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            5. Functional Analysis, Operator Theory and Operator Algebras, Mathematical Physics
             
            
            $C^*$-algebras  from  $k$ group representations
            Valentin Deaconu
              University of Nevada, Reno, USA
            
    
            Abstract:
            
               We introduce certain $C^*$-algebras and $k$-graphs associated to $k$
               finite dimensional unitary representations $\rho_1,...,\rho_k$ of a compact group $G$.
               We define a higher rank Doplicher-Roberts algebra $\mathcal O_{\rho_1,...,\rho_k}$, constructed from intertwiners of tensor powers of  these representations.
Under certain conditions, we show that this $C^*$-algebra is  isomorphic to a corner in the $C^*$-algebra of  a row finite rank $k$ graph $\Lambda$ with no sources. For $G$ finite and $\rho_i$ faithful of dimension at least $2$, this graph is irreducible, it has vertices $\hat{G}$ and the edges are determined by $k$ commuting matrices obtained from the character table of the group.
We illustrate with some examples when $\mathcal O_{\rho_1,...,\rho_k}$ is simple and purely infinite, and with some $K$-theory computations.