Four-dimensional operator systems without the lifting property
Abstract
The purpose of this note is to provide a family of explicit examples of -dimensional operator systems contained in the Calkin algebra on a separable infinite-dimensional Hilbert space for which the identity map has no unital completely positive (ucp) lift to with respect to the canonical quotient map . More specifically, to each unital -algebra generated by unitaries and unital -homomorphism with no ucp lift, we construct a four-dimensional operator subsystem of without the lifting property. As a result, for each we exhibit a four-dimensional operator system in without the lifting property. We also obtain explicit examples where the generalized Smith-Ward problem for liftings of joint matrix ranges for three self-adjoint operators has a negative answer.
Cite
@article{arxiv.2508.00113,
title = {Four-dimensional operator systems without the lifting property},
author = {Samuel J. Harris},
journal= {arXiv preprint arXiv:2508.00113},
year = {2025}
}
Comments
9 pages