import OAI.Combinatorics.CompleteCrossing.Assembly import OAI.Combinatorics.Crossing.PolygonalNormalization import OAI.Combinatorics.Crossing.ProperCrossingLocality import OAI.Combinatorics.Crossing.ProperSegmentCrossing namespace OAI /-! Admissible polygonal replacement and retention of crossing counts. -/ section /-! Inside a crossing disk, an assembled edge has exactly its assigned straight chord trace. -/ noncomputable section open Zarankiewicz variable {Vertex Edge : Type} {graph : Paper170.Graph Vertex Edge} namespace Paper170Geometry.DrawingPassages variable {D : FiniteIntersectionDrawing graph} def crossingDisk (C : DrawingPassages D) (p : C.InnerIndex) : Set Plane := {x | squaredLength (x-(C.innerMark p).val) < C.radius^2} theorem crossingDisk_isOpen (C : DrawingPassages D) (p : C.InnerIndex) : IsOpen (C.crossingDisk p) := by apply isOpen_lt _ continuous_const unfold squaredLength fun_prop theorem crossingDisk_subset_closed (C : DrawingPassages D) (p : C.InnerIndex) : C.crossingDisk p ⊆ closedRoundDisk (C.innerMark p).val C.radius := by intro x hx exact (show squaredLength (x-(C.innerMark p).val) < C.radius^2 from hx).le theorem crossingDisk_disjoint_vertex_disk (C : DrawingPassages D) (p : C.InnerIndex) (j : Vertex) : Disjoint (C.crossingDisk p) (closedRoundDisk (D.vertex j) C.radius) := by have hn : C.innerMark p ≠ C.vertexMark j := by intro he exact crossing_not_vertex D (C.innerMark p).val (C.innerMark_is_crossing p) j (congrArg Subtype.val he) exact (C.disks_disjoint _ _ hn).mono (C.crossingDisk_subset_closed p) Set.Subset.rfl theorem crossingChord_openTrace_iff (C : DrawingPassages D) (p : C.InnerIndex) (x : Plane) (hx : x ∈ C.crossingDisk p) : x ∈ Set.range (C.crossingChord p) ↔ x ∈ openSegmentTrace (C.portPoint (C.incomingPort p)) (C.portPoint (C.outgoingPort p)) := by constructor · rintro ⟨t,ht⟩ have ht0 : t ≠ 0 := by intro he subst t rw [Path.source] at ht change squaredLength (x-(C.innerMark p).val) < C.radius^2 at hx rw [← ht,C.incomingPoint_on_circle] at hx exact lt_irrefl _ hx have ht1 : t ≠ 1 := by intro he subst t rw [Path.target] at ht change squaredLength (x-(C.innerMark p).val) < C.radius^2 at hx rw [← ht,C.outgoingPoint_on_circle] at hx exact lt_irrefl _ hx refine ⟨t.val,⟨?_,?_⟩,?_⟩ · exact lt_of_le_of_ne t.property.1 (fun he => ht0 (Subtype.ext he.symm)) · exact lt_of_le_of_ne t.property.2 (fun he => ht1 (Subtype.ext he)) · simpa only [crossingChord,Path.segment_apply,AffineMap.lineMap_apply_module,segmentPoint] using ht · rintro ⟨t,ht,he⟩ refine ⟨⟨t,ht.1.le,ht.2.le⟩,?_⟩ simpa only [crossingChord,Path.segment_apply,AffineMap.lineMap_apply_module,segmentPoint] using he end DrawingPassages namespace PolygonalExterior variable {D : FiniteIntersectionDrawing graph} {C : DrawingPassages D} theorem assembled_range_in_crossingDisk (E : PolygonalExterior C) (v : Vertex → Plane) (hv : ∀ j, squaredLength (v j-D.vertex j) < C.radius^2) (p : C.InnerIndex) (x : Plane) (hx : x ∈ C.crossingDisk p) : x ∈ Set.range (E.assembledEdge v p.1) ↔ x ∈ Set.range (C.crossingChord p) := by constructor · intro he rcases (E.assembledEdge_range_iff