English

A 3x3 dilation counterexample

Operator Algebras 2014-02-26 v1 Functional Analysis

Abstract

We define four 3x3 commuting contractions which do not dilate to commuting isometries. However they do satisfy the scalar von Neumann inequality. These matrices are all nilpotent of order 2. We also show that any three 3×33\times3 commuting contractions which are scalar plus nilpotent of order 2 do dilate to commuting isometries.

Cite

@article{arxiv.1203.0062,
  title  = {A 3x3 dilation counterexample},
  author = {Man Duen Choi and Kenneth R. Davidson},
  journal= {arXiv preprint arXiv:1203.0062},
  year   = {2014}
}

Comments

11 pages

R2 v1 2026-06-21T20:27:20.106Z