All Hilbert spaces are the same: consequences for generalized coordinates and momenta

Fuente: arXiv
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Autores principales: van Enk, S. J., Steck, Daniel A.
Formato: Preprint
Publicado: 2025
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author van Enk, S. J.
Steck, Daniel A.
author_facet van Enk, S. J.
Steck, Daniel A.
contents Making use of the simple fact that all separable complex Hilbert spaces of given dimension are isomorphic, we show that there are just six basic ways to define generalized coordinate operators in Quantum Mechanics. In each case a canonically conjugate generalized momentum operator can be defined, but it may not be self-adjoint. Even in those cases we show there is always either a self-adjoint extension of the operator or a Neumark extension of the Hilbert space that produces a self-adjoint momentum operator. In one of the six cases both extensions work, thus leading to seven basic pairs of coordinate and momentum operators. We also show why there are more ways of defining basic coordinate and momentum measurements. A special role is reserved for measurements that simultaneously measure both.
format Preprint
id arxiv_https___arxiv_org_abs_2502_08494
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle All Hilbert spaces are the same: consequences for generalized coordinates and momenta
van Enk, S. J.
Steck, Daniel A.
Quantum Physics
Mathematical Physics
Making use of the simple fact that all separable complex Hilbert spaces of given dimension are isomorphic, we show that there are just six basic ways to define generalized coordinate operators in Quantum Mechanics. In each case a canonically conjugate generalized momentum operator can be defined, but it may not be self-adjoint. Even in those cases we show there is always either a self-adjoint extension of the operator or a Neumark extension of the Hilbert space that produces a self-adjoint momentum operator. In one of the six cases both extensions work, thus leading to seven basic pairs of coordinate and momentum operators. We also show why there are more ways of defining basic coordinate and momentum measurements. A special role is reserved for measurements that simultaneously measure both.
title All Hilbert spaces are the same: consequences for generalized coordinates and momenta
topic Quantum Physics
Mathematical Physics
url https://arxiv.org/abs/2502.08494