Timeline for Extension of the Peano Axioms?
Current License: CC BY-SA 3.0
5 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 9, 2020 at 19:04 | comment | added | Noah Schweber | @FrançoisG.Dorais I just now caught that ... excellent! | |
| Oct 17, 2011 at 3:30 | comment | added | François G. Dorais | Yes, and a simple compactness trick will also do it. In fact, it seems that it is hard not to prove that there are nonstandard models! | |
| Oct 17, 2011 at 2:57 | comment | added | Terry Tao | Alternatively, one can use Los's theorem instead of Lowenheim-Skolem: the ultrapower ${}^* {\bf N}$ of ${\bf N}$ obeys all the first order sentences that the natural numbers do, but is clearly a non-isomorphic model of arithmetic. | |
| Oct 17, 2011 at 1:49 | vote | accept | Lawrence Wickert | ||
| Oct 17, 2011 at 1:17 | history | answered | François G. Dorais | CC BY-SA 3.0 |