v p.1 x).mp he with (he | ⟨i,hi,he⟩ | ⟨q,hq,he⟩) | he · exact False.elim (Set.disjoint_left.mp (C.crossingDisk_disjoint_vertex_disk p _) hx (C.vertex_spoke_range_in_disk v hv _ (C.startPortAt p.1) he)) · obtain ⟨t,rfl⟩ := he exact False.elim (hx.not_ge (E.outside_open_disks i t (C.innerMark p))) · have hm : C.innerMark q=C.innerMark p := by by_contra hn exact Set.disjoint_left.mp (C.disks_disjoint _ _ hn) (C.crossingChord_range_subset_disk q he) (C.crossingDisk_subset_closed p hx) have hqp := C.innerIndex_eq_of_edge_mark q p hq hm exact hqp ▸ he · rw [endSpoke_range] at he exact False.elim (Set.disjoint_left.mp (C.crossingDisk_disjoint_vertex_disk p _) hx (C.vertex_spoke_range_in_disk v hv _ (C.endPortAt p.1) he)) · intro he apply (E.assembledEdge_range_iff v p.1 x).mpr exact Or.inl (Or.inr (Or.inr ⟨p,rfl,he⟩)) theorem assembled_trace_in_crossingDisk (E : PolygonalExterior C) (v : Vertex → Plane) (hvinj : Function.Injective v) (hv : ∀ j, squaredLength (v j-D.vertex j) < C.radius^2) (p : C.InnerIndex) (x : Plane) (hx : x ∈ C.crossingDisk p) : x ∈ Paper170.edgeInterior (E.assembledDrawing v hvinj hv) p.1 ↔ x ∈ openSegmentTrace (C.portPoint (C.incomingPort p)) (C.portPoint (C.outgoingPort p)) := by have havoid : ∀ j, x ≠ v j := by intro j he exact Set.disjoint_left.mp (C.crossingDisk_disjoint_vertex_disk p j) hx (he.symm ▸ (hv j).le) rw [← C.crossingChord_openTrace_iff p x hx,← E.assembled_range_in_crossingDisk v hv p x hx] constructor · rintro ⟨t,ht,he⟩ exact ⟨t,he⟩ · rintro ⟨t,he⟩ have ht0 : t ≠ 0 := by intro ht subst t rw [Path.source] at he exact havoid _ he.symm have ht1 : t ≠ 1 := by intro ht subst t rw [Path.target] at he exact havoid _ he.symm exact ⟨t,⟨lt_of_le_of_ne (show 0 ≤ t from t.property.1) (Ne.symm ht0), lt_of_le_of_ne (show t ≤ 1 from t.property.2) ht1⟩,he⟩ end PolygonalExterior end Paper170Geometry end end section /-! All admissibility conditions and spatial crossing-count nonincrease for the assembled drawing. -/ noncomputable section open Zarankiewicz variable {Vertex Edge : Type} {graph : Paper170.Graph Vertex Edge} namespace Paper170Geometry.DrawingPassages variable {D : FiniteIntersectionDrawing graph} theorem crossingChord_meeting_proper (C : DrawingPassages D) (p q : C.InnerIndex) (hpq : p ≠ q) (x : Plane) (hxp : x ∈ Set.range (C.crossingChord p)) (hxq : x ∈ Set.range (C.crossingChord q)) : x ∈ C.crossingDisk p ∧ Paper170.ProperCrossing (openSegmentTrace (C.portPoint (C.incomingPort p)) (C.portPoint (C.outgoingPort p))) (openSegmentTrace (C.portPoint (C.incomingPort q)) (C.portPoint (C.outgoingPort q))) x := by have hm := C.chord_meeting_marks_eq p q hxp hxq obtain ⟨s,hs⟩ := hxp obtain ⟨t,ht⟩ := hxq have hst : segmentPoint (C.portPoint (C.incomingPort p)) (C.portPoint (C.outgoingPort p)) s.val = segmentPoint (C.portPoint (C.incomingPort q)) (C.portPoint (C.outgoingPort q)) t.val := by simpa only [crossingChord,Path.segment_apply,AffineMap.lineMap_apply_module,segmentPoint] using hs.trans ht.symm obtain ⟨hd,hsi,hti⟩ := C.crossing_chords_transverse_at_mark p q hpq hm s.val s.property t.val t.property hst refine ⟨?