Math 2.0

Order, lattices, ordered algebraic structures Constructions of ordered sets Example

Power set Boolean algebra

Example

Let XX be a set, and let 𝒫(X)\mathcal{P}(X) be the set of all subsets of XX. With A∧B=A∩BA \wedge B = A \cap B, A∨B=A∪BA \vee B = A \cup B, ¬A=X∖A\neg A = X \setminus A, 0=∅0 = \varnothing and 1=X1 = X, the set 𝒫(X)\mathcal{P}(X) is a Boolean algebra. Its order is inclusion ⊆\subseteq.

Remarks

If XX has nn elements, this Boolean algebra has 2n2^n elements. A field of sets on XX is a subset of 𝒫(X)\mathcal{P}(X) that contains ∅\varnothing and is closed under complement and binary union. It is a Boolean subalgebra. Every finite Boolean algebra is isomorphic to a power set Boolean algebra, by Stone's representation theorem for finite Boolean algebras.

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Further reading

  1. Web https://en.wikipedia.org/wiki/Field_of_sets, Definitions
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