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LeanPool.JacobianDiffgeo.Finiteness.Chain

ShrinkChain: Forster's four-level shrinking chain (finiteness-and-chi) #

Unit: finiteness-and-chi (docs/design/finiteness-and-chi.md D3, Β§4.2, proof plan Β§6.4).

ShrinkChain X packages Forster's π”š ⋐ 𝔙 ⋐ π”˜ ⋐ π”˜* same-index-set shrinking chain (D3): U* chart disks (Leray-good), U the level whose closure sits inside U*, V the Montel-compact middle level, W the coboundary level whose closure sits inside V. All four induced FinCover ⊀s share the same index set, so every refinement map between them is Ο„ = id (ref_star_U/ref_star_V/ref_star_W/ref_U_V/ref_V_W/ref_U_W) β€” no Ο„-plumbing ever enters the norm layer.

Existence (ShrinkChain.nonempty) iterates the cech exists_chartDisk_closure_basis pattern four times per point (chart disk ⋐ level 1 ⋐ level 2 ⋐ level 3), then extracts a finite subcover of the innermost level W, reindexed by Finset.equivFin exactly as Cech.Covers's exists_good_refinement_closure does.

Also provides the Banach cochain layer at one level P ∈ {U, V, W}: NC0/NC1 (finite Pis of BddHoloOn), deltaCLM (the 0-to-1 coboundary, Cech's d0 transposed to the norm layer), NZ1 (bounded cocycles, packaged as ContinuousLinearMap.ker of an internal d1NC β€” closed and complete "for free", no hand-rolled pointwise-condition closedness proof needed), resNC0/resNC1 (restriction CLMs between same-index levels), the cocycle-relation workhorse NZ1.rel_res (mirrors Cech.Refinement's Z1.rel_res), resNC1_mapsTo_NZ1 (mirrors resC1_mem_Z1), and resZ (restriction of bounded cocycles, via ContinuousLinearMap.codRestrict).

Finally, Forster's 14.6(b) Banach geometry (Β§4.2, Β§5 step 1): tradeDefect (the defect CLM (ΞΆ, ΞΎ, Ξ·) ↦ ΞΆ|π”š βˆ’ ΞΎ|π”š βˆ’ Ξ΄π”š Ξ· on ZΒΉ(π”˜) Γ— ZΒΉ(𝔙) Γ— C⁰(π”š)), tradeSpace (Forster's subspace L βŠ† ZΒΉ(π”˜) Γ— ZΒΉ(𝔙) Γ— C⁰(π”š), its ContinuousLinearMap.ker β€” complete for free), the membership unfolders mem_tradeSpace_iff/mem_tradeSpace_iff_eq, and the two Schwartz-cospan projections tradePi (Ο€ = prβ‚‚, the leg TradeBounded.lean proves surjective) and tradeCompact (v = res_UV ∘ pr₁, the Montel-compact leg), plus registered instance shortcuts on β†₯(NZ1 T P)/β†₯(tradeSpace T) that make the surrounding instance searches reliable (see the note above NZ1's instances and the resolution note at the end of this file β€” the former TODO(blocker) is RESOLVED). Still deferred (NOT instance-blocked, just not built here): the two IsCompactOperator assembly lemmas of design Β§4.4 (isCompactOperator_resZ_UV, isCompactOperator_tradeCompact) β€” see the end-of-file note. Nothing here uses the forbidden tactic.

Forster's π”š ⋐ 𝔙 ⋐ π”˜ ⋐ π”˜* with π”˜* chart disks; same index set (D3).

Instances For
    theorem RS.Finiteness.ShrinkChain.W_subset_V {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] (T : ShrinkChain X) (i : Fin T.n) :
    ↑(T.W i) βŠ† ↑(T.V i)
    theorem RS.Finiteness.ShrinkChain.V_subset_U {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] (T : ShrinkChain X) (i : Fin T.n) :
    ↑(T.V i) βŠ† ↑(T.U i)
    theorem RS.Finiteness.ShrinkChain.U_subset_Ustar {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] (T : ShrinkChain X) (i : Fin T.n) :
    ↑(T.U i) βŠ† ↑(T.Ustar i)

    Opens-level ≀ forms of the chain inclusions β€” the shapes restrictCLM/resNC1/resZ consume (definitionally the same statements as the Set-level _subset_ lemmas above).

    theorem RS.Finiteness.ShrinkChain.covers_V {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] (T : ShrinkChain X) (x : X) :
    βˆƒ (i : Fin T.n), x ∈ T.V i
    theorem RS.Finiteness.ShrinkChain.covers_U {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] (T : ShrinkChain X) (x : X) :
    βˆƒ (i : Fin T.n), x ∈ T.U i
    theorem RS.Finiteness.ShrinkChain.covers_Ustar {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] (T : ShrinkChain X) (x : X) :
    βˆƒ (i : Fin T.n), x ∈ T.Ustar i
    @[reducible]

    The four FinCover ⊀s induced by a ShrinkChain. Reducible: their fields must unfold at implicit transparency, or applications like C1 D T.coverW are not type-correct there and every rewrite in such a goal fails.

