Virtual fundamental classes, global normal cones and Fulton's canonical classes
Abstract
Description
This paper, first written in 1997, aims at a simplified and more elementary construction of algebraic-geometric virtual fundamental classes as defined by Li/Tian and Behrend/Fantechi. We replace the use of Artin stacks in the latter approach by a yoga of cone bundles of possible independent interest. We also observe a formula for virtual fundamental classes involving only the total Chern class of the index bundle and Fulton's canonical class of the moduli space.
This version differs from the published text in correcting statements on mere dependence of cohomology rather than homotopy. These were based on a flawed splitting statement, as pointed out by Charles Cadman. Moreover, the proof of Proposition 2.11 required more attention. 16 pages
This version differs from the published text in correcting statements on mere dependence of cohomology rather than homotopy. These were based on a flawed splitting statement, as pointed out by Charles Cadman. Moreover, the proof of Proposition 2.11 required more attention. 16 pages