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Many theorems provable using choice are of an elegant general character: the cardinalities of any two sets are comparable, every nontrivial ring with unity has a maximal ideal, every vector space has a basis, every connected graph has a spanning tree, and every product of compact spaces is compact, among many others. Frequently, the axiom of ...
For infinite dimensional manifolds, this is sometimes taken to be the definition of an immersion. [4] An injectively immersed submanifold that is not an embedding. If M is compact, an injective immersion is an embedding, but if M is not compact then injective immersions need not be embeddings; compare to continuous bijections versus homeomorphisms.
The mathematical statements discussed below are provably independent of ZFC (the canonical axiomatic set theory of contemporary mathematics, consisting of the Zermelo–Fraenkel axioms plus the axiom of choice), assuming that ZFC is consistent. A statement is independent of ZFC (sometimes phrased "undecidable in ZFC") if it can neither be ...
Using the axiom of choice, one can show that for any family S of sets | ⋃S | ≤ | S | × sup { |s| : s ∈ S} (A). [5] Moreover, by Tarski's theorem on choice, another equivalent of the axiom of choice, | X | n = | X | for all finite n (B). Let X be an infinite set and let F denote the set of all finite subsets of X. There is a natural ...
In mathematics, Tarski's theorem, proved by Alfred Tarski , states that in ZF the theorem "For every infinite set , there is a bijective map between the sets and " implies the axiom of choice. The opposite direction was already known, thus the theorem and axiom of choice are equivalent.
The theorem is a foregone conclusion over classical logic, where law of the excluded middle is assumed. The proof below is therefore given using the means of a constructive set theory. It is evident from the proof how the theorem relies on the axiom of pairing as well as an axiom of separation, of which there are
This image of the open interval (with boundary points identified with the arrow marked ends) is an immersed submanifold. An immersed submanifold of a manifold is the image of an immersion map :; in general this image will not be a submanifold as a subset, and an immersion map need not even be injective (one-to-one) – it can have self-intersections.
Soundness theorem; Gödel's completeness theorem. Original proof of Gödel's completeness theorem; Compactness theorem; Löwenheim–Skolem theorem. Skolem's paradox; Gödel's incompleteness theorems; Structure (mathematical logic) Interpretation (logic) Substructure (mathematics) Elementary substructure. Skolem hull; Non-standard model; Atomic ...