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Proceedings of the American Mathematical Society

ISSN 1088-6826(online) ISSN 0002-9939(print)



A commutativity theorem for semibounded operators in hilbert space

Author: A. Edward Nussbaum
Journal: Proc. Amer. Math. Soc. 125 (1997), 3541-3545
MSC (1991): Primary 47B25
MathSciNet review: 1402881
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Abstract: Let $A$ and $B$ be semibounded (bounded from below) operators in a Hilbert space $\mathfrak H$ and $\mathfrak D$ a dense linear manifold contained in the domains of $AB$, $BA$, $A^2$, and $B^2$, and such that $ABx=BAx$ for all $x$ in $\mathfrak D$. It is shown that if the restriction of $(A+B)^2$ to $\mathfrak D$ is essentially self-adjoint, then $A$ and $B$ are essentially self-adjoint and $\bar A$ and $\bar B$ commute, i.e. their spectral projections permute.

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A. Edward Nussbaum
Affiliation: Department of Mathematics, Washington University, St. Louis, Missouri 63130

Received by editor(s): April 30, 1996
Dedicated: Dedicated to Allen Devinatz
Communicated by: Palle E. T. Jorgensen
Article copyright: © Copyright 1997 American Mathematical Society