Zulip Chat Archive
Stream: Is there code for X?
Topic: Volume nonzero of nonempty interior
Alex Kontorovich (Aug 18 2023 at 22:37):
Do we have (perhaps under some conditions) the fact that a MeasurableSet
with Nonempty
interior
has positive measure?
import Mathlib.MeasureTheory.Constructions.BorelSpace.Basic
open MeasureTheory Set
example {α : Type _} [TopologicalSpace α] [MeasureSpace α] [BorelSpace α] (s : Set α)
(hs : Nonempty (interior s)) (s_meas : MeasurableSet s) : 0 < volume s := by
sorry -- exact? fails
Anatole Dedecker (Aug 18 2023 at 22:49):
Well it's true (almost) by definition if you have docs#MeasureTheory.Measure.IsOpenPosMeasure
Alex Kontorovich (Aug 18 2023 at 23:01):
Perfect, exactly what I was looking for, thanks!
Last updated: Dec 20 2023 at 11:08 UTC