English

Toeplitz condition numbers as an $H^{\infty}$ interpolation problem

Functional Analysis 2011-03-28 v1

Abstract

The condition numbers CN(T)==T.T1CN(T)==||T|| .||T^{-1}|| of Toeplitz and analytic n×nn\times n matrices TT are studied. It is shown that the supremum of CN(T)CN(T) over all such matrices with T1||T|| \leq1 and the given minimum of eigenvalues r=mini=1..nλi>0r=min_{i=1..n}|\lambda_{i}|>0 behaves as the corresponding supremum over all n×nn\times n matrices (i.e., as 1rn\frac{1}{r{}^{n}} (Kronecker)), and this equivalence is uniform in nn and rr. The proof is based on a use of the Sarason-Sz.Nagy-Foias commutant lifting theorem.

Keywords

Cite

@article{arxiv.1103.5016,
  title  = {Toeplitz condition numbers as an $H^{\infty}$ interpolation problem},
  author = {Rachid Zarouf},
  journal= {arXiv preprint arXiv:1103.5016},
  year   = {2011}
}
R2 v1 2026-06-21T17:44:38.273Z