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arXiv · 1912.12962

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

Vladimir Kanovei·Vassily Lyubetsky
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Abstract

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.

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Vladimir Kanovei, Vassily Lyubetsky. 2019-12-30. Indiscernible pairs of countable sets of reals at a given projective level. https://arxiv.org/abs/1912.12962

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