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LeanPool.CaffarelliKohnNirenberg.Leray.CompactnessWeakLower

Compactness Weak Lower #

Supporting estimates for the Navier–Stokes development.

theorem CKN.Leray.eLpNorm_le_of_weak_l2_bounded {α : Type u_1} {E : Type u_2} [MeasurableSpace α] [NormedAddCommGroup E] [InnerProductSpace ℝ E] {μ : MeasureTheory.Measure α} (f : ℕ → α → E) (g : ↥(MeasureTheory.Lp E 2 μ)) (hf : ∀ (k : ℕ), MeasureTheory.MemLp (f k) 2 μ) (hweak : ∀ (w : ↥(MeasureTheory.Lp E 2 μ)), Filter.Tendsto (fun (k : ℕ) => inner ℝ (MeasureTheory.MemLp.toLp (f k) ⋯) w) Filter.atTop (nhds (inner ℝ g w))) (B : ENNReal) (hB : B < ⊤) (hbound : ∀ (k : ℕ), MeasureTheory.eLpNorm (f k) 2 μ ≤ B) :
MeasureTheory.eLpNorm (fun (z : α) => ↑↑g z) 2 μ ≤ B

A finite uniform L² seminorm bound passes to a weak Hilbert-space limit with the same constant.