For every ergodic flow on a nonatomic probability space, there is a measurable set intersecting almost every orbit in a discrete set.
Ambrose-Kakutani Theorem
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Cite this as:
Weisstein, Eric W. "Ambrose-Kakutani Theorem." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Ambrose-KakutaniTheorem.html