Corners of Graph Algebras
نویسنده
چکیده
It is known that given a directed graph E and a subset X of vertices, the sum Σ v∈X P v of vertex projections in the C *-algebra of E converges strictly in the multiplier algebra to a projection P X. Here we give a construction which, in certain cases, produces a directed graph F such that C * (F) is isomorphic to the corner P X C * (E)P X. Corners of this type arise naturally as the fixed point algebras of discrete coactions on graph algebras related to labellings. We prove this fact, and show that our construction is applicable to such a case whenever the labelling satisfies an analogue of Kirchhoff's voltage law.
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