How statement and proof provenance work
The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.
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These labels describe origin, not correctness: citations and verification chips remain separate evidence.
Stone ultrafilter space and its clopen basis
Definition
For a Boolean algebra , let be its set of ultrafilters and put . Give it the topology consisting of all unions of such sets. The filter tests give
These equations ensure that the proposed unions form a topology: the empty union and whole space occur, arbitrary unions are unions of basic sets, and finite intersections distribute over such unions. The sets form a clopen basis. This definition does not assert compactness or the existence of ultrafilters.
A Stone space is a compact, Hausdorff space with a basis of clopen subsets. The empty space is allowed. For any space , write for its clopen subsets, with union, intersection, complement relative to , and bounds ; finite unions and intersections of clopens and their complements are clopen, so these form a Boolean algebra. The trivial Boolean algebra has no ultrafilters and thus gives the empty space.
Depends on
- Generated filters and the complementary-pair tests
- Topology on a set, open and closed sets, clopen sets, the closed-set axiomatisation, and the coarser/finer comparison
- Hausdorff space: distinct points have disjoint open neighbourhoods; every metrizable space is Hausdorff and the indiscrete topology on two points is not
- Open cover, subcover, and compact topological space; a compact subset is a subspace that is compact in its own right
Used by
- A finite quotient and its dual inclusion Example
- The Stone space of a finite powerset algebra Example
- A Stone space is recovered from its clopens Theorem
- Compact Hausdorff Tychonoff is equivalent to BPI Theorem
- Extreme amenability yields BPI in finite-support permutation models Theorem
- Stone clopen representation under BPI Theorem
Dependency tree · two levels
15 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.
Sources
- Tressl, Stone Duality for Boolean Algebras, 3.1.1–3.1.3, p. 10 (standard reference, not scraped)