The Local Operator Moment Problem on $\mathbb{R}$

TL;DR

This paper investigates the operator moment problem on the real line, establishing conditions for solutions, exploring subnormal operators, and discussing operator moment sequences with compact support.

Contribution

It provides necessary and sufficient conditions for solving the operator moment problem on , including criteria for recursive sequences and applications to subnormal operator weighted shifts.

Findings

Criteria are automatically valid on compact subsets of .

A Stampfli-type propagation theorem for subnormal operator weighted shifts is established.

Conditions for the operator recursive moment problem are provided.

Abstract

We study the connections between operator moment sequences ${\mathcal T}=\displaystyle(T_n)_{n\in\mathbb{Z}_+}$ of self-adjoint operators on a complex Hilbert space $\mathcal{H}$ and the local moment sequences $\langle{\mathcal T}x,x\rangle = (\langle T_nx,x\rangle)_{n\in\mathbb{Z}_+}$ for arbitrary $x\in \mathcal{H}$. We provide necessary and sufficient conditions for solving the operator moment problem on $\mathbb{R}$, and we show that these criteria are automatically valid on compact subsets of $\mathbb{R}$. Applications of the compact case are used to study subnormal operator weighted shifts. A Stampfli-type propagation theorem for subnormal operator weighted shifts is also established. In addition, we discuss the validity of Tchakaloff's Theorem for operator moment sequences with compact support. In the case of a recursively generated sequence of self-adjoint operators, necessary and sufficient conditions for an affirmative answer to the operator recursive moment problem are provided, and the support of the associated representing operator-valued measure is described.