科研之友
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摘要
We prove that, in any fine structural extender model with Jensen's lambda-indexing, there is a square(kappa(+))-sequence if and only if there is a pair of stationary subsets of kappa(+) boolean AND cof(< kappa) without common reflection point of cofinality < kappa which, in turn, is equivalent to the existence of a family of size < kappa of stationary subsets of kappa(+) boolean AND cof(< kappa) without common reflection point of cofinality < kappa. By a result of Burke/Jensen, square(kappa) fails whenever. is a subcompact cardinal. Our result shows that in extender models, it is still possible to construct a canonical square(kappa(+))-sequence where. is the first subcompact.
- 出版日期2013-2
