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M. H. Stone's representation theorem (Theorem)
Theorem 1   Given a Boolean algebra $B$ there exists a totally disconnected compact Hausdorff space $X$ such that $B$ is isomorphic to the Boolean algebra of clopen subsets of $X$ .
Proof. [Still very rough sketch of proof, slowly filling in details] Let the set $X$ be defined as follows: $$X=\left\{f\co B\to \{0,1\} \mid f \text{ is a homomorphism}\right\}$$ Alternatively, $X$ may be defined as the set of all ultrafilters of $B$ . (Recall that a subset of a Boolean algebra is the kernel of a homomorphism if and only if it is an ultrafilter.) We may endow $X$ with the subspace topology induced by the product topology on ${\{0,1\}}^B$ . Recall that a basis for this topology is given by the sets $O_{i} (x)$ where $i = 0,1$ and $x \in B$ . These sets are defined as follows: $$O_i (x) = \{ f \in X \mid f(x) = i \}$$

Let us note that $X$ is a closed subspace of ${\{0,1\}}^B$ . Suppose that $g \notin X$ . By definition, $g$ is not a homomorphism, so there must exist $x,y \in B$ such that $g (\sim (x \cup y)) \neq \sim (g(x) \cup g(y))$ . Then no element of the open set $O_{g(x)} (x) \cap O_{g(y)} (y) \cap O_{g (\sim (x \cup y))} (\sim (x \cup y))$ will be a homomorphism because, for every element $h$ of this set, $$h (\sim (x \cup y)) = g (\sim (x \cup y)) \neq \sim (g(x) \cup g(y)) = \sim (h(x) \cup h(y))$$ By Tychonoff's theorem, ${\{0,1\}}^B$ is compact. Hence, as a closed subset of a compact topological space, $X$ is compact.

Then $X$ is a totally disconnected Hausdorff space. Let $\mathrm{Cl}(X)$ denote the Boolean algebra of clopen subsets of $X$ , then the following map $$T\co B \to \mathrm{Cl}(X),\quad T(x)=\{f\in X\,|\, f(x)=1\}$$ is well defined (i.e. $T(x)$ is indeed a clopen set), and an isomorphism. $ \qedsymbol$




"M. H. Stone's representation theorem" is owned by rspuzio. [ full author list (2) | owner history (1) ]
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Other names:  Stone representation theorem, Stone's representation theorem
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Cross-references: well defined, map, closed subset, Tychonoff's theorem, open set, subspace, closed, topology, basis, product topology, induced, subspace topology, homomorphism, kernel, subset, ultrafilters, proof, clopen subsets, isomorphic, Hausdorff space, compact, totally disconnected, Boolean algebra
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This is version 14 of M. H. Stone's representation theorem, born on 2003-02-06, modified 2008-05-01.
Object id is 3983, canonical name is MHStonesRepresentationTheorem.
Accessed 5147 times total.

Classification:
AMS MSC03G05 (Mathematical logic and foundations :: Algebraic logic :: Boolean algebras)
 06E99 (Order, lattices, ordered algebraic structures :: Boolean algebras :: Miscellaneous)
 54D99 (General topology :: Fairly general properties :: Miscellaneous)

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