Analytic Model of Doubly Commuting Contractions

Abstract: An n-tuple (n \geq 2), T = (T_1, \ldots, T_n), of commuting bounded linear operators on a Hilbert space \mathcal{H} is doubly commuting if T_i T_j^* = T_j^* T_i for all $1 \leq i < j \leq n$. If in addition, each T_i \in C_{\cdot 0}, then we say that T is a doubly commuting pure tuple. In this paper we prove that a doubly commuting pure tuple $T$ can be dilated to a tuple of shift operators on some suitable vector-valued Hardy space H^2_{\mathcal{D}_{T^*}}(\mathbb{D}^n). As a consequence of the dilation theorem, we prove that there exists a closed subspace \mathcal{S}T of the form [\mathcal{H}{T} := \sum_{i=1}^n \Phi_{T_i} H^2_{\mathcal{E}_{T_i}}(\mathbb{D}^n),] where {\mathcal{E}{T_i}}{i=1}^n are Hilbert spaces, \Phi_{T_i} \in H^\infty_{\mathcal{B}(\mathcal{E}_{T_i}, \mathcal{D}{T^*})}(\mathbb{D}^n) such that each \Phi{T_i} (1 \leq i \leq n) is either a one variable inner function in z_i, or the zero function. Moreover, \mathcal{H} \cong \mathcal{S}T^\perp and [(T_1, \ldots, T_n) \cong P{\mathcal{S}T^\perp} (M{z_1}, \ldots, M_{z_n})|_{\mathcal{S}_T^\perp}.]