Free function theory through matrix invariants

Abstract

In this article we introduce powerful tools and techniques from invariant theory to free analysis. This enables us to study free maps with involution. These maps are free noncommutative analogs of real analytic functions of several variables. With examples we demonstrate that they do not exhibit strong rigidity properties of their involution-free free counterparts. We present a characterization of polynomial free maps via properties of their finite-dimensional slices. This is used to establish power series expansions for analytic free maps about scalar and non-scalar points; the latter are given by series of generalized polynomials for which we obtain an invariant-theoretic characterization. Finally, we give an inverse and implicit function theorem for free maps with involution.