Frobenius subalgebra lattices in tensor categories

Fuente: arXiv
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Main Authors: Ghosh, Mainak, Palcoux, Sebastien
Format: Preprint
Published: 2025
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_version_ 1866909866579197952
author Ghosh, Mainak
Palcoux, Sebastien
author_facet Ghosh, Mainak
Palcoux, Sebastien
contents This paper studies Frobenius subalgebra posets in abelian monoidal categories and shows that, under general conditions--satisfied in all semisimple tensor categories over the complex field--they collapse to lattices through a rigidity invariance perspective. Based on this, we extend Watatani's finiteness theorem for intermediate subfactors by proving that, under a weak positivity assumption--met by all semisimple tensor categories over the complex field--and a compatibility condition--fulfilled by all pivotal ones--the lattices arising from connected Frobenius algebras are finite. We also derive a non-semisimple version via semisimplification. Our approach relies on the concept of a formal angle, and the extension of key results--such as the planar algebraic exchange relation and Landau's theorems--to linear monoidal categories. Major applications of our findings include a stronger version of the Ino-Watatani result: we show that the finiteness of intermediate C*-algebras holds in a finite-index unital irreducible inclusion of C*-algebras without requiring the simple assumption. Moreover, for a finite-dimensional semisimple Hopf algebra H, we prove that H* is a Frobenius algebra object in Rep(H) and has a finite number of rigid invariant Frobenius subalgebras. Finally, we explore a range of applications, including abstract spin chains, vertex operator algebras and speculations on quantum arithmetic involving the generalization of Ore's theorem, Euler's totient and sigma functions, and RH.
format Preprint
id arxiv_https___arxiv_org_abs_2502_19876
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Frobenius subalgebra lattices in tensor categories
Ghosh, Mainak
Palcoux, Sebastien
Quantum Algebra
Combinatorics
Category Theory
Operator Algebras
Rings and Algebras
18M20, 46L37 (Primary) 05E16, 16T05, 17B69, 18M05, 46L05 (Secondary)
This paper studies Frobenius subalgebra posets in abelian monoidal categories and shows that, under general conditions--satisfied in all semisimple tensor categories over the complex field--they collapse to lattices through a rigidity invariance perspective. Based on this, we extend Watatani's finiteness theorem for intermediate subfactors by proving that, under a weak positivity assumption--met by all semisimple tensor categories over the complex field--and a compatibility condition--fulfilled by all pivotal ones--the lattices arising from connected Frobenius algebras are finite. We also derive a non-semisimple version via semisimplification. Our approach relies on the concept of a formal angle, and the extension of key results--such as the planar algebraic exchange relation and Landau's theorems--to linear monoidal categories. Major applications of our findings include a stronger version of the Ino-Watatani result: we show that the finiteness of intermediate C*-algebras holds in a finite-index unital irreducible inclusion of C*-algebras without requiring the simple assumption. Moreover, for a finite-dimensional semisimple Hopf algebra H, we prove that H* is a Frobenius algebra object in Rep(H) and has a finite number of rigid invariant Frobenius subalgebras. Finally, we explore a range of applications, including abstract spin chains, vertex operator algebras and speculations on quantum arithmetic involving the generalization of Ore's theorem, Euler's totient and sigma functions, and RH.
title Frobenius subalgebra lattices in tensor categories
topic Quantum Algebra
Combinatorics
Category Theory
Operator Algebras
Rings and Algebras
18M20, 46L37 (Primary) 05E16, 16T05, 17B69, 18M05, 46L05 (Secondary)
url https://arxiv.org/abs/2502.19876