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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...

A note on the intersection ideal 𝒩

Tomasz Weiss (2013)

Commentationes Mathematicae Universitatis Carolinae

We prove among other theorems that it is consistent with Z F C that there exists a set X 2 ω which is not meager additive, yet it satisfies the following property: for each F σ measure zero set F , X + F belongs to the intersection ideal 𝒩 .

A note on the structure of WUR Banach spaces

Spiros A. Argyros, Sophocles Mercourakis (2005)

Commentationes Mathematicae Universitatis Carolinae

We present an example of a Banach space E admitting an equivalent weakly uniformly rotund norm and such that there is no Φ : E c 0 ( Γ ) , for any set Γ , linear, one-to-one and bounded. This answers a problem posed by Fabian, Godefroy, Hájek and Zizler. The space E is actually the dual space Y * of a space Y which is a subspace of a WCG space.

A note on Tsirelson type ideals

Boban Veličković (1999)

Fundamenta Mathematicae

Using Tsirelson’s well-known example of a Banach space which does not contain a copy of c 0 or l p , for p ≥ 1, we construct a simple Borel ideal I T such that the Borel cardinalities of the quotient spaces P ( ) / I T and P ( ) / I 0 are incomparable, where I 0 is the summable ideal of all sets A ⊆ ℕ such that n A 1 / ( n + 1 ) < . This disproves a “trichotomy” conjecture for Borel ideals proposed by Kechris and Mazur.

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