الجبر

The University of Michigan Algebra Seminar

Winter 2007, Tuesday 3:10-4:00, 3096 East Hall

(organized by Harm Derksen and Toby Stafford)

February 5, Paczki Day, Jerzy Weyman, Northeastern University
The Boij-Soderberg conjectures on Betti numbers of graded modules
Abstract: I will report on the contents of two recent papers: "The Existence of Pure Free Resolutions" by Eisenbud, Floystad, and myself (arXiv:0709.1529) and "Betti Numbers of Graded Modules and Cohomology of Vector Bundles" by Eisenbud and Schreyer (arXiv:0712.1843). These two papers give the proof of Boij-Soderberg conjectures on Betti diagrams of graded Cohen-Macaulay modules over polynomial rings over a field of characteristic zero. These conjectures imply the multiplicity conjectures of Herzog-Huneke and Srinivasan.
March 25, Travis Schedler, University of Chicago
Differential operators in noncommutative geometry
Abstract: Motivated by Van den Bergh's recent `double Poisson' algebras, we introduce a new formalism of differential operators for a general associative algebra A. It replaces Grothendieck's notion for commutative algebras in such a way that derivations of a commutative algebra are replaced by Der(A, A ⊗ A), the A-bimodule of `double derivations' of A. The algebra D(A) of differential operators is filtered, and its associated graded is commutative in some `twisted' sense. Parallel to the commutative case, there is an induced double Poisson structure on gr(A), which identifies gr(A) with Van den Bergh's `double Schouten-Nijenhuis algebra', TA Der(A, A ⊗ A), which is a noncommutative version of polyvector fields on a variety.

A crucial step of our construction is replacing A with a certain `Fock space' F(A), which carries the structure of a wheeled PROP.

We then consider the case where A is the path algebra of a quiver, which may be viewed as a `noncommutative' version of affine space. The original motivation for the above constructions was to construct a `wheeled BV' structure on the double Schouten-Nijenhuis algebra of A, which justifies calling A a `wheeled Calabi-Yau' algebra. In this case, D(A) generalizes the quiver version of the Moyal star product on Rn, and is also a quiver version of Turaev's skein algebra of links on surfaces.

Last modified: 3/15/08, maintained by Harm Derksen.