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Jean-Michel Vallin

Publications and source records attributed to Jean-Michel Vallin.

8 recordsLinked to original sources
arXiv2020

Yetter-Drinfel'd algebras and coideals of Weak Hopf $C^*$-Algebras

We characterize braided commutative Yetter-Drinfeld $C^*$-algebras over weak Hopf $C^*$-algebras in categorical terms. Using this, we then study quotient type coideal subalgebras of a given weak Hopf $C^*$-algebra $\mathcal G$ and coideal subalgebras invariant with respect to the adjoint action of $\mathcal G$. Finally, as an example, we explicitly describe quotient type coideal subalgebras of the weak Hopf $C^*$-algebras associated with Tambara-Yamagami categories.

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arXiv2019

Classifying (Weak) Coideal Subalgebras of Weak Hopf C*-Algebras

We develop a general approach to the problem of classification of weak coideal C*-subalgebras of weak Hopf C*-algebras. As an example, we consider weak Hopf C*-algebras and their weak coideal C*-subalgebras associated with Tambara Yamagami categories.

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arXiv2006

Actions and coactions of finite quantum groupoids on von Neumann algebras, extensions of the match pair procedure

In this work we investigate the notion of action or coaction of a finite quantum groupoid in von Neumann algebras context. In particular we prove a double crossed product theorem and prove the existence of an universal von Neumann algebra on which any finite groupoids acts outerly. In previous works, N. Andruskiewitsch and S.Natale define for any match pair of groupoids two $C^*$-quantum groupoids in duality, we give here an interpretation of them in terms of crossed products of groupoids using a multiplicative partial isometry which gives a complete description of these structures. In a next work we shall give a third description of these structures dealing with inclusions of depth two inclusions of von Neumann algebras associated with outer actions of match pairs of groupoids, and a study, in the same spirit, of an other extension of the match pair procedure.

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arXiv2003

Deformation of finite dimensional C*-quantum groupoids

In this work we prove, in full details, that any finite dimensional $C^*$-quantum groupoid can be deformed in order that the square of the antipode is the identity on the base. We also prove that for any $C^*$-quantum groupoid with non abelian base, there is uncountably many $C^*$-quantum groupoids with the same underlying algebra structure but which are not isomorphic to it. In fact, the $C^*$-quantum groupoids are closed in an analog of the procedure presented by D.Nikshych ([N] 3.7) in a more general situation.

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