Hjorth's reflection argument
Fuente:
arXiv
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| Autore principale: | |
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| Natura: | Preprint |
| Pubblicazione: |
2021
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| Soggetti: | |
| Accesso online: | |
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| _version_ | 1866909531961819136 |
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| author | Sargsyan, Grigor |
| author_facet | Sargsyan, Grigor |
| contents | Hjorth, assuming ${\sf{AD+ZF+DC}}$, showed that there is no sequence of length $ω_2$ consisting of distinct $Σ^1_2$-sets. We show that the same theory implies that for $n\geq 0$, there is no sequence of length $δ^1_{2n+2}$ consisting of distinct $Σ^1_{2n+2}$ sets. The theorem settles Question 30.21 of Kanamori, which was also conjectured by Kechris. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2105_06403 |
| institution | arXiv |
| publishDate | 2021 |
| record_format | arxiv |
| spellingShingle | Hjorth's reflection argument Sargsyan, Grigor Logic Hjorth, assuming ${\sf{AD+ZF+DC}}$, showed that there is no sequence of length $ω_2$ consisting of distinct $Σ^1_2$-sets. We show that the same theory implies that for $n\geq 0$, there is no sequence of length $δ^1_{2n+2}$ consisting of distinct $Σ^1_{2n+2}$ sets. The theorem settles Question 30.21 of Kanamori, which was also conjectured by Kechris. |
| title | Hjorth's reflection argument |
| topic | Logic |
| url | https://arxiv.org/abs/2105.06403 |