English
If f is locally integrable and g is a.e. bounded in norm by f, then g is locally integrable.
Русский
Если f локально интегрируема и почти везде по норме ограничена сверху на g на f, то g локально интегрируема.
LaTeX
$$$\\operatorname{LocallyIntegrable} f\\mu \\Rightarrow \\forall g,\\ \\text{AEStronglyMeasurable } g\\mu \\wedge (\\forall^{\\!a.e.} x, \\|g(x)\\| \\le \\|f(x)\\|) \\Rightarrow \\operatorname{LocallyIntegrable} g\\mu$$$
Lean4
theorem mono_enorm (hf : LocallyIntegrable f μ) {g : X → ε'} (hg : AEStronglyMeasurable g μ)
(h : ∀ᵐ x ∂μ, ‖g x‖ₑ ≤ ‖f x‖ₑ) : LocallyIntegrable g μ :=
by
rw [← locallyIntegrableOn_univ] at hf ⊢
exact hf.mono_enorm hg h