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Independence polynomials of circulants with an application to music. (English) Zbl 1228.05178

Summary: The independence polynomial of a graph \(G\) is the generating function \(I(G,x)=\sum _{k\geq 0}i_{k}x^{k}\), where \(i_k\) is the number of independent sets of cardinality \(k\) in \(G\). We show that the problem of evaluating the independence polynomial of a graph at any fixed non-zero number is intractable, even when restricted to circulants. We provide a formula for the independence polynomial of a certain family of circulants, and its complement. As an application, we derive a formula for the number of chords in an \(n\)-tet musical system (one where the ratio of frequencies in a semitone is \(2^{1/n}\)) without ‘close’ pitch classes.

MSC:

05C31 Graph polynomials
05C69 Vertex subsets with special properties (dominating sets, independent sets, cliques, etc.)
05C90 Applications of graph theory
Full Text: DOI

References:

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