arXiv · 1508.01547
We describe a proof-theoretic bound on $Sigma_{2}$-definable countable ordinals in Kripke-Platek set theory with $Pi_{1}$-Collection and the existence of $omega_{1}$.
Toshiyasu Arai. 2015-08-06. $omega_{1}$ under $Pi_{1}$-Collection. https://arxiv.org/abs/1508.01547
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