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Automatic closure of invariant linear manifolds for operator algebras. (English) Zbl 1029.47051

Summary: Kadison’s transitivity theorem implies that, for irreducible representations of \(C^*\)-algebras, every invariant linear manifold is closed. It is known that CSL algebras have this property if and only if the lattice is hyperatomic (every projection is generated by a finite number of atoms). We show that several other conditions are equivalent, including the condition that every invariant linear manifold is singly generated.
We show that two families of norm closed operator algebras have this property. First, let \(\mathcal L\) be a CSL and suppose \(\mathcal A\) is a norm closed algebra which is weakly dense in \(\text{Alg}\mathcal L\) and is a bimodule over the (not necessarily closed) algebra generated by the atoms of \(\mathcal L\). If \(\mathcal L\) is hyperatomic and the compression of \(\mathcal A\) to each atom of \(\mathcal L\) is a \(C^*\)-algebra, then every linear manifold invariant under \(\mathcal A\) is closed. Secondly, if \(\mathcal A\) is the image of a strongly maximal triangular AF algebra under a multiplicity free nest representation, where the nest has order type \(-\mathbb{N}\), then every linear manifold invariant under \(\mathcal A\) is closed and is singly generated.

MSC:

47L55 Representations of (nonselfadjoint) operator algebras
47L35 Nest algebras, CSL algebras
47L40 Limit algebras, subalgebras of \(C^*\)-algebras
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