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    • T.coverW = { n := T.n, U := T.W, le_base := β‹―, covers := β‹― }
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      @[reducible]

      The cover of X by the V-level opens.

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      • T.coverV = { n := T.n, U := T.V, le_base := β‹―, covers := β‹― }
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        @[reducible]

        The cover of X by the U-level opens.

        Equations
        • T.coverU = { n := T.n, U := T.U, le_base := β‹―, covers := β‹― }
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          @[reducible]

          The cover of X by the outermost Ustar-level opens.

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            Existence of a ShrinkChain (Β§6.4): iterate the cech chart-disk-with-compact-closure basis four times per point, then extract a finite subcover of the innermost level.

            Banach cochain layer at a level P ∈ {U, V, W} #

            @[reducible, inline]

            0-cochains at level P (a finite Pi of BddHoloOns).

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              @[reducible, inline]

              1-cochains at level P (full product over ordered pairs, no i < j convention β€” matches cech's D5 convention).

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                (δ⁰f)_{ij} = f_j βˆ’ f_i (after restriction to P i βŠ“ P j); the Banach-layer analogue of Cech.d0.

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                  @[simp]
                  theorem RS.Finiteness.deltaCLM_apply {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (P : Fin T.n β†’ TopologicalSpace.Opens X) (f : NC0 T P) (p : Fin T.n Γ— Fin T.n) :
                  (deltaCLM T P) f p = (restrictCLM β‹―) (f p.2) - (restrictCLM β‹―) (f p.1)
                  noncomputable def RS.Finiteness.d1NC {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (P : Fin T.n β†’ TopologicalSpace.Opens X) :
                  NC1 T P β†’L[β„‚] (t : Fin T.n Γ— Fin T.n Γ— Fin T.n) β†’ β†₯(BddHoloOn (P t.1 βŠ“ P t.2.1 βŠ“ P t.2.2))

                  The 1-to-2-cochain coboundary at level P, purely internal (used only to package NZ1 as a continuous-kernel submodule β€” no NC2 is ever exported).

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                    @[simp]
                    theorem RS.Finiteness.d1NC_apply {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (P : Fin T.n β†’ TopologicalSpace.Opens X) (f : NC1 T P) (t : Fin T.n Γ— Fin T.n Γ— Fin T.n) :
                    (d1NC T P) f t = (restrictCLM β‹―) (f (t.2.1, t.2.2)) - (restrictCLM β‹―) (f (t.1, t.2.2)) + (restrictCLM β‹―) (f (t.1, t.2.1))

                    Bounded cocycles: the kernel of d1NC, a closed submodule (ContinuousLinearMap.ker) β€” Banach for free (ContinuousLinearMap.completeSpace_ker), no hand-rolled pointwise-condition closedness proof needed.

                    The norm-bounded cocycles at level P: the kernel of the bounded coboundary d1NC.

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                      theorem RS.Finiteness.mem_NZ1_iff {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (P : Fin T.n β†’ TopologicalSpace.Opens X) (f : NC1 T P) :
                      f ∈ NZ1 T P ↔ βˆ€ (t : Fin T.n Γ— Fin T.n Γ— Fin T.n), (d1NC T P) f t = 0
                      theorem RS.Finiteness.NZ1.rel_res {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (P : Fin T.n β†’ TopologicalSpace.Opens X) {f : NC1 T P} (hf : f ∈ NZ1 T P) (a b c : Fin T.n) {W : TopologicalSpace.Opens X} (h : W ≀ P a βŠ“ P b βŠ“ P c) (hbc : W ≀ P b βŠ“ P c) (hac : W ≀ P a βŠ“ P c) (hab : W ≀ P a βŠ“ P b) :
                      (restrictCLM hbc) (f (b, c)) - (restrictCLM hac) (f (a, c)) + (restrictCLM hab) (f (a, b)) = 0

                      The cocycle-relation workhorse (mirrors Cech.Refinement's Z1.rel_res): any cocycle-relation triple, restricted to any smaller open W (via arbitrary β€” by proof irrelevance, any β€” witnessing inequalities).

                      noncomputable def RS.Finiteness.resNC0 {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (P P' : Fin T.n β†’ TopologicalSpace.Opens X) (h : βˆ€ (i : Fin T.n), P' i ≀ P i) :

                      Restriction of 0-cochains along a same-index shrinking P' ≀ P.

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                        noncomputable def RS.Finiteness.resNC1 {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (P P' : Fin T.n β†’ TopologicalSpace.Opens X) (h : βˆ€ (i : Fin T.n), P' i ≀ P i) :

                        Restriction of 1-cochains along a same-index shrinking P' ≀ P.

