English
For a finite measure μ and HaveLebesgueDecomposition with ν, the integrability of a smoothed RN-derivative weighted by a vector-valued function f is equivalent to the integrability of f with respect to μ.
Русский
Для μ конечной меры и разложенияHaveLebesgueDecomposition, интегрируемость модуля плотности умноженной на f равна интегрируемости f по μ.
LaTeX
$$$$ \text{Integrable}\left( x \mapsto (μ.rnDeriv ν x).toReal \cdot f(x) \, , ν \right) \iff \text{Integrable}(f, μ) $$$$
Lean4
/-- The dirac measure. -/
def dirac (a : α) : Measure α :=
(OuterMeasure.dirac a).toMeasure (by simp)