The noncommutative Löwner theorem for matrix monotone functions over operator systems

2017/06/26 by J. E. Pascoe, Pascoe, J. E.
Mathematics · #Advanced Operator Algebra Research #Holomorphic and Operator Theory #Mathematical Inequalities and Applications

paper · pdf · doi:10.48550/arxiv.1706.08236

Abstract

Given a function f: (a,b) → ℝ, Löwner's theorem states f is monotone when extended to self-adjoint matrices via the functional calculus, if and only if f extends to a self-map of the complex upper half plane. In recent years, several generalizations of Löwner's theorem have been proven in several variables. We use the relaxed Agler, McCarthy and Young theorem on locally matrix monotone functions in several commuting variables to generalize results in the noncommutative case. Specifically, we show that a real free function defined over an operator system must analytically continue to a noncommutative upper half plane as map into another noncommutative upper half plane.

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