MOS

Abstract

Recent work of Behrend, Bryan and Szendroi gives a nice handle on the degree zero motivic Donaldson-Thomas invariants of threefolds, in which the calculation of the invariants of a single point in smooth three dimensional space plays the key role. I will explain how fat points fit naturally into the theory of 3-Calabi-Yau categories, and also what kind of contributions they make. In contrast with the smooth case, the story here throws up complicated motives and monodromy actions, and it is possible to see directly here the role played by the concept of orientation data.