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Free Product C*-algebras Associated with Graphs, Free Differentials, and Laws of Loops
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- Journal:
- Canadian Journal of Mathematics / Volume 69 / Issue 3 / 01 June 2017
- Published online by Cambridge University Press:
- 20 November 2018, pp. 548-578
- Print publication:
- 01 June 2017
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- Article
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We study a canonical
${{\text{C}}^{*}}$-algebra, 
$\text{S}\left( \Gamma ,\mu \right)$, that arises from a weighted graph 
$\left( \Gamma ,\mu \right)$, specific cases of which were previously studied in the context of planar algebras. We discuss necessary and sufficient conditions of the weighting that ensure simplicity and uniqueness of trace of $\text{S}\left( \Gamma ,\mu \right)$, and study the structure of its positive cone. We then study the 
$*$-algebra, 
$\mathcal{A}$, generated by the generators of $\text{S}\left( \Gamma ,\mu \right)$, and use a free differential calculus and techniques of Charlesworth and Shlyakhtenko as well as Mai, Speicher, and Weber to show that certain “loop” elements have no atoms in their spectral measure. After modifying techniques of Shlyakhtenko and Skoufranis to show that self adjoint elements
$x\,\in \,{{M}_{n}}\left( \mathcal{A} \right)$ have algebraic Cauchy transform, we explore some applications to eigenvalues of polynomials in Wishart matrices and to diagrammatic elements in von Neumann algebras initially considered by Guionnet, Jones, and Shlyakhtenko.
