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9 September 2023
RhubarbJayde
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+106
RhubarbJayde
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+50
RhubarbJayde
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+504
RhubarbJayde
Created page with "Ordinal definability is a concept which is key in certain aspects of inner model theory. We say a set \(x\) is ordinal-definable iff there is an ordinal \(\beta\) and a collection \(\alpha_1, \alpha_2, \cdots, \alpha_n\) of ordinals so that \(x \in V_\beta\) and there is a first-order formula \(\varphi\) such that, for all \(y \in V_\beta\), \(y = x\) iff \(V_\beta \models \varphi(y, \alpha_1, \alpha_2, \cdots, \alpha_n)\). In other words, it is definable at some ini..."
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