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Some Remarks on Tall Cardinals and Failures of GCH

Arthur W. Apter (2013)

Bulletin of the Polish Academy of Sciences. Mathematics

We investigate two global GCH patterns which are consistent with the existence of a tall cardinal, and also present some related open questions.

Spectra of uniformity

Yair Hayut, Asaf Karagila (2019)

Commentationes Mathematicae Universitatis Carolinae

We study some limitations and possible occurrences of uniform ultrafilters on ordinals without the axiom of choice. We prove an Easton-like theorem about the possible spectrum of successors of regular cardinals which carry uniform ultrafilters; we also show that this spectrum is not necessarily closed.

Stationary reflection and level by level equivalence

Arthur W. Apter (2009)

Colloquium Mathematicae

We force and construct a model in which level by level equivalence between strong compactness and supercompactness holds, along with certain additional “inner model like” properties. In particular, in this model, the class of Mahlo cardinals reflecting stationary sets is the same as the class of weakly compact cardinals, and every regular Jónsson cardinal is weakly compact. On the other hand, we force and construct a model for the level by level equivalence between strong compactness and supercompactness...

Strong compactness, measurability, and the class of supercompact cardinals

Arthur W. Apter (2001)

Fundamenta Mathematicae

We prove two theorems concerning strong compactness, measurability, and the class of supercompact cardinals. We begin by showing, relative to the appropriate hypotheses, that it is consistent non-trivially for every supercompact cardinal to be the limit of (non-supercompact) strongly compact cardinals. We then show, relative to the existence of a non-trivial (proper or improper) class of supercompact cardinals, that it is possible to have a model with the same class of supercompact cardinals in...

Strong Fubini axioms from measure extension axioms

Piotr Zakrzewski (1992)

Commentationes Mathematicae Universitatis Carolinae

It is shown that measure extension axioms imply various forms of the Fubini theorem for nonmeasurable sets and functions in Radon measure spaces.

Strong Fubini properties for measure and category

Krzysztof Ciesielski, Miklós Laczkovich (2003)

Fundamenta Mathematicae

Let (FP) abbreviate the statement that 0 1 ( 0 1 f d y ) d x = 0 1 ( 0 1 f d x ) d y holds for every bounded function f: [0,1]² → ℝ whenever each of the integrals involved exists. We shall denote by (SFP) the statement that the equality above holds for every bounded function f: [0,1]² → ℝ having measurable vertical and horizontal sections. It follows from well-known results that both of (FP) and (SFP) are independent of the axioms of ZFC. We investigate the logical connections of these statements with several other strong Fubini type properties...

Strong meager properties for filters

Claude Laflamme (1995)

Fundamenta Mathematicae

We analyze several “strong meager” properties for filters on the natural numbers between the classical Baire property and a filter being F σ . Two such properties have been studied by Talagrand and a few more combinatorial ones are investigated. In particular, we define the notion of a P⁺-filter, a generalization of the traditional concept of P-filter, and prove the existence of a non-meager P⁺-filter. Our motivation lies in understanding the structure of filters generated by complements of members...

Stronger ideals over κ λ

Yo Matsubara (2002)

Fundamenta Mathematicae

In §1 we define some properties of ideals by using games. These properties strengthen precipitousness. We call these stronger ideals. In §2 we show some limitations on the existence of such ideals over κ λ . We also present a consistency result concerning the existence of such ideals over κ λ . In §3 we show that such ideals satisfy stronger normality. We show a cardinal arithmetical consequence of the existence of strongly normal ideals. In § 4 we study some “large cardinal-like” consequences of stronger...

Strongly almost disjoint familes, revisited

A. Hajnal, Istvan Juhász, Saharon Shelah (2000)

Fundamenta Mathematicae

The relations M(κ,λ,μ) → B [resp. B(σ)] meaning that if A [ κ ] λ with |A|=κ is μ-almost disjoint then A has property B [resp. has a σ-transversal] had been introduced and studied under GCH in [EH]. Our two main results here say the following: Assume GCH and let ϱ be any regular cardinal with a supercompact [resp. 2-huge] cardinal above ϱ. Then there is a ϱ-closed forcing P such that, in V P , we have both GCH and M ( ϱ ( + ϱ + 1 ) , ϱ + , ϱ ) B [resp. M ( ϱ ( + ϱ + 1 ) , λ , ϱ ) B ( ϱ + ) for all λ ϱ ( + ϱ + 1 ) ] . These show that, consistently, the results of [EH] are sharp. The necessity...

Supercompactness and failures of GCH

Sy-David Friedman, Radek Honzik (2012)

Fundamenta Mathematicae

Let κ < λ be regular cardinals. We say that an embedding j: V → M with critical point κ is λ-tall if λ < j(κ) and M is closed under κ-sequences in V. Silver showed that GCH can fail at a measurable cardinal κ, starting with κ being κ⁺⁺-supercompact. Later, Woodin improved this result, starting from the optimal hypothesis of a κ⁺⁺-tall measurable cardinal κ. Now more generally, suppose that κ ≤ λ are regular and one wishes the GCH to fail at λ with κ being λ-supercompact. Silver’s methods show...

Supercompactness and partial level by level equivalence between strong compactness and strongness

Arthur W. Apter (2004)

Fundamenta Mathematicae

We force and construct a model containing supercompact cardinals in which, for any measurable cardinal δ and any ordinal α below the least beth fixed point above δ, if δ + α is regular, δ is δ + α strongly compact iff δ is δ + α + 1 strong, except possibly if δ is a limit of cardinals γ which are δ + α strongly compact. The choice of the least beth fixed point above δ as our bound on α is arbitrary, and other bounds are possible.

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