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  1. Decomposable Ultrafilters and Possible Cofinalities.Paolo Lipparini - 2008 - Notre Dame Journal of Formal Logic 49 (3):307-312.
    We use Shelah's theory of possible cofinalities in order to solve some problems about ultrafilters. Theorem: Suppose that $\lambda$ is a singular cardinal, $\lambda ' \lessthan \lambda$, and the ultrafilter $D$ is $\kappa$ -decomposable for all regular cardinals $\kappa$ with $\lambda '\lessthan \kappa \lessthan \lambda$. Then $D$ is either $\lambda$-decomposable or $\lambda ^+$-decomposable. Corollary: If $\lambda$ is a singular cardinal, then an ultrafilter is ($\lambda$,$\lambda$)-regular if and only if it is either $\operator{cf} \lambda$-decomposable or $\lambda^+$-decomposable. We also give applications to (...)
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  • Cardinal functions on ultra products of Boolean algebras.Douglas Peterson - 1997 - Journal of Symbolic Logic 62 (1):43-59.
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  • Canonical functions, non-regular ultrafilters and Ulam’s problem on ω1.Oliver Deiser & Dieter Donder - 2003 - Journal of Symbolic Logic 68 (3):713-739.
    Our main results are:Theorem 1. Con implies Con. [In fact equiconsistency holds.]Theorem 3. Con implies Con.Theorem 5. Con ”) implies Con.We start with a discussion of the canonical functions and look at some combinatorial principles. Assuming the domination property of Theorem 1, we use the Ketonen diagram to show that ω2V is a limit of measurable cardinals in Jensen’s core model KMO for measures of order zero. Using related arguments we show that ω2V is a stationary limit of measurable cardinals (...)
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  • Limit ultrapowers and abstract logics.Paolo Lipparini - 1987 - Journal of Symbolic Logic 52 (2):437-454.
    We associate with any abstract logic L a family F(L) consisting, intuitively, of the limit ultrapowers which are complete extensions in the sense of L. For every countably generated [ω, ω]-compact logic L, our main applications are: (i) Elementary classes of L can be characterized in terms of $\equiv_L$ only. (ii) If U and B are countable models of a countable superstable theory without the finite cover property, then $\mathfrak{U} \equiv_L \mathfrak{B}$ . (iii) There exists the "largest" logic M such (...)
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  • (1 other version)Square in core models.Ernest Schimmerling & Martin Zeman - 2001 - Bulletin of Symbolic Logic 7 (3):305-314.
    We prove that in all Mitchell-Steel core models, □ κ holds for all κ. (See Theorem 2.). From this we obtain new consistency strength lower bounds for the failure of □ κ if κ is either singular and countably closed, weakly compact, or measurable. (Corallaries 5, 8, and 9.) Jensen introduced a large cardinal property that we call subcompactness; it lies between superstrength and supercompactness in the large cardinal hierarchy. We prove that in all Jensen core models, □ κ holds (...)
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  • The Axiom of Determinacy, Forcing Axioms, and the Nonstationary Ideal.W. Hugh Woodin - 2002 - Bulletin of Symbolic Logic 8 (1):91-93.
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  • Regularity of Ultrafilters and the Core Model.Hans-Dieter Donder, Peter Koepke, Jean-Pierre Levinski & D. J. Walker - 1990 - Journal of Symbolic Logic 55 (3):1313-1315.
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  • Models and Ultraproducts: An Introduction.J. L. Bell & A. B. Slomson - 1972 - Journal of Symbolic Logic 37 (4):763-764.
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  • Indecomposable ultrafilters over small large cardinals.Michael Sheard - 1983 - Journal of Symbolic Logic 48 (4):1000-1007.
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  • Finest partitions for ultrafilters.Akihiro Kanamori - 1986 - Journal of Symbolic Logic 51 (2):327-332.
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  • The weak □* is really weaker than the full □.Shai Ben-David & Menachem Magidor - 1986 - Journal of Symbolic Logic 51 (4):1029 - 1033.
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  • Exactly controlling the non-supercompact strongly compact cardinals.Arthur W. Apter & Joel David Hamkins - 2003 - Journal of Symbolic Logic 68 (2):669-688.
