@@ -828,15 +828,13 @@ lemma square_subset_above (h : (C ∩ level n).Finite) :
828828 -- If `(C ∩ level n)` is empty, trivially we are done.
829829 obtain h | hne := (C ∩ level n).eq_empty_or_nonempty
830830 · simp [h]
831-
832831 -- Otherwise take a maximal pair `(a, b)` so that any `(c, d, n)` in `C` satisfies
833832 -- `(c, d, n) ≤ (a, b, n)`.
834833 obtain ⟨a, b, hab⟩ : ∃ a b, ∀ c d, h(c, d, n) ∈ C → c ≤ a ∧ d ≤ b := by
835834 obtain ⟨⟨a, b⟩, hab⟩ := (h.image (fun t ↦ ((ofHollom t).1 , (ofHollom t).2 .1 ))).bddAbove
836835 use a, b
837836 intro c d hcd
838837 simpa using hab ⟨h(_, _, _), ⟨hcd, by simp⟩, rfl⟩
839-
840838 -- With this pair, we can use the "base" of the square as `max a b + 1`.
841839 rw [eventually_atTop]
842840 refine ⟨max a b + 1 , ?_⟩
@@ -846,7 +844,6 @@ lemma square_subset_above (h : (C ∩ level n).Finite) :
846844 Set.mem_setOf_eq, forall_exists_index, EmbeddingLike.apply_eq_iff_eq, Prod.mk.injEq,
847845 toHollom_le_toHollom_iff_fixed_right, Set.mem_diff, and_true, ← max_add_add_right,
848846 Hollom.ext_iff]
849-
850847 -- After simplifying, direct calculations show the subset relation as required.
851848 rintro k hak hbk _ _ _ f g hkf hkg rfl rfl rfl
852849 constructor
@@ -947,15 +944,13 @@ We will later show the same assuming `C ∩ level (n + 1)` is infinite.
947944lemma square_subset_S_case_1 (h : (C ∩ level n).Finite) (h' : (C ∩ level (n + 1 )).Finite) :
948945 ∀ᶠ a in atTop, embed n '' Set.Ici (a, a) ⊆ S n C \ (C ∩ level n) := by
949946 rw [S, if_pos h']
950-
951947 -- Take a maximal pair `(b, c)` so that any `(d, e, n)` in `C` satisfies
952948 -- `(d, e, n) ≤ (b, c, n)`.
953949 obtain ⟨b, c, hab⟩ : ∃ b c, ∀ d e, h(d, e, n + 1 ) ∈ C → (d, e) ≤ (b, c) := by
954950 obtain ⟨⟨b, c⟩, hbc⟩ := (h'.image (fun t ↦ ((ofHollom t).1 , (ofHollom t).2 .1 ))).bddAbove
955951 use b, c
956952 intro d e hde
957953 simpa using hbc ⟨h(_, _, _), ⟨hde, by simp⟩, rfl⟩
958-
959954 -- Using `a ≥ max b c`, we have that all elements of `{(x, y, n) | x ≥ a ∧ y ≥ a}` are comparable
960955 -- to all elements of `C ∩ level (n + 1)`.
961956 have : ∀ᶠ a in atTop, embed n '' .Ici (a, a) ⊆ {x | ∀ y ∈ C ∩ level (n + 1 ), x ≤ y ∨ y ≤ x} := by
@@ -971,7 +966,6 @@ lemma square_subset_S_case_1 (h : (C ∩ level n).Finite) (h' : (C ∩ level (n
971966 have := hab _ _ hgh
972967 simp only [Prod.mk_le_mk] at this ⊢
973968 omega
974-
975969 -- Combined with the fact that sufficiently large `a` have
976970 -- `{(x, y, n) | x ≥ a ∧ y ≥ a} ⊆ R \ (C ∩ level n)`, we can easily finish.
977971 filter_upwards [square_subset_R h, this] with a h₁ h₂
@@ -1041,7 +1035,6 @@ theorem not_S_hits_next (f : SpinalMap C) (hC : IsChain (· ≤ ·) C)
10411035 simp only [level_eq, Set.mem_setOf_eq] at this
10421036 intro h
10431037 simp [level_eq, h, this] at hy
1044-
10451038 -- So suppose it is infinite
10461039 case inr h =>
10471040 -- Write `(x, y, n)` for our given point, and set `(a, b, n + 1) := f(x, y, n)`
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