# Borel Sets and Hyperdegrees

@article{Friedman1973BorelSA, title={Borel Sets and Hyperdegrees}, author={H. Friedman}, journal={J. Symb. Log.}, year={1973}, volume={38}, pages={405-409} }

This paper is concerned with the hyderdegrees of elements of uncountable Borel subsets of ω ω . The Borel subsets of ω ω are the so-called Δ 1 1 subsets of ω ω , which are the subsets of ω ω that are Δ 1 1 in some parameter f : ω → ω . The results of this paper were inspired by two earlier results about the hyperdegrees of elements of Σ 1 1 subsets of ω ω . The first is known as the Gandy basis theorem, and asserts that the collection of functions of strictly lower hyperdegree than the… Expand

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