Noncommutative $H^p$ spaces associated with type 1 subdiagonal algebras

TL;DR

This paper develops a Riesz type factorization theorem and a Beurling type invariant subspace theorem for noncommutative $H^p$ spaces associated with type 1 subdiagonal algebras in von Neumann algebras, revealing structural properties and lattice commutativity.

Contribution

It introduces a Riesz factorization theorem and invariant subspace results for noncommutative $H^p$ spaces linked to type 1 subdiagonal algebras, extending classical analysis to the noncommutative setting.

Findings

Existence of factorization $h=h_ph_q$ in noncommutative $H^p$ spaces.

Establishment of a Beurling type invariant subspace theorem.

The relative invariant subspace lattice $Lat_{rak M}rak A$ is shown to be commutative.

Abstract

Let $\mathfrak A$ be a type 1 subdiagonal algebra in a $\sigma$-finite von Neumann algebra $\mathcal M$ with respect to a faithful normal conditional expectation $\Phi$. We consider a Riesz type factorization theorem in noncommutative $H^p$ spaces associated with $\mathfrak A$. It is shown that if $1\leq r,p,q<\infty$ such that $\frac1r=\frac1p+\frac1q$, then for any $h\in H^r$, there exist $h_p\in H^p$ and $h_q\in H^q$ such that $h=h_ph_q$. Beurling type invariant subspace theorem for noncommutative $L^p(1< p<\infty)$ space is obtained. Furthermore, we show that a $\sigma$-weakly closed subalgebra containing $\mathfrak A$ of $\mathcal M$ is also a type 1 subdiagonal algebra. As an application, We prove that the relative invariant subspace lattice $Lat_{\mathcal M}\mathfrak A$ of $\mathfrak A$ in $\mathcal M$ is commutative.