We have the following indirect implication of form equivalence classes:
| Implication | Reference |
|---|---|
| 384 \(\Rightarrow\) 14 |
"Maximal filters, continuity and choice principles", Herrlich, H. 1997, Quaestiones Math. |
| 14 \(\Rightarrow\) 63 | clear |
| 63 \(\Rightarrow\) 70 | clear |
| 70 \(\Rightarrow\) 206 | clear |
| 206 \(\Rightarrow\) 223 | clear |
Here are the links and statements of the form equivalence classes referenced above:
| Howard-Rubin Number | Statement |
|---|---|
| 384: | Closed Filter Extendability for \(T_1\) Spaces: Every closed filter in a \(T_1\) topological space can be extended to a maximal closed filter. |
| 14: | BPI: Every Boolean algebra has a prime ideal. |
| 63: |
\(SPI\): Weak ultrafilter principle: Every infinite set has a non-trivial ultrafilter.
|
| 70: | There is a non-trivial ultrafilter on \(\omega\). Jech [1973b], prob 5.24. |
| 206: | The existence of a non-principal ultrafilter: There exists an infinite set \(X\) and a non-principal ultrafilter on \(X\). |
| 223: | There is an infinite set \(X\) and a non-principal measure on \(\cal P(X)\). |
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