_,?_⟩ · rw [← hs] exact C.crossingChord_interior_in_disk p s hsi · constructor apply properCrossing_openSegments _ _ _ _ x hd · exact ⟨s.val,hsi,by simpa only [crossingChord,Path.segment_apply,AffineMap.lineMap_apply_module,segmentPoint] using hs⟩ · exact ⟨t.val,hti,by simpa only [crossingChord,Path.segment_apply,AffineMap.lineMap_apply_module,segmentPoint] using ht⟩ end DrawingPassages namespace PolygonalExterior variable {D : FiniteIntersectionDrawing graph} {C : DrawingPassages D} theorem assembled_crossings_proper (E : PolygonalExterior C) (v : Vertex → Plane) (hvinj : Function.Injective v) (hv : ∀ j, squaredLength (v j-D.vertex j) < C.radius^2) (hdet : ∀ j (p q : C.PortsAt (C.vertexMark j)), p ≠ q → det2 (C.portPoint p.val-v j) (C.portPoint q.val-v j) ≠ 0) (e f : Edge) (hef : e ≠ f) (x : Plane) (hx : x ∈ Paper170.edgeInterior (E.assembledDrawing v hvinj hv) e) (hy : x ∈ Paper170.edgeInterior (E.assembledDrawing v hvinj hv) f) : Paper170.ProperCrossing (Paper170.edgeInterior (E.assembledDrawing v hvinj hv) e) (Paper170.edgeInterior (E.assembledDrawing v hvinj hv) f) x := by obtain ⟨s,hs,he⟩ := hx obtain ⟨t,ht,hf⟩ := hy obtain ⟨p,q,hp,hq,hxp,hxq⟩ := E.assembled_meeting_chords v hv hdet e f hef x (fun j heq => E.assembledEdge_interior_avoids_vertices v hv e s hs j (he.trans heq)) ⟨s,he⟩ ⟨t,hf⟩ have hpq : p ≠ q := fun heq => hef (hp.symm.trans ((congrArg Sigma.fst heq).trans hq)) have hm := C.chord_meeting_marks_eq p q hxp hxq obtain ⟨hxin,hproper⟩ := C.crossingChord_meeting_proper p q hpq x hxp hxq constructor apply properCrossing_of_local_eq _ _ _ _ x hproper.chart_exists (C.crossingDisk p) (C.crossingDisk_isOpen p) hxin · intro z hz simpa only [hp] using (E.assembled_trace_in_crossingDisk v hvinj hv p z hz).symm · intro z hz have hzq : z ∈ C.crossingDisk q := by change squaredLength (z-(C.innerMark q).val) < C.radius^2 rw [← hm] exact hz simpa only [hq] using (E.assembled_trace_in_crossingDisk v hvinj hv q z hzq).symm def assembledAdmissible (E : PolygonalExterior C) (v : Vertex → Plane) (hvinj : Function.Injective v) (hv : ∀ j, squaredLength (v j-D.vertex j) < C.radius^2) (hdet : ∀ j (p q : C.PortsAt (C.vertexMark j)), p ≠ q → det2 (C.portPoint p.val-v j) (C.portPoint q.val-v j) ≠ 0) : Paper170.AdmissibleDrawing graph where toContinuousDrawing := E.assembledDrawing v hvinj hv crossings_finite := E.assembled_crossings_finite v hvinj hv hdet crossings_proper := E.assembled_crossings_proper v hvinj hv hdet no_triples := E.assembled_no_triples v hvinj hv hdet theorem assembled_crossingCount_le (E : PolygonalExterior C) (v : Vertex → Plane) (hvinj : Function.Injective v) (hv : ∀ j, squaredLength (v j-D.vertex j) < C.radius^2) (hdet : ∀ j (p q : C.PortsAt (C.vertexMark j)), p ≠ q → det2 (C.portPoint p.val-v j) (C.portPoint q.val-v j) ≠ 0) : Paper170.crossingCount (E.assembledAdmissible v hvinj hv hdet) ≤ finiteCrossingCount D := by have h := Set.ncard_le_ncard (E.assembled_crossings_subset v hvinj hv hdet) C.chordCrossings_finite have hcount : Paper170.crossingCount (E.assembledAdmissible v hvinj hv hdet)= (Paper170.crossingPoints (E.assembledDrawing v hvinj hv)).ncard := by rw [Set.ncard_eq_toFinset_card _ (E.assembled_crossings_finite v hvinj hv hdet)] rfl rw [hcount] exact h.trans C.chordCrossings_ncard_le end PolygonalExterior end Paper170Geometry end end section /-! Appendix A's actual polygonal normalization, with full admissibility and point-count control. -/ noncomputable section open Zarankiewicz variable {Vertex Edge : Type} {graph : Paper170.Graph Vertex Edge} namespace Paper170Geometry namespace PolygonalExterior variable {D : FiniteIntersectionDrawing graph} {C : DrawingPassages D} theorem middlePath_hasFiniteAffineCover (E : PolygonalExterior C) (e : Edge) : HasFiniteAffineCover (E.middlePath e) := alternatingPath_hasFiniteAffineCover _ _ _ _ (fun i => (E.chain (C.orderedArc e i)).hasFiniteAffineCover) (fun _ => hasFiniteAffineCover_segment _ _) _ theorem assembledEdge_hasFiniteAffineCover (E : PolygonalExterior C) (v : Vertex → Plane) (e : Edge) : HasFiniteAffineCover (E.assembledEdge v e) := by apply HasFiniteAffineCover.trans · apply HasFiniteAffineCover.trans (hasFiniteAffineCover_segment _ _) exact E.middlePath_hasFiniteAffineCover e · simp only [endSpoke,Path.segment_symm] exact hasFiniteAffineCover_segment _ _ end PolygonalExterior /-- Finite contacts and no triples suffice to construct genuinely proper crossings. -/ theorem finite_intersection_normalization [Fintype Vertex] [Fintype Edge] (D : FiniteIntersectionDrawing graph) : ∃ D' : Paper170.AdmissibleDrawing graph, (∀ e, HasFiniteAffineCover (D'.edge e)) ∧ Paper170.crossingCount D' ≤ finiteCrossingCount D := by obtain ⟨C⟩ := nonempty_drawingPassages D obtain ⟨E⟩ := nonempty_polygonalExterior C obtain ⟨v,hvinj,hv,hne,hdet⟩ := C.exists_drawing_vertex_placement exact ⟨E.assembledAdmissible v hvinj hv hdet,E.assembledEdge_hasFiniteAffineCover v, E.assembled_crossingCount_le v hvinj hv hdet⟩ /-- An arbitrary admissible continuous drawing admits an actual admissible polygonal drawing with no more spatial crossing points. Vertices and routes are allowed to move. No one-crossing-per-pair or adjacency condition is assumed. -/ theorem polygonal_normalization [Fintype Vertex] [Fintype Edge] (D : Paper170.AdmissibleDrawing graph) : ∃ D' : Paper170.AdmissibleDrawing graph, (∀ e, HasFiniteAffineCover (D'.edge e)) ∧ Paper170.crossingCount D' ≤ Paper170.crossingCount D := by obtain ⟨C⟩ := nonempty_drawingPassages D.toFiniteIntersectionDrawing obtain ⟨E⟩ := nonempty_polygonalExterior C obtain ⟨v,hvinj,hv,hne,hdet⟩ := C.exists_drawing_vertex_placement exact ⟨E.assembledAdmissible v hvinj hv hdet,E.assembledEdge_hasFiniteAffineCover v, E.assembled_crossingCount_le v hvinj hv hdet⟩ end Paper170Geometry end end section /-! At equal total count, reassembly retains every original crossing and its incident pair. -/ noncomputable section open Set namespace Paper170Geometry open Zarankiewicz variable {Vertex Edge : Type} {graph : Paper170.Graph Vertex Edge} namespace DrawingPassages variable {D : FiniteIntersectionDrawing graph} theorem chordCrossingOrigin_eq_innerMark (C : DrawingPassages D) {y : Plane} (hy : y ∈ C.chordCrossings) (p : C.InnerIndex) (hp : y ∈ Set.range (C.crossingChord p)) : C.chordCrossingOrigin y = (C.innerMark p).val := by unfold chordCrossingOrigin rw [dite_eq_left hy] obtain ⟨r,s,hrs,hr,hs,hyr,hys⟩ := (C.chord_crossing_original_mark hy).choose_spec.2 exact congrArg Subtype.val ((C.chord_meeting_marks_eq p r hp hyr).trans hr).symm end DrawingPassages namespace PolygonalExterior variable {D : FiniteIntersectionDrawing graph} {C : DrawingPassages D} theorem assembled_origin_mem_pair (E : PolygonalExterior C) (v : Vertex → Plane) (hvinj : Function.Injective v) (hv : ∀ j, squaredLength (v j-D.vertex j) < C.radius^2) (hdet : ∀ j (p q : C.PortsAt (C.vertexMark j)), p ≠ q → det2 (C.portPoint p.val-v j) (C.portPoint q.val-v j) ≠ 0) (e f : Edge) (hef : e ≠ f) (y : Plane) (he : y ∈ Paper170.edgeInterior (E.assembledDrawing v hvinj hv) e) (hf : y ∈ Paper170.edgeInterior (E.assembledDrawing v hvinj hv) f) : C.chordCrossingOrigin y ∈ Paper170.edgeInterior D.toContinuousDrawing e ∧ C.chordCrossingOrigin y ∈ Paper170.edgeInterior D.toContinuousDrawing f := by have hy := E.assembled_crossings_subset v hvinj hv hdet ⟨e,f,hef,he,hf⟩ obtain ⟨s,hs,hys⟩ := he obtain ⟨t,ht,hyt⟩ := hf obtain ⟨p,q,hp,hq,hyp,hyq⟩ := E.assembled_meeting_chords v hv hdet e f hef y (fun j heq => E.assembledEdge_interior_avoids_vertices v hv e s hs j (hys.trans heq)) ⟨s,hys⟩ ⟨t,hyt⟩ constructor · rw [C.chordCrossingOrigin_eq_innerMark hy p hyp, ← hp] exact ⟨C.node p.1 p.2.val,C.inner_parameter_interior p,rfl⟩ · rw [C.chordCrossingOrigin_eq_innerMark hy q hyq, ← hq] exact ⟨C.node q.1 q.2.val,C.inner_parameter_interior q,rfl⟩ theorem assembled_origin_surj_of_count_eq (E : PolygonalExterior C) (v : Vertex → Plane) (hvinj : Function.Injective v) (hv : ∀ j, squaredLength (v j-D.vertex j) < C.radius^2) (hdet : ∀ j (p q : C.PortsAt (C.vertexMark j)), p ≠ q → det2 (C.portPoint p.val-v j) (C.portPoint q.val-v j) ≠ 0) (hcount : Paper170.crossingCount (E.assembledAdmissible v hvinj hv hdet) = finiteCrossingCount D) : Set.SurjOn C.chordCrossingOrigin (Paper170.crossingPoints (E.assembledDrawing v hvinj hv)) (Paper170.crossingPoints D.toContinuousDrawing) := by have hsub := E.assembled_crossings_subset v hvinj hv hdet have hmap := C.chordCrossingOrigin_mapsTo.mono_left hsub have hinj := C.chordCrossingOrigin_injOn.mono hsub have hsize : (Paper170.crossingPoints D.toContinuousDrawing).ncard ≤ (C.chordCrossingOrigin '' Paper170.crossingPoints (E.assembledDrawing v hvinj hv)).ncard := by rw [hinj.ncard_image, ← finiteCrossingCount_eq_ncard] rw [Set.ncard_eq_toFinset_card _ (E.assembled_crossings_finite v hvinj hv hdet)] exact hcount.ge have heq := Set.eq_of_subset_of_ncard_le hmap.image_subset hsize D.crossings_finite intro x hx rw [← heq] at hx exact hx theorem assembled_pair_retained_of_count_eq {D₀ : Paper170.AdmissibleDrawing graph} {C₀ : DrawingPassages D₀.toFiniteIntersectionDrawing} (E : PolygonalExterior C₀) (v : Vertex → Plane) (hvinj : Function.Injective v) (hv : ∀ j, squaredLength (v j-D₀.vertex j) < C₀.radius^2) (hdet : ∀ j (p q : C₀.PortsAt (C₀.vertexMark j)), p ≠ q → det2 (C₀.portPoint p.val-v j) (C₀.portPoint q.val-v j) ≠ 0) (hcount : Paper170.crossingCount (E.assembledAdmissible v hvinj hv hdet) = Paper170.crossingCount D₀) (e f : Edge) (hef : e ≠ f) (x : Plane) (hxe : x ∈ Paper170.edgeInterior D₀.toContinuousDrawing e) (hxf : x ∈ Paper170.edgeInterior D₀.toContinuousDrawing f) : ∃ y, y ∈ Paper170.edgeInterior (E.assembledDrawing v hvinj hv) e ∧ y ∈ Paper170.edgeInterior (E.assembledDrawing v hvinj hv) f := by obtain ⟨y,hy,hxy⟩ := E.assembled_origin_surj_of_count_eq v hvinj hv hdet hcount (show x ∈ Paper170.crossingPoints D₀.toContinuousDrawing from ⟨e,f,hef,hxe,hxf⟩) obtain ⟨a,b,hab,hya,hyb⟩ := hy have hold := E.assembled_origin_mem_pair v hvinj hv hdet a b hab y hya hyb rw [hxy] at hold have ha := (crossing_incident_iff D₀ x e f hef hxe hxf a).mp hold.1 have hb := (crossing_incident_iff D₀ x e f hef hxe hxf b).mp hold.2 rcases ha with rfl | rfl <;> rcases hb with rfl | rfl · exact False.elim (hab rfl) · exact ⟨y,hya,hyb⟩ · exact ⟨y,hyb,hya⟩ · exact False.elim (hab rfl) end PolygonalExterior end Paper170Geometry end end section /-! Subdivide actual polygonal drawings at all marks and any extra finite set of spatial points. -/ noncomputable section open Zarankiewicz variable {Vertex Edge : Type} {graph : Paper170.Graph Vertex Edge} namespace Paper170Geometry theorem exists_drawing_subdivision_at [Fintype Vertex] (D : Paper170.AdmissibleDrawing graph) (hpoly : ∀ e, HasFiniteAffineCover (D.edge e)) (S : Set Plane) (hS : S.Finite) : ∃ P : ∀ e, PolygonalParametrization (D.edge e), (∀ e t, D.edge e t ∈ drawingMarks D.toFiniteIntersectionDrawing → t ∈ Set.range (P e).knot) ∧ (∀ e t, D.edge e t ∈ S → t ∈ Set.range (P e).knot) := by classical have hfinite (e : Edge) : ((D.edge e) ⁻¹' (drawingMarks D.toFiniteIntersectionDrawing ∪ S)).Finite := ((drawingMarks_finite D.toFiniteIntersectionDrawing).union hS).preimage (D.edge_injective e).injOn have hex (e : Edge) := (hpoly e).refine (hfinite e).toFinset choose P hP using hex refine ⟨P,?_,?_⟩ · intro e t ht exact hP e (by simpa using Or.inl ht) · intro e t ht exact hP e (by simpa using Or.inr ht) namespace PolygonalExterior variable {D : Paper170.AdmissibleDrawing graph} {C : DrawingPassages D.toFiniteIntersectionDrawing} theorem exists_assembled_port_subdivision [Fintype Vertex] [Fintype Edge] (E : PolygonalExterior C) (v : Vertex → Plane) (hvinj : Function.Injective v) (hv : ∀ j, squaredLength (v j-D.vertex j) < C.radius^2) (hdet : ∀ j (p q : C.PortsAt (C.vertexMark j)), p ≠ q → det2 (C.portPoint p.val-v j) (C.portPoint q.val-v j) ≠ 0) : ∃ P : ∀ e, PolygonalParametrization ((E.assembledAdmissible v hvinj hv hdet).edge e), (∀ e t, E.assembledEdge v e t ∈ drawingMarks (E.assembledAdmissible v hvinj hv hdet).toFiniteIntersectionDrawing → t ∈ Set.range (P e).knot) ∧ (∀ e t, E.assembledEdge v e t ∈ Set.range C.portPoint → t ∈ Set.range (P e).knot) := exists_drawing_subdivision_at (E.assembledAdmissible v hvinj hv hdet) (E.assembledEdge_hasFiniteAffineCover v) (Set.range C.portPoint) (Set.finite_range _) end PolygonalExterior end Paper170Geometry end end end OAI