Explicit homotopy limits of $mathrm{dg}$-categories and twisted complexes

摘要

In this paper we study the homotopy limits of cosimplicial diagrams of $mathrm{dg}$-categories. We first give an explicit construction of the totalization of such a diagram and then show that the totalization agrees with the homotopy limit in the following two cases: (1) the complexes of sheaves of $mathcal{O}$-modules on the ?ech nerve of an open cover of a ringed space $(X, mathcal{O})$; (2) the complexes of sheaves on the simplicial nerve of a discrete group $G$ acting on a space. The explicit models we obtain in this way are twisted complexes as well as their $D$-module and $G$-equivariant versions. As an application we show that there is a stack of twisted perfect complexes.