OAI/Analysis/KadisonSimilarity/Representation/CountableLpSubsequence.lean
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A common almost-everywhere subsequence for countably many L² columns. The fast diagonal choice uses summable errors, so the same sequence works for every column.
- theorem
OAI.KadisonSimilarity.exists_countable_L2_ae_subsequenceline 21Source documentation
Countably many L² limits have one choice of indices with simultaneous pointwise convergence almost everywhere.
theorem exists_countable_L2_ae_subsequence (f : ℕ → ℕ → Lp H 2 μ) (g : ℕ → Lp H 2 μ) (hf : ∀ j, Tendsto (fun n => f n j) atTop (𝓝 (g j))) : ∃ k : ℕ → ℕ, (∀ n, n ≤ k n) ∧ ∀ᵐ a ∂μ, ∀ j, Tendsto (fun n => f (k n) j a) atTop (𝓝 (g j a)) := by …