Commuting probabilities are closed
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Problem statement
Notes: The set of commuting probabilities of finite groups is closed.
Source: https://arxiv.org/abs/2201.09402
Informal solution: Neumann's theorem describes the structure of finite groups with bounded below commuting probability. Then pass to subsequences of groups with similar structure.
theorem commProb_closed : IsClosed ({p : ℝ | ∃ (G : Type) (hG : Group G), commProb G = p}) := ⊢ IsClosed {p | ∃ G hG, ↑(commProb G) = p}
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