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                          @[simp]
                          theorem RS.Finiteness.resNC1_apply {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (P P' : Fin T.n β†’ TopologicalSpace.Opens X) (h : βˆ€ (i : Fin T.n), P' i ≀ P i) (f : NC1 T P) (p : Fin T.n Γ— Fin T.n) :
                          (resNC1 T P P' h) f p = (restrictCLM β‹―) (f p)
                          theorem RS.Finiteness.resNC1_mapsTo_NZ1 {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (P P' : Fin T.n β†’ TopologicalSpace.Opens X) (h : βˆ€ (i : Fin T.n), P' i ≀ P i) {f : NC1 T P} (hf : f ∈ NZ1 T P) :
                          (resNC1 T P P' h) f ∈ NZ1 T P'

                          Restriction takes bounded cocycles to bounded cocycles (naturality of d1NC, via the NZ1.rel_res workhorse β€” mirrors Cech.Refinement's resC1_mem_Z1).

                          noncomputable def RS.Finiteness.resZ {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (P P' : Fin T.n β†’ TopologicalSpace.Opens X) (h : βˆ€ (i : Fin T.n), P' i ≀ P i) :
                          β†₯(NZ1 T P) β†’L[β„‚] β†₯(NZ1 T P')

                          Restriction of bounded cocycles between same-index levels.

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                            Forster 14.6(b): the trade subspace L and its two Schwartz-cospan projections #

                            Forster 14.6(b)'s defect map (ΞΆ, ΞΎ, Ξ·) ↦ ΞΆ|π”š βˆ’ ΞΎ|π”š βˆ’ Ξ΄π”š Ξ· on the triple product ZΒΉ(π”˜) Γ— ZΒΉ(𝔙) Γ— C⁰(π”š) (Β§4.2/Β§5 step 1); its kernel is Forster's subspace L (tradeSpace).

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                              @[simp]
                              theorem RS.Finiteness.tradeDefect_apply {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (x : β†₯(NZ1 T T.U) Γ— β†₯(NZ1 T T.V) Γ— NC0 T T.W) (p : Fin T.n Γ— Fin T.n) :
                              (tradeDefect T) x p = (restrictCLM β‹―) (↑x.1 p) - (restrictCLM β‹―) (↑x.2.1 p) - ((restrictCLM β‹―) (x.2.2 p.2) - (restrictCLM β‹―) (x.2.2 p.1))

                              Forster's subspace L (14.6(b)): triples (ΞΆ, ΞΎ, Ξ·) with ΞΆ = ΞΎ + δη on π”š, packaged as ContinuousLinearMap.ker (closed, hence complete for free).

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                                theorem RS.Finiteness.mem_tradeSpace_iff {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (x : β†₯(NZ1 T T.U) Γ— β†₯(NZ1 T T.V) Γ— NC0 T T.W) :
                                x ∈ tradeSpace T ↔ βˆ€ (p : Fin T.n Γ— Fin T.n), (tradeDefect T) x p = 0
                                theorem RS.Finiteness.mem_tradeSpace_iff_eq {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (x : β†₯(NZ1 T T.U) Γ— β†₯(NZ1 T T.V) Γ— NC0 T T.W) :
                                x ∈ tradeSpace T ↔ βˆ€ (p : Fin T.n Γ— Fin T.n), (restrictCLM β‹―) (↑x.1 p) = (restrictCLM β‹―) (↑x.2.1 p) + ((restrictCLM β‹―) (x.2.2 p.2) - (restrictCLM β‹―) (x.2.2 p.1))

                                Membership in L, rearranged to Forster's ΞΆ = ΞΎ + δη shape on each π”š-pair (the form TradeBounded.lean's Β§5 steps 2/6/8 consume).

                                The surjective leg Ο€ : L β†’L ZΒΉ(𝔙), (ΞΆ, ΞΎ, Ξ·) ↦ ΞΎ (14.6(b)'s projection; surjectivity = the qualitative trade, proved in TradeBounded.lean as tradePi_surjective; the norm constant of 14.6(b) is recovered inside schwartz_finite_cospan by exists_preimage_norm_le β€” design Β§5 step 7).

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                                  The compact leg v : L β†’L ZΒΉ(𝔙), (ΞΆ, ΞΎ, Ξ·) ↦ ΞΆ|𝔙 (compactness = Montel, assembled from isCompactOperator_restrictCLM β€” deferred, see the end-of-file note).

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                                    @[simp]
                                    theorem RS.Finiteness.tradeCompact_apply {X : Type u_1} [TopologicalSpace X] [ChartedSpace β„‚ X] [IsManifold (modelWithCornersSelf β„‚ β„‚) ⊀ X] (T : ShrinkChain X) (x : β†₯(tradeSpace T)) :
                                    (tradeCompact T) x = (resZ T T.U T.V β‹―) (↑x).1