English
For any setoid s on a Polish space X, the quotient space X/ s carries a Borel space structure: BorelSpace (Quotient s).
Русский
Для произвольной эквивалентности на полическом пространстве X, фактор-пространство X/ s обладает борелевой структурой: BorelSpace (Quotient s).
LaTeX
$$BorelSpace (Quotient s)$$
Lean4
instance borelSpace {X : Type*} [TopologicalSpace X] [PolishSpace X] [MeasurableSpace X] [BorelSpace X] {s : Setoid X}
[T0Space (Quotient s)] [SecondCountableTopology (Quotient s)] : BorelSpace (Quotient s) :=
⟨continuous_quotient_mk'.map_eq_borel Quotient.mk'_surjective⟩