English
If X equals Y almost everywhere with respect to ℙ, then HasPDF X ℙ μ implies HasPDF Y ℙ μ.
Русский
Если X и Y равны почти всюду по отношению к ℙ, то HasPDF X ℙ μ влечёт HasPDF Y ℙ μ.
LaTeX
$$$(X =^{\\mathrm{a.e.}}_{\\ℙ} Y) \\Rightarrow (HasPDF X \\ℙ μ \\Rightarrow HasPDF Y \\ℙ μ)$$$
Lean4
theorem congr (hXY : X =ᵐ[ℙ] Y) [hX : HasPDF X ℙ μ] : HasPDF Y ℙ μ :=
⟨(HasPDF.aemeasurable X ℙ μ).congr hXY, ℙ.map_congr hXY ▸ hX.haveLebesgueDecomposition,
ℙ.map_congr hXY ▸ hX.absolutelyContinuous⟩