## Quantum automorphisms of twisted group algebras and free hypergeometric laws

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- by Teodor Banica, Julien Bichon and Stephen Curran
- Proc. Amer. Math. Soc.
**139**(2011), 3961-3971 - DOI: https://doi.org/10.1090/S0002-9939-2011-10877-3
- Published electronically: March 15, 2011
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## Abstract:

We prove that we have an isomorphism of type $A_{aut}(\mathbb C_\sigma [G])\simeq A_{aut}(\mathbb C[G])^\sigma$, for any finite group $G$, and any $2$-cocycle $\sigma$ on $G$. In the particular case $G=\mathbb Z_n^2$, this leads to a Haar measure-preserving identification between the subalgebra of $A_o(n)$ generated by the variables $u_{ij}^2$ and the subalgebra of $A_s(n^2)$ generated by the variables $X_{ij}=\sum _{a,b=1}^np_{ia,jb}$. Since $u_{ij}$ is “free hyperspherical” and $X_{ij}$ is “free hypergeometric”, we obtain in this way a new free probability formula, which at $n=\infty$ corresponds to the well-known relation between the semicircle law and the free Poisson law.## References

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## Bibliographic Information

**Teodor Banica**- Affiliation: Department of Mathematics, Cergy-Pontoise University, 95000 Cergy-Pontoise, France
- Email: teodor.banica@u-cergy.fr
**Julien Bichon**- Affiliation: Department of Mathematics, Clermont-Ferrand University, Campus des Cezeaux, 63177 Aubiere Cedex, France
- MR Author ID: 633469
- Email: bichon@math.univ-bpclermont.fr
**Stephen Curran**- Affiliation: Department of Mathematics, University of California, Berkeley, California 94720
- Address at time of publication: Department of Mathematics, University of California, Los Angeles, California 90095
- Email: curransr@math.berkeley.edu, curransr@math.ucla.edu
- Received by editor(s): February 16, 2010
- Received by editor(s) in revised form: September 13, 2010
- Published electronically: March 15, 2011
- Communicated by: Marius Junge
- © Copyright 2011
American Mathematical Society

The copyright for this article reverts to public domain 28 years after publication. - Journal: Proc. Amer. Math. Soc.
**139**(2011), 3961-3971 - MSC (2010): Primary 46L65; Secondary 16W30, 46L54
- DOI: https://doi.org/10.1090/S0002-9939-2011-10877-3
- MathSciNet review: 2823042