The von Neumann inequality for matrices in the unit Euclidean ball
arXiv:2310.12908 · doi:10.1007/s11856-025-2740-3
Abstract
It is shown that the constant in von Neumann's inequality for d-tuples of commutative and row contractive matrices, as proved by Hartz, Richter, and Shalit in [2], is independent of the size of the d-tuple. A numerical estimation of the constant is provided.
The article was published in the Israel Journal of Mathematics