English

Extensions of $\infty$-group sheaves

Algebraic Geometry 2016-12-30 v1

Abstract

Let X\mathscr X be an \infty-topos, for example the \infty-category of simplicial sheaves on a Grothendieck site. Then \infty-group sheaves are group objects in X\mathscr X. Let AGrpXA\in\mathrm{Grp}\mathscr X be such a group object. Then as X\mathscr X is an \infty-topos, there exists a universal BA\mathbf BA-fiber bundle BA//AutAqBAutA\mathbf BA//\mathbf{Aut} A\xrightarrow q\mathbf B\mathbf{Aut} A. We make qq pointed, and show that as a pointed map, via the looping-delooping equivalence, it is a universal extension of group objects by AA. In particular, semidirect products of group objects by AA are classified by BA//AutA\mathbf BA//\mathbf{Aut} A.

Keywords

Cite

@article{arxiv.1612.09070,
  title  = {Extensions of $\infty$-group sheaves},
  author = {Pal Zsamboki},
  journal= {arXiv preprint arXiv:1612.09070},
  year   = {2016}
}

Comments

10 pages

R2 v1 2026-06-22T17:36:33.222Z