Partial factorization and reflexivity of operator algebras

Abstract

Let $\mathcal{H}$ be a separable infinite dimensional Hilbert space and $\mathcal{B}(\mathcal{H})$ the algebra of all bounded linear operators on $\mathcal{H}$. A subalgebra $\mathfrak{A}$ in $\mathcal{B}(\mathcal{H})$ has the left (resp.\ right) partial factorization property if for any invertible operator $S\in \mathcal{B}(\mathcal{H})$, there exists an isometry (resp.\ a co-isometry) $U\in \mathcal{B}(\mathcal{H})$ such that $U^{\ast }S,S^{-1}U\in \mathfrak{A}$. We show that if $\mathfrak{A}$ is weak operator topology closed with the left (resp.\ right) partial factorization property, then $\mathfrak{A}$ is the nest algebra associated with its invariant subspace lattice. In particular, if $\mathfrak{A}$ is transitive, then $\mathfrak{A}=\mathcal{B}(\mathcal{H})$. This gives a positive answer to Question 6.3 raised by B.V.R. Bhat and M. Kumar in \emph{Publ. Res. Inst. Math. Sci.} \textbf{60}(2024), 507--537.

9 pages