English

The homotopy-invariance of constructible sheaves

Algebraic Topology 2022-09-09 v5

Abstract

The purpose of this paper is to explain why the functor that sends a stratified topological space SS to the \infty-category of constructible (hyper)sheaves on SS with coefficients in a large class of presentable \inftycategories is homotopy-invariant. To do this, we first establish a number of results in the unstratified setting, i.e., the setting of locally constant (hyper)sheaves. For example, if XX is a locally weakly contractible topological space and E\mathcal{E} is a presentable \infty-category, then we give a concrete formula for the constant hypersheaf functor EShhyp(X;E)\mathcal{E}\to \mathrm{Sh}^{\mathrm{hyp}}(X;\mathcal{E}). This formula lets us show that the constant hypersheaf functor is a right adjoint, and is fully faithful if XX is also weakly contractible. It also lets us prove a general monodromy equivalence and categorical K\"unneth formula for locally constant hypersheaves.

Keywords

Cite

@article{arxiv.2010.06473,
  title  = {The homotopy-invariance of constructible sheaves},
  author = {Peter J. Haine and Mauro Porta and Jean-Baptiste Teyssier},
  journal= {arXiv preprint arXiv:2010.06473},
  year   = {2022}
}

Comments

28 pages. Comments very welcome! v5. Clarified a few things and added some remarks. A slightly shorter version of this paper will appear in Homology, Homotopy and Applications. v4. Completely revised. Two new authors. Much stronger results. v3. Fixed the definition of a "constructible hypersheaf" and clarified a few points. v2. Fixed some typos