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Proper Forcing, Cardinal Arithmetic, and Uncountable Linear Orders
Published online by Cambridge University Press: 15 January 2014
Abstract
In this paper I will communicate some new consequences of the Proper Forcing Axiom. First, the Bounded Proper Forcing Axiom implies that there is a well ordering of ℝ which is Σ1-definable in (H(ω2), ϵ). Second, the Proper Forcing Axiom implies that the class of uncountable linear orders has a five element basis. The elements are X, ω1, , C, C * where X is any suborder of the reals of size ω1 and C is any Countryman line. Third, the Proper Forcing Axiom implies the Singular Cardinals Hypothesis at k unless stationary subsets of reflect. The techniques are expected to be applicable to other open problems concerning the theory ofH(ω2).
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- Copyright © Association for Symbolic Logic 2005
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