Fodor's lemma: Revision history

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29 August 2023

16 October 2022

  • curprev 02:5502:55, 16 October 2022‎ C7X talk contribs‎ 1,263 bytes +33‎ No edit summary undo Tag: Visual edit
  • curprev 02:5302:53, 16 October 2022‎ C7X talk contribs‎ 1,230 bytes +1,230‎ Created page with "'''Fodor's lemma''' (or the '''pressing-down lemma''') is a lemma proven by Géza Fodor in 1956. The lemma states that when \(\kappa\) is an uncountable regular cardinal and \(S\) is a stationary set of ordinals \(<\kappa\), any regressive function \(f:S\to\{<\kappa\}\) must be constant on a stationary set of ordinals \(<\kappa\). ==Importance to apierology== Since \(\omega_1\) is regular, setting \(S=\{<\omega_1\}\), Fodor's lemma implies there does not exist a fundame..."
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