A covering lemma for HOD of \(K(\mathbb R)\) (Q609760)

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scientific article; zbMATH DE number 5822355
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A covering lemma for HOD of \(K(\mathbb R)\)
scientific article; zbMATH DE number 5822355

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    A covering lemma for HOD of \(K(\mathbb R)\) (English)
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    1 December 2010
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    This is the third in the series of the author's articles on covering lemmas for inner models. In the first of the series [Arch. Math. Logic 41, No.~1, 49--54 (2002; Zbl 1022.03031)], the author developed the covering lemmas for \(L({\mathbb R})\), as well as \(\text{HOD}^{L({\mathbb R})}\), under the assumption of \(\text{ZF}+\text{AD}\) and the nonexistence of \({\mathbb R}^\sharp\). In the second [Arch. Math. Logic 46, No. 3--4, 197--221 (2007; Zbl 1110.03044)] and this paper, the author generalizes these results to an inner model called \(K({\mathbb R})\). \(K({\mathbb R})\) is built with mice that are associated to \({\mathbb R}\)-complete measures, and is less general than Steel's \(\mathbf{K}({\mathbb R})\), which is built with mice that are associated to sequence of extenders. This paper proves the covering lemma for \(\text{HOD}^{K({\mathbb R})}\). The main theorem states that under \(\text{ZF}+\text{AD}\) and the nonexistence of an inner model with \({\mathbb R}\)-complete measurable cardinals, every set of reals of size \(\geq \Theta\) (the supremum of the ordinals that are the surjective images of \({\mathbb R}\)) can be covered by one in \(\text{HOD}^{K({\mathbb R})}\) of the same size. A key ingredient of the argument is the version of a theorem of Woodin's adapted to \(K({\mathbb R})\), more precisely, \(K({\mathbb R})\) is a symmetric generic extension of its own \(\text{HOD}\). Though this follows from Steel's analysis for \(\mathbf{K}({\mathbb R})\), the author provides his own arguments. As a corollary, the author obtains that, assuming \(\text{ZF}+\text{AD}\), the existence of an inner model with \({\mathbb R}\)-complete measurable cardinals is equivalent to the existence of a set of ordinals that has size \(\geq \Theta^{K({\mathbb R})}\) but no covering set in \(\text{HOD}^{K({\mathbb R})}\).
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    descriptive set theory
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    determinacy
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    fine structure
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