Timeline for A Question related to the Formula Hierarchy
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
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| Oct 30, 2014 at 14:39 | history | edited | François G. Dorais | CC BY-SA 3.0 |
added 84 characters in body
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| Oct 30, 2014 at 14:38 | vote | accept | Frode Alfson Bjørdal | ||
| Oct 30, 2014 at 14:21 | history | edited | François G. Dorais | CC BY-SA 3.0 |
and now the second case
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| Oct 30, 2014 at 13:30 | comment | added | Frode Alfson Bjørdal | (Of course, there is a qualification in that the argument presupposes the compactness of $2^\mathbb{N}$.) | |
| Oct 30, 2014 at 13:26 | comment | added | Frode Alfson Bjørdal | @François Somehow your statement must be further and appropriately qualified it seems to me. If not, the whole second order formula hierarchy of Second Order Arithmetic collapses for systems stronger than $WKL_0$, right? | |
| Oct 30, 2014 at 11:02 | comment | added | Emil Jeřábek | This is a very good point. Do I understand it correctly that if $\alpha$ is $\Pi^0_1$, a similar agument makes the formula $\Pi^1_1$ already in RCA_0? | |
| Oct 30, 2014 at 1:43 | history | answered | François G. Dorais | CC BY-SA 3.0 |