English

The Taylor joint spectrum and restriction to hyperinvariant subspaces

Functional Analysis 2019-11-12 v1 Spectral Theory

Abstract

It is well known that for a single bounded operator A0A_0 on a Hilbert H\mathfrak{H}, if MH\mathfrak{M}\subset \mathfrak{H} is hyperinvariant for A0A_0, then the spectrum of A0MA_0|_{\mathfrak{M}} is contained in the spectrum of A0A_0. In this note, we modify an example of Taylor to prove the following. There exist a quadruple A=(A1,A2,A3,A4)A=(A_1,A_2,A_3,A_4) of commuting bounded Hilbert space operators and a hyperinvariant subspace X1\mathfrak{X}_1 for AA such that the Taylor joint spectrum of AA restricted to X1\mathfrak{X}_1 is a not a subset of the Taylor joint spectrum of AA.

Keywords

Cite

@article{arxiv.1911.03530,
  title  = {The Taylor joint spectrum and restriction to hyperinvariant subspaces},
  author = {Edward J. Timko},
  journal= {arXiv preprint arXiv:1911.03530},
  year   = {2019}
}

Comments

3 pages

R2 v1 2026-06-23T12:09:53.406Z