English

Categorical quotients for actions of groupoids on varieties

Algebraic Geometry 2025-01-24 v1 Representation Theory

Abstract

For certain actions of the Weyl groupoid W\mathfrak{W} from [Sergeev and Veselov, Grothendieck rings of basic classical Lie superalgebras, Ann Math, 2011] on an affine variety XX, geometric properties of the map π:XY=Spec  O(X)W\pi: X \longrightarrow Y= {\operatorname{Spec }\;} \mathcal{O}(X)^\mathfrak{W} were studied in [Musson, On the geometry of some algebras related to the Weyl groupoid, Contemp. Math. 2024], In this paper we show that if the base field k{\mathtt k} is uncountable, the map π\pi is a geometric quotient which is universal in the category of k{\mathtt k}-schemes. To do this we adapt a result from [{Mumford}, {Fogarty}, {Kirwan}, {1994}], showing that a geometric quotient is universal in the category of k{\mathtt k}-schemes, to quotients by groupoids and more generally by equivalence relations. In our approach a key role is played by the closed points and Jacobson schemes.

Keywords

Cite

@article{arxiv.2501.13510,
  title  = {Categorical quotients for actions of groupoids on varieties},
  author = {Ian M. Musson},
  journal= {arXiv preprint arXiv:2501.13510},
  year   = {2025}
}