    We summarize the known methods of producing a non-supercompact strongly compact cardinal and describe some new variants. Our Main Theorem shows how to apply these methods to many cardinals simultaneously and exactly control which cardinals are supercompact and which are only strongly compact in a forcing extension. Depending upon the method, the surviving non-supercompact strongly compact cardinals can be strong cardinals, have trivial Mitchell rank or even contain a club disjoint from the set of measurable cardinals. These results improve and (...)
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  • Regularity properties of ideals and ultrafilters.Alan D. Taylor - 1979 - Annals of Mathematical Logic 16 (1):33.
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  • Applications of PCF theory.Saharon Shelah - 2000 - Journal of Symbolic Logic 65 (4):1624-1674.
    We deal with several pcf problems: we characterize another version of exponentiation: maximal number of κ-branches in a tree with λ nodes, deal with existence of independent sets in stable theories, possible cardinalities of ultraproducts and the depth of ultraproducts of Boolean Algebras. Also we give cardinal invariants for each λ with a pcf restriction and investigate further T D (f). The sections can be read independently, although there are some minor dependencies.
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  • (1 other version)Square In Core Models, By, Pages 305 -- 314.Ernest Schimmerling & Martin Zeman - 2001 - Bulletin of Symbolic Logic 7 (3):305-314.
    We prove that in all Mitchell-Steel core models, □k holds for all k. From this we obtain new consistency strength lower bounds for the failure of □k if k is either singular and countably closed, weakly compact, or measurable. Jensen introduced a large cardinal property that we call subcompactness; it lies between superstrength and supercompactness in the large cardinal hierarchy. We prove that in all Jensen core models, □k holds iff k is not subcompact.
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  • Ultrafilter translations.Paolo Lipparini - 1996 - Archive for Mathematical Logic 35 (2):63-87.
    We develop a method for extending results about ultrafilters into a more general setting. In this paper we shall be mainly concerned with applications to cardinality logics. For example, assumingV=L, Gödel's Axiom of Constructibility, we prove that if λ > ωα then the logic with the quantifier “there existα many” is (λ,λ)-compact if and only if either λ is weakly compact or λ is singular of cofinality<ωα. As a corollary, for every infinite cardinals λ and μ, there exists a (λ,λ)-compact (...))
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  • (1 other version)On descendingly incomplete ultrafilters.Kenneth Kunen & Karel Prikry - 1971 - Journal of Symbolic Logic 36 (4):650-652.
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  • Strong compactness and other cardinal sins.Jussi Ketonen - 1972 - Annals of Mathematical Logic 5 (1):47.
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  • Regular ultrafilters and finite square principles.Juliette Kennedy, Saharon Shelah & Jouko Väänänen - 2008 - Journal of Symbolic Logic 73 (3):817-823.
    We show that many singular cardinals λ above a strongly compact cardinal have regular ultrafilters D that violate the finite square principle $\square _{\lambda ,D}^{\mathit{fin}}$ introduced in [3]. For such ultrafilters D and cardinals λ there are models of size λ for which Mλ / D is not λ⁺⁺-universal and elementarily equivalent models M and N of size λ for which Mλ / D and Nλ / D are non-isomorphic. The question of the existence of such ultrafilters and models was (...)
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  • PFA Implies ADL(R).John R. Steel - 2005 - Journal of Symbolic Logic 70 (4):1255 - 1296.
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  • Realism, nonstandard set theory, and large cardinals.Karel Hrbacek - 2001 - Annals of Pure and Applied Logic 109 (1-2):15-48.
    Mathematicians justify axioms of set theory “intrinsically”, by reference to the universe of sets of their intuition, and “extrinsically”, for example, by considerations of simplicity or usefullness for mathematical practice. Here we apply the same kind of justifications to Nonstandard Analysis and argue for acceptance of BNST+ . BNST+ has nontrivial consequences for standard set theory; for example, it implies existence of inner models with measurable cardinals. We also consider how to practice Nonstandard Analysis in BNST+, and compare it with (...)
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  • Model-Theoretic Logics.Jon Barwise & Solomon Feferman - 2017 - Cambridge University Press.
    This book brings together several directions of work in model theory between the late 1950s and early 1980s.
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  • Canonical functions, non-regular ultrafilters and Ulam's problem on 1.Oliver Deiser & Hans-Dieter Donder - 2003 - Journal of Symbolic Logic 68 (3):713-739.
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  • (1 other version)[Omnibus Review].Akihiro Kanamori - 1981 - Journal of Symbolic Logic 46 (4):864-866.
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