Virtual signed Euler characteristics
Abstract
Roughly speaking, to any space with perfect obstruction theory we associate a space with symmetric perfect obstruction theory. It is a cone over given by the dual of the obstruction sheaf of , and contains as its zero section. It is locally the critical locus of a function. More precisely, in the language of derived algebraic geometry, to any quasi-smooth space we associate its -shifted cotangent bundle . By localising from to its -fixed locus this gives five notions of virtual signed Euler characteristic of : (1) The Ciocan-Fontanine-Kapranov/Fantechi-G\"ottsche signed virtual Euler characteristic of defined using its own obstruction theory, (2) Graber-Pandharipande's virtual Atiyah-Bott localisation of the virtual cycle of to , (3) Behrend's Kai-weighted Euler characteristic localisation of the virtual cycle of to , (4) Kiem-Li's cosection localisation of the virtual cycle of to , (5) times by the topological Euler characteristic of . Our main result is that (1)=(2) and (3)=(4)=(5). The first two are deformation invariant while the last three are not.
Cite
@article{arxiv.1408.2541,
title = {Virtual signed Euler characteristics},
author = {Yunfeng Jiang and Richard P Thomas},
journal= {arXiv preprint arXiv:1408.2541},
year = {2024}
}
Comments
Referees' corrections and improvements