English
The x-variation of the right-hand expression is measurable in x for fixed a.
Русский
Для фиксированного a выражение слева/права измеримо по x.
LaTeX
$$$\text{Measurable}\left( x \mapsto \text{Real.toNNReal}(rnDerivAux(\kappa, (\kappa+\eta)) a x) - \text{Real.toNNReal}(1 - rnDerivAux(\kappa, (\kappa+\eta)) a x) \cdot rnDeriv(\kappa, \eta) a x \right)$$$
Lean4
theorem measurable_singularPart_fun_right (κ η : Kernel α γ) (a : α) :
Measurable
(fun x : γ ↦
Real.toNNReal (rnDerivAux κ (κ + η) a x) - Real.toNNReal (1 - rnDerivAux κ (κ + η) a x) * rnDeriv κ η a x) :=
by
change
Measurable
((Function.uncurry fun a b ↦
ENNReal.ofReal (rnDerivAux κ (κ + η) a b) - ENNReal.ofReal (1 - rnDerivAux κ (κ + η) a b) * rnDeriv κ η a b) ∘
(fun b ↦ (a, b)))
exact (measurable_singularPart_fun κ η).comp measurable_prodMk_left