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Mathlib.Algebra.Homology.Embedding.TruncGEHomology

The homology of a canonical truncation #

Given an embedding of complex shapes e : Embedding c c', we shall relate the homology of K : HomologicalComplex C c' and of K.truncGE e : HomologicalComplex C c' (TODO).

So far, we only compute the homology of K.truncGE' e : HomologicalComplex C c.

theorem HomologicalComplex.truncGE'.hasHomology_sc'_of_not_mem_boundary {ι : Type u_1} {ι' : Type u_2} {c : ComplexShape ι} {c' : ComplexShape ι'} {C : Type u_3} [CategoryTheory.Category.{u_4, u_3} C] [CategoryTheory.Limits.HasZeroMorphisms C] (K : HomologicalComplex C c') (e : c.Embedding c') [e.IsTruncGE] [∀ (i' : ι'), K.HasHomology i'] (i j k : ι) (hi : c.prev j = i) (hk : c.next j = k) (hj : ¬e.BoundaryGE j) :
((K.truncGE' e).sc' i j k).HasHomology
theorem HomologicalComplex.truncGE'.hasHomology_of_not_mem_boundary {ι : Type u_1} {ι' : Type u_2} {c : ComplexShape ι} {c' : ComplexShape ι'} {C : Type u_3} [CategoryTheory.Category.{u_4, u_3} C] [CategoryTheory.Limits.HasZeroMorphisms C] (K : HomologicalComplex C c') (e : c.Embedding c') [e.IsTruncGE] [∀ (i' : ι'), K.HasHomology i'] (j : ι) (hj : ¬e.BoundaryGE j) :
(K.truncGE' e).HasHomology j
theorem HomologicalComplex.truncGE'.quasiIsoAt_restrictionToTruncGE'_f {ι : Type u_1} {ι' : Type u_2} {c : ComplexShape ι} {c' : ComplexShape ι'} {C : Type u_3} [CategoryTheory.Category.{u_4, u_3} C] [CategoryTheory.Limits.HasZeroMorphisms C] (K : HomologicalComplex C c') (e : c.Embedding c') [e.IsTruncGE] [∀ (i' : ι'), K.HasHomology i'] (j : ι) (hj : ¬e.BoundaryGE j) [(K.restriction e).HasHomology j] [(K.truncGE' e).HasHomology j] :
QuasiIsoAt (K.restrictionToTruncGE' e) j
theorem HomologicalComplex.truncGE'.homologyι_truncGE'XIsoOpcycles_inv_d {ι : Type u_1} {ι' : Type u_2} {c : ComplexShape ι} {c' : ComplexShape ι'} {C : Type u_3} [CategoryTheory.Category.{u_4, u_3} C] [CategoryTheory.Limits.HasZeroMorphisms C] (K : HomologicalComplex C c') (e : c.Embedding c') [e.IsTruncGE] [∀ (i' : ι'), K.HasHomology i'] (j k : ι) {j' : ι'} (hj' : e.f j = j') (hj : e.BoundaryGE j) :
CategoryTheory.CategoryStruct.comp (CategoryTheory.CategoryStruct.comp (K.homologyι j') (K.truncGE'XIsoOpcycles e hj' hj).inv) ((K.truncGE' e).d j k) = 0
noncomputable def HomologicalComplex.truncGE'.isLimitKernelFork {ι : Type u_1} {ι' : Type u_2} {c : ComplexShape ι} {c' : ComplexShape ι'} {C : Type u_3} [CategoryTheory.Category.{u_4, u_3} C] [CategoryTheory.Limits.HasZeroMorphisms C] (K : HomologicalComplex C c') (e : c.Embedding c') [e.IsTruncGE] [∀ (i' : ι'), K.HasHomology i'] (j k : ι) (hk : c.next j = k) {j' : ι'} (hj' : e.f j = j') (hj : e.BoundaryGE j) :

Auxiliary definition for truncGE'.homologyData.

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    noncomputable def HomologicalComplex.truncGE'.homologyData {ι : Type u_1} {ι' : Type u_2} {c : ComplexShape ι} {c' : ComplexShape ι'} {C : Type u_3} [CategoryTheory.Category.{u_4, u_3} C] [CategoryTheory.Limits.HasZeroMorphisms C] (K : HomologicalComplex C c') (e : c.Embedding c') [e.IsTruncGE] [∀ (i' : ι'), K.HasHomology i'] (i j k : ι) (hk : c.next j = k) {j' : ι'} (hj' : e.f j = j') (hj : e.BoundaryGE j) :
    ((K.truncGE' e).sc' i j k).HomologyData

    When j is at the boundary of the embedding e of complex shapes, this is a homology data for K.truncGE' e in degree j: the homology is given by K.homology j' where e.f j = j'.

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      @[simp]
      theorem HomologicalComplex.truncGE'.homologyData_right_g' {ι : Type u_1} {ι' : Type u_2} {c : ComplexShape ι} {c' : ComplexShape ι'} {C : Type u_3} [CategoryTheory.Category.{u_4, u_3} C] [CategoryTheory.Limits.HasZeroMorphisms C] (K : HomologicalComplex C c') (e : c.Embedding c') [e.IsTruncGE] [∀ (i' : ι'), K.HasHomology i'] (i j k : ι) (hk : c.next j = k) {j' : ι'} (hj' : e.f j = j') (hj : e.BoundaryGE j) :
      (homologyData K e i j k hk hj' hj).right.g' = (K.truncGE' e).d j k

      Computation of the right.g' field of truncGE'.homologyData K e i j k hk hj' hj.

      instance HomologicalComplex.truncGE'.truncGE'_hasHomology {ι : Type u_1} {ι' : Type u_2} {c : ComplexShape ι} {c' : ComplexShape ι'} {C : Type u_3} [CategoryTheory.Category.{u_4, u_3} C] [CategoryTheory.Limits.HasZeroMorphisms C] (K : HomologicalComplex C c') (e : c.Embedding c') [e.IsTruncGE] [∀ (i' : ι'), K.HasHomology i'] (i : ι) :
      (K.truncGE' e).HasHomology i