Tuesday, 26 April 2011

homotopy theory - Do h-coequalizers and coproducts give all h-colimits?

It is well known that if a category has all coequalizers and all (small) coproducts then in fact it has all (small) colimits. More important is the proof which shows that every colimit can be built by using coproducts and coequalizers. This implies that if a functor commutes with coproducts and coequalizers, then it must commute with all (small) colimits as well.




Is there homotopical analog of this? If I have a functor which commutes with all small (homotopy) coproducts and all homotopy coequalizers, does it necessarily commute with all homotopy colimits in general?




This question makes sense for general model categories, but I am particularly interested in the usual model structure on spaces.

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