English

Gluing derived equivalences together

Representation Theory 2012-11-07 v3 Category Theory

Abstract

The Grothendieck construction of a diagram XX of categories can be seen as a process to construct a single category \Gr(X)\Gr(X) by gluing categories in the diagram together. Here we formulate diagrams of categories as colax functors from a small category II to the 2-category \kCat\kCat of small \k\k-categories for a fixed commutative ring \k\k. In our previous paper we defined derived equivalences of those colax functors. Roughly speaking two colax functors X,X ⁣:I\kCatX, X' \colon I \to \kCat are derived equivalent if there is a derived equivalence from X(i)X(i) to X(i)X'(i) for all objects ii in II satisfying some "II-equivariance" conditions. In this paper we glue the derived equivalences between X(i)X(i) and X(i)X'(i) together to obtain a derived equivalence between Grothendieck constructions \Gr(X)\Gr(X) and \Gr(X)\Gr(X'), which shows that if colax functors are derived equivalent, then so are their Grothendieck constructions. This generalizes and well formulates the fact that if two \k\k-categories with a GG-action for a group GG are "GG-equivariantly" derived equivalent, then their orbit categories are derived equivalent. As an easy application we see by a unified proof that if two k\Bbbk-algebras AA and AA' are derived equivalent, then so are the path categories AQAQ and AQA'Q for any quiver QQ; so are the incidence categories ASAS and ASA'S for any poset SS; and so are the monoid algebras AGAG and AGA'G for any monoid GG. Also we will give examples of gluing of many smaller derived equivalences together to have a larger derived equivalence.

Keywords

Cite

@article{arxiv.1204.0196,
  title  = {Gluing derived equivalences together},
  author = {Hideto Asashiba},
  journal= {arXiv preprint arXiv:1204.0196},
  year   = {2012}
}

Comments

28 pages. 2nd version: many changes with oplax --> colax. 3rd version: minor changes including "The k-flatness assumption was added to apply Keller's theorem on derived equivalences of categories."

R2 v1 2026-06-21T20:43:01.096Z