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Keywords:

  • Stationary sets;
  • internally approachable models;
  • club shooting;
  • Pκλ

Abstract

For a regular cardinal κ with κ<κ = κ and κλ , we construct generically (forcing by a < κ-closed κ+-c. c. p. o.-set ℙ0) a subset S of {xPκλ : xκ is a singular ordinal} such that S is stationary in a strong sense (FIAκλ -stationary in our terminology) but the stationarity of S can be destroyed by a κ+-c. c. forcing ℙ* (in V) which does not add any new element of Pκλ . Actually ℙ* can be chosen so that ℙ* is κ-strategically closed. However we show that such ℙ* itself cannot be κ-strategically closed or even <κ-strategically closed if κ is inaccessible. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)