[FOM] cofinite quantifier

[praatika@mappi.helsinki.fi]

Thomas Forster <T.Forster at dpmms.cam.ac.uk> wrote:

> How undecidable is the theory of natural numbers with 
> the cofinite quantifier?  Does anyone know about this?


The following seems to be at least related:

{x : W_x is co-finite} is Sigma_3 -complete.

(ref.: H. Rogers: Theory of Recursive Functions and Effective 
Computability, p. 328.)

Best

Panu


Panu Raatikainen

PhD., Docent in Theoretical Philosophy
Fellow, Helsinki Collegium for Advanced Studies
University of Helsinki
 
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