
Re: Size of ordinal for ordinal definable real
Posted:
Dec 29, 2013 5:01 AM


Peter Percival <peterxpercival@hotmail.com> writes:
> Suppose phi(x,alpha) is a formula of ZFC (or your favourite set > theory) such that for all real x there is an ordinal alpha such that > phi(x,alpha) holds. (I.e. x is an ordinal definable real.) How big > does alpha need to be?
In the constructible universe, a new real (set of naturals) appears at each countable level.
 Aatu Koskensilta (aatu.koskensilta@uta.fi)
"Wovon man nicht sprechen kann, darüber muss man schweigen"  Ludwig Wittgenstein, Tractatus LogicoPhilosophicus

