[Merged by Bors] - feat(MetricSpace/Ultra): IsUltrametricDist and basic facts on open/closed sets in such spaces#14433
[Merged by Bors] - feat(MetricSpace/Ultra): IsUltrametricDist and basic facts on open/closed sets in such spaces#14433
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…osed in such spaces
PR summary 00154257b5Import changes for modified filesNo significant changes to the import graph Import changes for all files
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j-loreaux
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Thanks! I think there are some easy simplifications that can be made. I'll have another look when you think it's ready again.
Co-authored-by: Jireh Loreaux <loreaujy@gmail.com>
j-loreaux
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Sorry for missing the point of the trichotomy lemmas earlier. Here they are again with short proofs. You are welcome to add them back in.
lemma ball_subset_trichotomy :
ball x r ⊆ ball y s ∨ ball y s ⊆ ball x r ∨ Disjoint (ball x r) (ball y s) := by
wlog hrs : r ≤ s generalizing x y r s
· rw [disjoint_comm, ← or_assoc, or_comm (b := _ ⊆ _), or_assoc]
exact this y x s r (lt_of_not_le hrs).le
· refine Set.disjoint_or_nonempty_inter (ball x r) (ball y s) |>.symm.imp (fun h ↦ ?_) (Or.inr ·)
obtain ⟨hxz, hyz⟩ := (Set.mem_inter_iff _ _ _).mp h.some_mem
have hx := ball_subset_ball hrs (x := x)
rwa [ball_eq_of_mem hyz |>.trans (ball_eq_of_mem <| hx hxz).symm]
lemma closedBall_subset_trichotomy :
closedBall x r ⊆ closedBall y s ∨ closedBall y s ⊆ closedBall x r ∨
Disjoint (closedBall x r) (closedBall y s) := by
wlog hrs : r ≤ s generalizing x y r s
· rw [disjoint_comm, ← or_assoc, or_comm (b := _ ⊆ _), or_assoc]
exact this y x s r (lt_of_not_le hrs).le
· refine Set.disjoint_or_nonempty_inter (closedBall x r) (closedBall y s) |>.symm.imp
(fun h ↦ ?_) (Or.inr ·)
obtain ⟨hxz, hyz⟩ := (Set.mem_inter_iff _ _ _).mp h.some_mem
have hx := closedBall_subset_closedBall hrs (x := x)
rwa [closedBall_eq_of_mem hyz |>.trans (closedBall_eq_of_mem <| hx hxz).symm]Co-authored-by: Jireh Loreaux <loreaujy@gmail.com>
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up to potentially reordering lemmas to make things match better, I'm happy. If you want to reorder go for it, but it's not required. bors d+ |
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bors r+ |
…osed sets in such spaces (#14433) TODO in future PRs - add "all triangles are isosceles" in such normed spaces - totally disconnected space - give instances of this to Z_p, Q_p, etc Co-authored-by: Yakov Pechersky <pechersky@users.noreply.github.com>
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Pull request successfully merged into master. Build succeeded: |
TODO in future PRs