Jordan chains of h-cyclic matrices, II

Perturbations of Jordan matrices

We consider perturbations of a large Jordan matrix, either random and small in norm or of small rank. In both cases we show that most of the eigenvalues of the perturbed matrix are very close to a circle with centre at the origin. In the case of random perturbations we obtain an estimate of the number of eigenvalues that are well inside the circle in a certain asymptotic regime. In the case of ...

Infinite-dimensional versions of the primary, cyclic and Jordan decompositions

The famous primary and cyclic decomposition theorems along with the tightly related rational and Jordan canonical forms are extended to linear spaces of infinite dimensions with counterexamples showing the scope of extensions.

Reachability matrices and cyclic matrices

Formality of Cyclic Chains

We prove a conjecture raised by Tsygan [12], namely the existence of an L∞-quasiisomorphism of L∞-modules between the cyclic chain complex of smooth functions on a manifold and the differential forms on that manifold. Concretely, we prove that the obvious u-linear extension of Shoikhet’s morphism of Hochschild chains solves Tsygan’s conjecture.

Lipschitz stability of canonical Jordan bases of H-selfadjoint matrices under structure-preserving perturbations

In this paper we study Jordan-structure-preserving perturbations of matrices selfadjoint in the indefinite inner product. The main result of the paper is Lipschitz stability of the corresponding similitude matrices. The result can be reformulated as Lipschitz stability, under small perturbations, of canonical Jordan bases (i.e., eigenvectors and generalized eigenvectors enjoying a certain flipp...