We have the following indirect implication of form equivalence classes:
| Implication | Reference |
|---|---|
| 344 \(\Rightarrow\) 62 | clear |
| 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 |
|---|---|
| 344: | If \((E_i)_{i\in I}\) is a family of non-empty sets, then there is a family \((U_i)_{i\in I}\) such that \(\forall i\in I\), \(U_i\) is an ultrafilter on \(E_i\). |
| 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. |
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