# On C.N.C. Commuting Contractive Tuples

Bhattacharyya, T and Eschmeier, J and Sarkar, J (2005) On C.N.C. Commuting Contractive Tuples. In: Proceedings of Indian Academy of Sciences: Mathematical Sciences, 116 (4). pp. 299-316. (In Press)

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The characteristic function has been an important tool for studying completely non unitary contractions on Hilbert spaces. In this note, we consider completely non-coisometric contractive tuples of commuting operators on a Hilbert space $\mathcal{H}$. We show that the characteristic function, which is now an operator valued analytic function on the open Euclidean unit ball in $\mathbb{C}^n$, is a complete unitary invariant for such a tuple. We prove that the characteristic function satisfies a natural transformation law under biholomorphic mappings of the unit ball. We also characterize all operator-valued analytic functions which arise as characteristic functions of pure commuting contractive tuples.