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coudy
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continuity of equivalence relations

A function φ : X → Y between two topological spaces is continuous if and only if φ(adh A) ⊂ adh (φ A) for all A ⊂ X.

This property can be extended to equivalence relations as follows. Given an equivalence relation R on X and A ⊂ X, we denote by R(A) the set of points equivalent to points in A. We can look at the property of R given by

$$R\Bigl(\overline{A}\Bigr) \subset \overline{R(A)} \ \ for\ \ all\ \ A ⊂ X.$$

Is there a name for that property? Is it studied somewhere? Can it be formulated in term of the continuity of some function associated To R?

I encountered this property while studying the equivalence relation associated to a foliation ("being on the same leaf").

coudy
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