Characteristic functions for multicontractions and automorphisms of the unit ball
arXiv:math/0509094
Abstract
A \emph{multicontraction} on a Hilbert space $\HH$ is an -tuple of operators acting on $\HH$, such that $\sum_{i=1}^n T_i T_i^*\le \1_\HH$. We obtain some results related to the characteristic function of a commuting multicontraction, most notably discussing its behaviour with respect to the action of the analytic automorphisms of the unit ball.