Holmstrom Total derived functor

Let F:CDF: C \to D be a left Quillen functor. Define its total (left) derived functor LF:HoCHoDLF: Ho \ C \to Ho \ D as the composite of

HoQ:HoCHoC c Ho \ Q : Ho \ C \to Ho \ C_c

and

HoF:HoC cHoD Ho \ F : Ho \ C_c \to Ho \ D

Here QQ is the cofibrant replacement functor.

Given a natural transformation τ\tau of left Quillen functors, define the total derived natural transformation LτL \tau to be HoτHoQHo \ \tau \circ Ho \ Q.

Similarly, for a right Quillen functor we define the total (right) derived functor to be

RU=HoUHoR RU = Ho \ U \circ Ho \ R

Consider the 2-category of model cats, left (resp. right) Quillen functors, and natural transformations. The triple: Homotopy category, total derived functor, and total derived natural transformation, define a pseudo-2-functor from this 2-category to the 2-category of categories. SImilar statement with Quillen adjunctions instead of Quillen functor.

Remark: One can define total derived functors in more general settings, I think. For example, Quillen describes the total left derived functor as a Kan extension.

Goerss-Jardine p 122: Quillen’s total derived functor thm, explains when adjoint functors between model cats induces adjoint functors on the homotopy cats. The total left derived functor here is defined for functors from a simplicial model cat to any cat, sending WEs between cofibrant objects to isomorphisms. A version of the theorem is: For an adjoint pair (F, G) between simplicial model cats, the conclusion is true of FF preserves WEs between cofibrant objects and GG WEs between fibrant objects. There are also some corollaries and variations on this theme.

In Goerss and Schemmerhornopology/0609537), page 17, there is a brief description of the spectral sequence total left derived functor of tensor product.

nLab page on Total derived functor

Created on June 9, 2014 at 21:16:13 by Andreas Holmström