1996/10/16 by Tamotsu Teruya, Teruya, Tamotsu · 1 citation
Mathematics · #Algebraic structures and combinatorial models #FOS: Mathematics #Finite Group Theory Research #Functional Analysis (math.FA) #Operator Algebras (math.OA) #Rings, Modules, and Algebras #funct-an #math.OA
paper · pdf · doi:10.48550/arxiv.funct-an/9610002
25 pages, amslatex, to appear in J. Math. Soc. Japan
arxiv created 1996/10/16 · openalex publication_date 1996/10/16 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Let N ⊂ M be an irreducible inclusion of type type II1 factors with finite Jones index. We shall introduce the notion of normality for intermediate subfactors of the inclusion N ⊂ M. If the depth of N ⊂ M is 2, then an intermediate subfactor K for N ⊂ M is normal in N ⊂ M if and only if the depths of N ⊂ K and K ⊂ M are both 2. In particular, if M is the crossed product N \rtimes G of a finite group G, then K = N \rtimes H is normal in N ⊂ M if and only if H is a normal subgroup of G.