Spans of quantum-inequality projections

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1. Verfasser: Chirvasitu, Alexandru
Format: Preprint
Veröffentlicht: 2025
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author Chirvasitu, Alexandru
author_facet Chirvasitu, Alexandru
contents A hereditarily atomic von Neumann algebra $A$ is a $W^*$ product of matrix algebras, regarded as the underlying function algebra of a quantum set. Projections in $A\overline{\otimes}A^{\circ}$ are interpreted as quantum binary relations on $A$, with the supremum of all $p\otimes (1-p)$ representing quantum inequality. We prove that the symmetrized weak$^*$-closed linear span of all such quantum-inequality projections is precisely the symmetric summand of the joint kernel of multiplication and opposite multiplication, a result valid without the symmetrization qualification for plain matrix algebras. The proof exploits the symmetries of the spaces involved under the compact unitary group of $A$, and related results include a classification of those von Neumann algebras (hereditarily atomic or not) for which the unitary group operates jointly continuously with respect to the weak$^*$ topology.
format Preprint
id arxiv_https___arxiv_org_abs_2504_01746
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Spans of quantum-inequality projections
Chirvasitu, Alexandru
Operator Algebras
Functional Analysis
Quantum Algebra
Rings and Algebras
Representation Theory
17B10, 22E47, 18M05, 22D10, 46L05, 46L10, 16D25, 03G12
A hereditarily atomic von Neumann algebra $A$ is a $W^*$ product of matrix algebras, regarded as the underlying function algebra of a quantum set. Projections in $A\overline{\otimes}A^{\circ}$ are interpreted as quantum binary relations on $A$, with the supremum of all $p\otimes (1-p)$ representing quantum inequality. We prove that the symmetrized weak$^*$-closed linear span of all such quantum-inequality projections is precisely the symmetric summand of the joint kernel of multiplication and opposite multiplication, a result valid without the symmetrization qualification for plain matrix algebras. The proof exploits the symmetries of the spaces involved under the compact unitary group of $A$, and related results include a classification of those von Neumann algebras (hereditarily atomic or not) for which the unitary group operates jointly continuously with respect to the weak$^*$ topology.
title Spans of quantum-inequality projections
topic Operator Algebras
Functional Analysis
Quantum Algebra
Rings and Algebras
Representation Theory
17B10, 22E47, 18M05, 22D10, 46L05, 46L10, 16D25, 03G12
url https://arxiv.org/abs/2504.01746