Abstract:
Studying computable representations of projective planes, for the classes $K$ of pappian, desarguesian, and all projective planes, we prove that $K^c/_\simeq$ admits no hyperarithmetical Friedberg enumeration and admits a Friedberg $\Delta^0_{\alpha+3}$-computable enumeration up to a $\Delta^0_\alpha$-computable isomorphism.
Keywords:pappian projective plane, desarguesian projective plane, freely generated projective plane, computable model, computable class of models, computable isomorphism.