Operator realizations of non-commutative analytic functions

A realization is a triple, $(A,b,c)$ , consisting of a $d-$ tuple, $A= (A_1, \cdots , A_d )$ , $d\in \mathbb {N}$ , of bounded linear operators on a separable, complex Hilbert space, $\mathcal {H}$ , and vectors $b,c \in \mathcal {H}$ . Any such realization define...

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Bibliographic Details
Main Authors: Méric L. Augat, Robert T. W. Martin, Eli Shamovich
Format: Article
Language:English
Published: Cambridge University Press 2025-01-01
Series:Forum of Mathematics, Sigma
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Online Access:https://www.cambridge.org/core/product/identifier/S2050509425100388/type/journal_article
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Summary:A realization is a triple, $(A,b,c)$ , consisting of a $d-$ tuple, $A= (A_1, \cdots , A_d )$ , $d\in \mathbb {N}$ , of bounded linear operators on a separable, complex Hilbert space, $\mathcal {H}$ , and vectors $b,c \in \mathcal {H}$ . Any such realization defines an analytic non-commutative (NC) function in an open neighbourhood of the origin, $0:= (0, \cdots , 0)$ , of the NC universe of $d-$ tuples of square matrices of any fixed size. For example, a univariate realization, i.e., where A is a single bounded linear operator, defines a holomorphic function of a single complex variable, z, in an open neighbourhood of the origin via the realization formula $b^{*} (I-zA)^{-1} c$ .
ISSN:2050-5094