[FOM] Church-Kleene or Feferman-Schutte

Andreas Weiermann Andreas.Weiermann at UGent.be
Tue May 14 11:48:27 EDT 2013


Dear Sandro,

- when I understood the question correctly -  the Feferman-Schutte ordinal
like every proof-theoretic ordinal (which by definition is a recursive 
ordinal)
comes before the first non recursive ordinal \omega_1^CK.

But maybe I misunderstood something.

Best,
Andreas

On 14/05/13 01:03, Sandro Skansi wrote:
> I was looking through my books and journals for to compile a list of 
> ordinals used in proof theory, but I did not seem to find anything 
> that could really help me make a diagram, except for Pohlers 1996 BSL 
> article. There I found almost everything, but I was not able to find 
> this, so I am asking it here on the FOM list:
>
> In terms of ordinals, starting from \omega, which one comes first, the 
> Church-Kleene ordinal (\omega_1^CK) or the Feferman-Schutte ordinal 
> (\Gamma_0)?
>
> Best regards,
>
> Sandro Skansi
>
>
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