A note on Cartan isometries

TL;DR

This paper presents a lifting theorem for $S_{\Omega}$-isometries related to subnormal operator tuples in convex domains, generalizing known results and providing new examples and characterizations for classical Cartan domains.

Contribution

It introduces a general lifting theorem for $S_{\Omega}$-isometries, unifies existing results, and offers new intrinsic characterizations for these isometries in classical Cartan domains.

Findings

Unified lifting theorem for $S_{\Omega}$-isometries

New examples of liftings in Cartesian products of Cartan domains

Intrinsic characterizations of $S_{\Omega}$-isometries in classical Cartan domains

Abstract

We record a lifting theorem for the intertwiner of two $S_{\Omega}$-isometries which are those subnormal operator tuples whose minimal normal extensions have their Taylor spectra contained in the Shilov boundary of a certain function algebra associated with $\Omega$, $\Omega$ being a bounded convex domain in $\C^n$ containing the origin. The theorem captures several known lifting results in the literature and yields interesting new examples of liftings as a consequence of its being applicabile to Cartesian products $\Omega$ of classical Cartan domains in $\C^n$. Further, we derive intrinsic characterizations of $S_{\Omega}$-isometries where $\Omega$ is a classical Cartan domain of any of the types I, II, III and IV, and we also provide a neat description of an $S_{\Omega}$-isometry in case $\Omega$ is a finite Cartesian product of such Cartan domains.