matrix pencil

Numerical Analysis 2017-05-02 v2 Algebraic Geometry Representation Theory

Abstract

Let kk be a field and n,a,bn,a,b natural numbers. A matrix pencil PP is given by nn matrices of the same size with coefficients in kk, say by (b×a)(b\times a)-matrices, or, equivalently, by nn linear transformations αikakb\alpha_i\:k^a \to k^b with 1=1,,n1=1,\dots,n. We say that PP is reduced provided the intersection of the kernels of the linear transformations αi\alpha_i is zero. If PP is a reduced matrix pencil, a vector vkav\in k^a will be called an eigenvector of PP provided the subspace α1(v),,αn(v)\langle \alpha_1(v),\dots,\alpha_n(v) \rangle of kbk^b generated by the elements α1(v),,αn(v)\alpha_1(v),\dots,\alpha_n(v) is 11-dimensional. Eigenvectors are called equivalent provided they are scalar multiples of each other. The set ϵ(P)\epsilon(P) of equivalence classes of eigenvectors of PP is a Zariski closed subset of the projective space P(ka)\Bbb P(k^a), thus a projective variety. We call it the eigenvector variety of PP. The aim of this note is to show that any projective variety arises as an eigenvector variety of some reduced matrix pencil.

Keywords

Cite

@article{arxiv.1703.04097,
  title  = {The eigenvector variety of a matrix pencil},
  author = {Claus Michael Ringel},
  journal= {arXiv preprint arXiv:1703.04097},
  year   = {2017}
}

Comments

The presentation has been polished. We have added the remark that any projective variety can be realized by using matrix pencils of square matrices

R2 v1 2026-06-22T18:43:25.029Z