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Conic divisorial ideals and non-commutative crepant resolutions of edge rings of complete multipartite graphs. (English) Zbl 1483.13027

Authors’ abstract: The first goal of the present paper is to study the class groups of the edge rings of complete multipartite graphs, denoted by \(\Bbbk[K_{r_1,\dots,r_n}]\), where \(1\leq r_1\leq \ldots\leq r_n\). More concretely, we prove that the class group of \(\Bbbk[K_{r_1,\dots,r_n}]\) is isomorphic to \(\mathbb{Z}^n\) if \(n=3\) with \(r_1\geq 2\) or \(n\geq 4\), while it turns out that the excluded cases can be deduced into Hibi rings. The second goal is to investigate the special class of divisorial ideals of \(\Bbbk[K_{r_1,\dots,r_n}]\), called conic divisorial ideals. We describe conic divisorial ideals for certain \(K_{r_1,\dots,r_n}\) including all cases where \(\Bbbk[K_{r_1,\dots,r_n}]\) is Gorenstein. Finally, we give a non-commutative crepant resolution (NCCR) of \(\Bbbk[K_{r_1,\dots,r_n}]\) in the case where it is Gorenstein.

MSC:

13C14 Cohen-Macaulay modules
13F65 Commutative rings defined by binomial ideals, toric rings, etc.
14M25 Toric varieties, Newton polyhedra, Okounkov bodies
05C25 Graphs and abstract algebra (groups, rings, fields, etc.)
52B20 Lattice polytopes in convex geometry (including relations with commutative algebra and algebraic geometry)

Software:

Macaulay2

References:

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