UC Berkeley

Commutative Algebra and Algebraic Geometry Seminar

October 30, 2012

939 Evans Hall

3:45PM: Torsion in tensor powers of modules

Srikanth Iyengar

The starting point of this talk is the observation that if a finitely generated module M over a noetherian (commutative!) domain R is NOT free, then its d-fold tensor-product has torsion for each d > rank_RM. In fact, when R is a regular local ring, torsion shows up already when d >= dim R; this is one of the central results in Auslander's 1961 paper “Modules over unramified regular local rings”. Recently Celikbas, Piepmeyer, R. Wiegand and I extended this result to certain modules over isolated hypersurface singularities; the preprint will be posted on the arXiv soon. My goal is to discuss some ideas that go into its proof. The main new tool is Hochster's theta-function, and is inspired by recent work of Dao.

5:00PM: Linear resolutions of powers of edge ideals of anti-cycles.

Vu Thanh

Let $I$ be the edge ideal of an anticycle of length at least $5$. We will show that all powers $I^k$, for $k \ge 2$ have linear resolution.

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