Lattice of intermediate subalgebras

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Hauptverfasser: Bakshi, Keshab Chandra, Gupta, Ved Prakash
Format: Preprint
Veröffentlicht: 2020
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author Bakshi, Keshab Chandra
Gupta, Ved Prakash
author_facet Bakshi, Keshab Chandra
Gupta, Ved Prakash
contents Analogous to subfactor theory, employing Watatani's notions of index and $C^*$-basic construction of certain inclusions of $C^*$-algebras, (a) we develop a Fourier theory (consisting of Fourier transforms, rotation maps and shift operators) on the relative commutants of any inclusion of simple unital $C^*$-algebras with finite Watatani index, and (b) we introduce the notions of interior and exterior angles between intermediate $C^*$-subalgebras of any inclusion of unital $C^*$-algebras admitting a finite index conditional expectation. Then, on the lines of [2], we apply these concepts to obtain a bound for the cardinality of the lattice of intermediate $C^*$-subalgebras of any irreducible inclusion as in (a), and improve Longo's bound for the cardinality of intermediate subfactors of an inclusion of type $III$ factors with finite index. Moreover, we also show that for a fairly large class of inclusions of finite von Neumann algebras, the lattice of intermediate von Neumann subalgebras is always finite.
format Preprint
id arxiv_https___arxiv_org_abs_2005_01049
institution arXiv
publishDate 2020
record_format arxiv
spellingShingle Lattice of intermediate subalgebras
Bakshi, Keshab Chandra
Gupta, Ved Prakash
Operator Algebras
Functional Analysis
47L40, 46L05, 46L37
Analogous to subfactor theory, employing Watatani's notions of index and $C^*$-basic construction of certain inclusions of $C^*$-algebras, (a) we develop a Fourier theory (consisting of Fourier transforms, rotation maps and shift operators) on the relative commutants of any inclusion of simple unital $C^*$-algebras with finite Watatani index, and (b) we introduce the notions of interior and exterior angles between intermediate $C^*$-subalgebras of any inclusion of unital $C^*$-algebras admitting a finite index conditional expectation. Then, on the lines of [2], we apply these concepts to obtain a bound for the cardinality of the lattice of intermediate $C^*$-subalgebras of any irreducible inclusion as in (a), and improve Longo's bound for the cardinality of intermediate subfactors of an inclusion of type $III$ factors with finite index. Moreover, we also show that for a fairly large class of inclusions of finite von Neumann algebras, the lattice of intermediate von Neumann subalgebras is always finite.
title Lattice of intermediate subalgebras
topic Operator Algebras
Functional Analysis
47L40, 46L05, 46L37
url https://arxiv.org/abs/2005.01049