Rotation algebras and Exel trace formula

Jiajie Hua, Huaxin Lin

We found that if $u$ and $v$ are any two unitaries in a unital $C^{\ast }$-algebra with $\Vert uv-vu\Vert <2$ such that $uv{u}^{\ast }{v}^{\ast }$ commutes with $u$ and $v,$ then the \SCA\, $A_{u,v}$ generated…