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arXiv:1912.12962 [math.LO]AbstractReferencesReviewsResources

Indiscernible pairs of countable sets of reals at a given projective level

Vladimir Kanovei, Vassily Lyubetsky

Published 2019-12-30Version 1

Using an invariant modification of Jensen's "minimal $\varPi^1_2$ singleton" forcing, we define a model of ZFC, in which, for a given $n\ge2$, there exists a lightface $\varPi^1_n$ unordered pair of non-OD (hence, OD-indiscernible) countable sets of reals, but there is no $\varSigma^1_n$ unordered pairs of this kind.

Categories: math.LO
Subjects: 03E15, 03E35
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