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Indestructibility of generically strong cardinals

100%

Cody B., Cox S.

Fundamenta Mathematicae

2016

tom 232

nr 2

131-149

Foreman (2013) proved a Duality Theorem which gives an algebraic characterization of certain ideal quotients in generic extensions. As an application he proved that generic supercompactness of ω₁ is preserved by any proper forcing. We generalize portions of Foreman's Duality Theorem to the context of generic extender embeddings and ideal extenders (as introduced by Claverie (2010)). As an application we prove that if ω₁ is generically strong, then it remains so after adding any number of Cohen subsets of ω₁; however many other ω₁-closed posets-such as Col(ω₁,ω₂)-can destroy the generic strongness of ω₁. This generalizes some results of Gitik-Shelah (1989) about indestructibility of strong cardinals to the generically strong context. We also prove similar theorems for successor cardinals larger than ω₁.

Easton functions and supercompactness

81%

Cody B., Friedman S.-D., Honzik R.

Fundamenta Mathematicae

2014

tom 226

nr 3

279-296

Suppose that κ is λ-supercompact witnessed by an elementary embedding j: V → M with critical point κ, and further suppose that F is a function from the class of regular cardinals to the class of cardinals satisfying the requirements of Easton's theorem: (1) ∀α α < cf(F(α)), and (2) α < β ⇒ F(α) ≤ F(β). We address the question: assuming GCH, what additional assumptions are necessary on j and F if one wants to be able to force the continuum function to agree with F globally, while preserving the λ-supercompactness of κ ? We show that, assuming GCH, if F is any function as above, and in addition for some regular cardinal λ > κ there is an elementary embedding j: V → M with critical point κ such that κ is closed under F, the model M is closed under λ-sequences, H(F(λ)) ⊆ M, and for each regular cardinal γ ≤ λ one has $(|j(F)(γ)| = F(γ))^{V}$, then there is a cardinal-preserving forcing extension in which $2^{δ} = F(δ)$ for every regular cardinal δ and κ remains λ-supercompact. This answers a question of [CM14].

Ograniczanie wyników

2 Fundamenta Mathematicae

2 Cody B.

1 Cox S.

1 Friedman S.-D.

1 Honzik R.

1 2016

1 2014

Wyniki wyszukiwania

Indestructibility of generically strong cardinals

Easton functions and supercompactness