Subnormal and completely hyperexpansive completion problem of weighted shifts on directed trees

Abstract: For a given directed tree and weights associated with vertices from a subtree the completion problem is to determine if these weights may be completed in a way to obtain a bounded weighted shift on the whole tree, which possibly satisfies also some more restrictive conditions. In this paper we consider subnormal and completely hyper-expansive completion problem for weighted shifts on directed trees with one branching point. We develop new results on backward extensions of truncated moment sequences and, exploiting these results, we obtain a characterization of existence of such a completion