Let Ω be a set, and 𝒫(Ω) be the power setMathworldPlanetmath of Ω. A π-system (or pi-system) on Ω is a set 𝒫(Ω) such that

A,BAB. (1)

A π-system is closed under finite intersectionMathworldPlanetmath.

Title pi-system
Canonical name Pisystem
Date of creation 2013-03-22 12:21:23
Last modified on 2013-03-22 12:21:23
Owner drummond (72)
Last modified by drummond (72)
Numerical id 4
Author drummond (72)
Entry type Definition
Classification msc 03E20
Classification msc 28A60
Related topic DynkinSystem
Related topic SigmaAlgebra
Related topic DynkinsLemma