Comparison morphism for the composition of right derived functors #
F₁₂ F₂₃
C₁ ⥤ C₂ = C₃
L₁| L₂| L₃|
v v v
D₁ ⥤ D₂ ⥤ D₃
RF₁₂ RF₂₃
In the situation above, when we have natural transformations
α₁₂ : F₁₂ ⋙ L₂ ⟶ L₁ ⋙ RF₁₂, α₂₃ : F₂₃ ⋙ L₃ ⟶ L₂ ⋙ RF₂₃,
an isomorphism e : F₁₂ ⋙ F₂₃ ≅ F₁₃ where F₁₃ : C₁ ⥤ C₃,
and a natural transformation α₁₃ : F₁₃ ⋙ L₃ ⟶ L₁ ⋙ RF₁₃
which makes RF₁₃ the derived functor of of F₁₃ ⋙ L₃
(with respect to W₁ : MorphismProperty C₁),
we define a natural transformation RF₁₃ ⟶ RF₁₂ ⋙ RF₂₃
(see Functor.natTransOfIsRightDerivedFunctorComp).
We may say that this is the comparison morphism for the
composition of right derived functors, even though the
definition only assumes that RF₁₃ is a right derived functor.
(In applications, both RF₁₂ and RF₂₃ would usually
be derived functors as well.)
The comparison morphism for the composition of right derived functors.
Equations
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