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TauCeti.Algebra.Homology.AInfinity.Module.Right.Hom.Homotopy

Homotopies of morphisms of right A-infinity modules #

Let f g : M ⟶ N be morphisms of right A∞ modules over a fixed algebra. A homotopy from f to g is a degree--1 morphism H of their cofree bar comodules satisfying

F - G = b_N H + H b_M.

The comodule morphism H is determined by its suspended Taylor map, obtained by applying the coalgebra counit. The homotopy equation can likewise be checked after applying the counit. Its component with no algebra inputs is an ordinary chain homotopy between the linear parts of f and g; consequently homotopic module morphisms induce the same map on cohomology and are quasi-isomorphisms together.

Homotopies are reflexive, symmetric, and transitive, and they are preserved by composition with module morphisms on either side.

Main definitions #

References #

structure TauCeti.AInfinityRightModuleHom.Homotopy {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} (f g : AInfinityRightModuleHom MM NN) :
Type (max (max (max uA uM) uN) uR)

A homotopy from f to g is a degree--1 morphism of their cofree bar comodules whose commutator with the module bar differentials is F - G.

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    @[reducible, inline]
    abbrev TauCeti.AInfinityRightModuleHom.Homotopy.barMap {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) :

    The underlying linear map of the bar-comodule homotopy.

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      theorem TauCeti.AInfinityRightModuleHom.Homotopy.barMap_sub_barMap_apply {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) (z : TensorProduct R M (TensorWords R A)) :

      The homotopy equation, applied to one bar-comodule element.

      noncomputable def TauCeti.AInfinityRightModuleHom.Homotopy.taylor {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) :

      The suspended Taylor map of a module homotopy, obtained by applying the coalgebra counit.

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        The Taylor map of a homotopy lowers suspended degree by one.

        The bar homotopy is the cofree lift of its Taylor map.

        theorem TauCeti.AInfinityRightModuleHom.Homotopy.ext {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} {h h' : f.Homotopy g} (e : h.taylor = h'.taylor) :
        h = h'

        Homotopies between fixed morphisms are determined by their Taylor maps.

        theorem TauCeti.AInfinityRightModuleHom.Homotopy.ext_iff {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} {h h' : f.Homotopy g} :
        h = h' ↔ h.taylor = h'.taylor

        The suspended component equation of a module homotopy.

        Construct a homotopy from a degree--1 comodule morphism satisfying the suspended component equation.

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          The unary component #

          noncomputable def TauCeti.AInfinityRightModuleHom.Homotopy.linearHomotopy {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) :

          The unary component of a module homotopy, evaluated on the empty algebra word.

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            @[simp]
            theorem TauCeti.AInfinityRightModuleHom.Homotopy.linearHomotopy_apply {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) (x : M) :
            @[simp]
            theorem TauCeti.AInfinityRightModuleHom.Homotopy.barMap_tmul_one {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) (x : M) :

            A bar homotopy sends an empty algebra word to the empty word multiplied by its unary component.

            theorem TauCeti.AInfinityRightModuleHom.Homotopy.linearHomotopy_mem {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) {x : M} {p : ℤ} (hx : x ∈ MM.grading.piece p) :

            The unary component of a module homotopy lowers the unsuspended degree by one.

            The unary component is a chain homotopy between the linear parts.

            Cohomology #

            Homotopic module morphisms induce the same map on unary cohomology.

            Homotopic module morphisms are quasi-isomorphisms together.

            Equivalence and composition laws #

            noncomputable def TauCeti.AInfinityRightModuleHom.Homotopy.refl {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} (f : AInfinityRightModuleHom MM NN) :

            The zero homotopy from a module morphism to itself.

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              @[simp]
              theorem TauCeti.AInfinityRightModuleHom.Homotopy.barMap_refl {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} (f : AInfinityRightModuleHom MM NN) :
              (refl f).barMap = 0
              @[simp]
              theorem TauCeti.AInfinityRightModuleHom.Homotopy.taylor_refl {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} (f : AInfinityRightModuleHom MM NN) :
              (refl f).taylor = 0
              noncomputable def TauCeti.AInfinityRightModuleHom.Homotopy.symm {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) :

              Reverse a module homotopy.

              Equations
              • h.symm = { barHomotopy := -1 • h.barHomotopy, isHomogeneous_barHomotopy := ⋯, barMap_sub_barMap := ⋯ }
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                @[simp]
                theorem TauCeti.AInfinityRightModuleHom.Homotopy.barMap_symm {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) :
                noncomputable def TauCeti.AInfinityRightModuleHom.Homotopy.trans {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g k : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) (h' : g.Homotopy k) :

                Concatenate two module homotopies.

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                  @[simp]
                  theorem TauCeti.AInfinityRightModuleHom.Homotopy.barMap_trans {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g k : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) (h' : g.Homotopy k) :
                  (h.trans h').barMap = h.barMap + h'.barMap
                  noncomputable def TauCeti.AInfinityRightModuleHom.Homotopy.compRight {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} {P : Type uP} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] [AddCommGroup P] [Module R P] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {PP : AInfinityRightModule AA P} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) (l : AInfinityRightModuleHom NN PP) :
                  (l.comp f).Homotopy (l.comp g)

                  Postcomposition of a homotopy by a module morphism.

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                    @[simp]
                    theorem TauCeti.AInfinityRightModuleHom.Homotopy.barMap_compRight {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} {P : Type uP} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] [AddCommGroup P] [Module R P] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {PP : AInfinityRightModule AA P} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) (l : AInfinityRightModuleHom NN PP) :
                    theorem TauCeti.AInfinityRightModuleHom.Homotopy.taylor_compRight {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {M : Type uM} {N : Type uN} {P : Type uP} [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] [AddCommGroup P] [Module R P] {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {PP : AInfinityRightModule AA P} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) (l : AInfinityRightModuleHom NN PP) :

                    Postcomposition applies the Taylor map of the outer morphism to the bar homotopy.

                    noncomputable def TauCeti.AInfinityRightModuleHom.Homotopy.compLeft {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {L : Type uL} {M : Type uM} {N : Type uN} [AddCommGroup L] [Module R L] [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {LL : AInfinityRightModule AA L} {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) (l : AInfinityRightModuleHom LL MM) :
                    (f.comp l).Homotopy (g.comp l)

                    Precomposition of a homotopy by a module morphism.

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                      @[simp]
                      theorem TauCeti.AInfinityRightModuleHom.Homotopy.barMap_compLeft {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {L : Type uL} {M : Type uM} {N : Type uN} [AddCommGroup L] [Module R L] [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {LL : AInfinityRightModule AA L} {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) (l : AInfinityRightModuleHom LL MM) :
                      theorem TauCeti.AInfinityRightModuleHom.Homotopy.taylor_compLeft {R : Type uR} {A : Type uA} [CommRing R] [AddCommGroup A] [Module R A] {AA : AInfinityAlgebra R A} {L : Type uL} {M : Type uM} {N : Type uN} [AddCommGroup L] [Module R L] [AddCommGroup M] [Module R M] [AddCommGroup N] [Module R N] {LL : AInfinityRightModule AA L} {MM : AInfinityRightModule AA M} {NN : AInfinityRightModule AA N} {f g : AInfinityRightModuleHom MM NN} (h : f.Homotopy g) (l : AInfinityRightModuleHom LL MM) :

                      Precomposition applies the Taylor map of the homotopy after the inner bar map.