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Mathlib.CategoryTheory.Localization.DerivabilityStructure.OfLocalizedEquivalences

Derivability structures deduced from localized equivalences #

Assume that we have a diagram of localizer morphisms, in the sense that we have an isomorphism T.functor ⋙ R.functor ≅ L.functor ⋙ B.functor.

      T
 W₁  ---> W₂
 |        |
L|        |R
 v        v
 W₁' ---> W₂'
      B

In this file, we obtain the lemma LocalizerMorphism.isRightDerivabilityStructure_of_isLocalizedEquivalence which shows that if both L and R are localized equivalences (with R.functor essentially surjective), then B is a right derivability structure when T is a right derivability structure, the 2-square above is Guitart exact (and W₂' respects isomorphisms). In addition, if we require that L.functor is also essentially surjective, that R.functor is full and that W₂ is induced by W₂', then B is a right derivability structure iff T is.

The dual results for left derivability structures are also obtained.

This will be particularly useful when L.functor and R.functor are functors from a category to a quotient category (e.g. functors from categories of homological complexes to homotopy categories).