Timeline for Idempotent ultrafilters and the Rudin-Keisler ordering
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
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| Aug 4, 2013 at 17:28 | history | edited | Noah Schweber | CC BY-SA 3.0 |
added 39 characters in body
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| Aug 4, 2013 at 1:26 | comment | added | Peter Krautzberger | Todd, see my comment to Andreas's answer -- given any two ultrafilters $p,q$ you'll find an idempotent u with $f(u)=p, g(u)=q$. | |
| Aug 3, 2013 at 22:57 | vote | accept | Noah Schweber | ||
| Aug 3, 2013 at 17:42 | answer | added | Andreas Blass | timeline score: 12 | |
| Aug 3, 2013 at 15:36 | comment | added | Todd Eisworth | Random Conjecture: Suppose U is idempotent, let $f$ ($g$) be the map sending n to the position of the rightmost (leftmost) 1 in its binary expansion. Then $f(U)$ and $g(U)$ are not RK-equivalent to each other or to $U$. | |
| Aug 3, 2013 at 15:34 | comment | added | Todd Eisworth | The last section of Andreas's "Ultrafilters: Where Dynamics = Algebra = Combinatorics" has some remarks on the relationship between idempotents, Ramsey ultrafilters, and P-points. | |
| Aug 3, 2013 at 5:52 | history | asked | Noah Schweber | CC BY-SA 3.0 |