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A Note on Indestructibility and Strong Compactness

Arthur W. Apter (2008)

Bulletin of the Polish Academy of Sciences. Mathematics

If κ < λ are such that κ is both supercompact and indestructible under κ-directed closed forcing which is also (κ⁺,∞)-distributive and λ is 2 λ supercompact, then by a result of Apter and Hamkins [J. Symbolic Logic 67 (2002)], δ < κ | δ is δ⁺ strongly compact yet δ is not δ⁺ supercompact must be unbounded in κ. We show that the large cardinal hypothesis on λ is necessary by constructing a model containing a supercompact cardinal κ in which no cardinal δ > κ is 2 δ = δ supercompact, κ’s supercompactness...

A Note on Negative Tagging for Least Fixed-Point Formulae

Dilian Gurov, Bruce Kapron (2010)

RAIRO - Theoretical Informatics and Applications

Proof systems with sequents of the form U ⊢ Φ for proving validity of a propositional modal μ-calculus formula Φ over a set U of states in a given model usually handle fixed-point formulae through unfolding, thus allowing such formulae to reappear in a proof. Tagging is a technique originated by Winskel for annotating fixed-point formulae with information about the proof states at which these are unfolded. This information is used later in the proof to avoid unnecessary unfolding, without...

A note on noninterpretability in o-minimal structures

Ricardo Bianconi (1998)

Fundamenta Mathematicae

We prove that if M is an o-minimal structure whose underlying order is dense then Th(M) does not interpret the theory of an infinite discretely ordered structure. We also make a conjecture concerning the class of the theory of an infinite discretely ordered o-minimal structure.

A note on paracomplete logic

Newton C. A. da Costa, Diego Marconi (1986)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

In questa nota gli Autori descrivono nuovi sistemi di logica (detta «paracompleta») connessi con la logica della vaghezza («fuzzy logic») e con le logiche paraconsistenti.

A note on Steinhorn's omitting types theorem

Akito Tsuboi (2009)

Colloquium Mathematicae

Let p(x) be a nonprincipal type. We give a sufficient condition for a model M to have a proper elementary extension omitting p(x). As a corollary, we obtain a generalization of Steinhorn's omitting types theorem to the supersimple case.

A note on strong compactness and resurrectibility

Arthur Apter (2000)

Fundamenta Mathematicae

We construct a model containing a proper class of strongly compact cardinals in which no strongly compact cardinal ĸ is ĸ + supercompact and in which every strongly compact cardinal has its strong compactness resurrectible.

A note on strong negative partition relations

Todd Eisworth (2009)

Fundamenta Mathematicae

We analyze a natural function definable from a scale at a singular cardinal, and use it to obtain some strong negative square-brackets partition relations at successors of singular cardinals. The proof of our main result makes use of club-guessing, and as a corollary we obtain a fairly easy proof of a difficult result of Shelah connecting weak saturation of a certain club-guessing ideal with strong failures of square-brackets partition relations. We then investigate the strength of weak saturation...

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