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A computability theoretic equivalent to Vaught's conjecture
We prove that, for every theory which is given by an sentence, has less than many countable
models if and only if we have that, for every on a cone of
Turing degrees, every -hyperarithmetic model of has an -computable
copy. We also find a concrete description, relative to some oracle, of the
Turing-degree spectra of all the models of a counterexample to Vaught's
conjecture
Relation algebras from cylindric algebras, I
Accepted versio
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