Axiom Of Choice

We have the following indirect implication of form equivalence classes:

68 \(\Rightarrow\) 127 given by the following sequence of implications, with a reference to its direct proof:

Implication	Reference
68 \(\Rightarrow\) 62	Subgroups of a free group and the axiom of choice, Howard, P. 1985, J. Symbolic Logic
62 \(\Rightarrow\) 61	clear
61 \(\Rightarrow\) 45-n	clear
45-n \(\Rightarrow\) 64	Classes of Dedekind finite cardinals, Truss, J. K. 1974a, Fund. Math.
64 \(\Rightarrow\) 127	Amorphe Potenzen kompakter Raume, Brunner, N. 1984b, Arch. Math. Logik Grundlagenforschung

Here are the links and statements of the form equivalence classes referenced above:

Howard-Rubin Number	Statement
68:	Nielsen-Schreier Theorem: Every subgroup of a free group is free. Jech [1973b], p 12.
62:	\(C(\infty,< \aleph_{0})\): Every set of non-empty finite sets has a choice function.
61:	\((\forall n\in\omega, n\ge 2\))\((C(\infty,n))\): For each \(n\in\omega\), \(n\ge 2\), every set of \(n\) element sets has a choice function.
45-n:	If \(n\in\omega-\{0,1\}\), \(C(\infty,n)\): Every set of \(n\)-element sets has a choice function.
64:	\(E(I,Ia)\) There are no amorphous sets. (Equivalently, every infinite set is the union of two disjoint infinite sets.)
127:	An amorphous power of a compact \(T_2\) space, which as a set is well orderable, is well orderable.

Comment:

Back