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arXiv · 2105.06403

Hjorth's reflection argument

Grigor Sargsyan
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Abstract

Hjorth, assuming ${\sf{AD+ZF+DC}}$, showed that there is no sequence of length $\omega_2$ consisting of distinct $\Sigma^1_2$-sets. We show that the same theory implies that for $n\geq 0$, there is no sequence of length $\delta^1_{2n+2}$ consisting of distinct $\Sigma^1_{2n+2}$ sets. The theorem settles Question 30.21 of Kanamori, which was also conjectured by Kechris.

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Grigor Sargsyan. 2021-05-13. Hjorth's reflection argument. https://arxiv.org/abs/2105.06403

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