Cyclicity of stable matrix free polynomials over non-commutative operator unit balls

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Auteurs principaux: Sampat, Jeet, Tornes, Maximilian
Format: Preprint
Publié: 2026
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author Sampat, Jeet
Tornes, Maximilian
author_facet Sampat, Jeet
Tornes, Maximilian
contents We consider the algebra of square matrices of bounded non-commutative (NC) functions over NC operator unit balls (unit balls corresponding to finite-dimensional operator spaces) and characterize cyclic matrix free polynomials with respect to the canonical weak-* topology. More precisely, we show that a matrix free polynomial generates a weak-* dense left/right ideal if and only if it is stable, i.e., non-singular at every point in the NC operator unit ball. To this end, we establish a version of the Neuwirth--Ginsberg--Newman inequality for stable matrix free polynomials. We combine our techniques with the theory of realizations to establish cyclicity of stable NC rational functions that are uniformly continuous across the boundary, and we recover known results about cyclicity of NC rational functions in the matrix-valued free Hardy space over the NC unit row-ball. Lastly, we introduce the NC parallel sum function: a stable NC rational function that is contractive over the NC bidisk, which cannot be extended uniformly across the boundary, and determine its cyclicity using properties of accretive operators.
format Preprint
id arxiv_https___arxiv_org_abs_2603_22129
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Cyclicity of stable matrix free polynomials over non-commutative operator unit balls
Sampat, Jeet
Tornes, Maximilian
Functional Analysis
Complex Variables
Operator Algebras
Primary: 46L52, Secondary: 15A45, 32A08, 42B30, 47A16
We consider the algebra of square matrices of bounded non-commutative (NC) functions over NC operator unit balls (unit balls corresponding to finite-dimensional operator spaces) and characterize cyclic matrix free polynomials with respect to the canonical weak-* topology. More precisely, we show that a matrix free polynomial generates a weak-* dense left/right ideal if and only if it is stable, i.e., non-singular at every point in the NC operator unit ball. To this end, we establish a version of the Neuwirth--Ginsberg--Newman inequality for stable matrix free polynomials. We combine our techniques with the theory of realizations to establish cyclicity of stable NC rational functions that are uniformly continuous across the boundary, and we recover known results about cyclicity of NC rational functions in the matrix-valued free Hardy space over the NC unit row-ball. Lastly, we introduce the NC parallel sum function: a stable NC rational function that is contractive over the NC bidisk, which cannot be extended uniformly across the boundary, and determine its cyclicity using properties of accretive operators.
title Cyclicity of stable matrix free polynomials over non-commutative operator unit balls
topic Functional Analysis
Complex Variables
Operator Algebras
Primary: 46L52, Secondary: 15A45, 32A08, 42B30, 47A16
url https://arxiv.org/abs/2603.22129