# A NONCOMMUTATIVE BEURLING THEOREM WITH RESPECT TO UNITARILY INVARIANT NORMS

### Abstract

• In 1967, Arveson invented a non-commutative generalization of classical $H^{\infty},$ known as finite maximal subdiagonal subalgebras, for a finite von Neumann algebra $\mathcal M$ with a faithful normal tracial state $\tau$. In 2008, Blecher and Labuschagne proved a version of Beurling's theorem on $H^\infty$-right invariant subspaces in a non-commutative $L^{p}(\mathcal M,\tau)$ space for $1\le p\le \infty$. In the present paper, we define and study a class of norms ${\mathcal{N}}_{c}(\mathcal M, \tau)$ on $\mathcal{M},$ called normalized, unitarily invariant, $\Vert \cdot \Vert_{1}$-dominating, continuous norms, which properly contains the class $\{ \Vert \cdot \Vert_{p}:1\leq p< \infty \}.$ For $\alpha \in \mathcal{N}_{c}(\mathcal M, \tau),$ we define a non-commutative $L^{\alpha }({\mathcal{M}},\tau)$ space and a non-commutative $H^{\alpha}$ space. Then we obtain a version of the Blecher-Labuschagne-Beurling invariant subspace theorem on $H^\infty$-right invariant subspaces in a non-commutative $L^{\alpha }({\mathcal{M}},\tau)$ space. Key ingredients in the proof of our main result include a characterization theorem of $H^\alpha$ and a density theorem for $L^\alpha(\mathcal M,\tau)$.

• Chen, Yanni
• Shen, Junhao

• 2016

### Keywords

• Beurling theorem
• Normalized
• continuous norm
• dual space
• maximal subdiagonal algebra
• noncommutative Hardy space
• parallel to . parallel to(1)-dominating
• unitarily invariant

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