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### Divisorial linear algebra over normal affine semigroup rings

**Algebra & Discrete Mathematics**

Speaker: | Winfried Bruns, Universitat Osnabrueck Germany |

Location: | 0 Kerr |

Start time: | Fri, Feb 28 2003, 12:10PM |

In joint work with J. Gubeladze we have explored the ``linear algebra'' properties of divisorial ideals over normal semigroup rings. In invariant theory these ideals appear as modules of semi-invariants of the actions of algebraic tori. The properties and invariants to be discussed are, among other things, the Cohen-Macaulayness and the number of generators. In particular we show that there exist, up to isomorphism, only finitely many Cohen-Macaulay (divisorial) ideals.