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Ben-Zion Weltsch

Publications and source records attributed to Ben-Zion Weltsch.

2 recordsLinked to original sources

On the Intermediate Models of Strongly Compact Prikry Forcing

We analyze the intermediate models of the strongly compact Prikry forcing. We exhibit a simple combinatorial property which, for a given supercompact cardinal $κ$, characterize the projections of all projections of the strongly compact Prikry forcing using $κ$-complete fine measures. Considering level-by-level results, if $κ$ is $2^λ$-strongly compact, we characterize the forcings of size $\leqλ$ which are projections of that $λ$-strongly compact Prikry forcing. Our characterization generalizes several known results, including those of Benhamou-Hayut-Gitik and folklore results regarding the class of $κ$-distributive forcing notions which are embedded into the supercompact Prikry forcing. Fixing a $κ$-complete fine measure $\mathcal{U}$ on $P_κ(λ)$, we also provide Rudin-Keisler like critiria for the existence projections from the strongly compact Prikry forcing with $\mathcal{U}$. Finally, we prove that among all projections of the $λ$-strongly compact Prikry forcing, the class of forcings of cardinality $λ$ are exactly those for which there is a projection map which depends only on the stem of the Prikry condition. We also give partial results regarding projections of arbitrary cardinality.

math.LO

Supercompact Measures and the Galvin Property

We study saturation properties of $σ$-complete measures on $P_κ(λ)$, where $λ$ can be either regular or singular. In particular, we prove that in contrast to Galvin's theorem, the Galvin property of Benhamou-Garti-Poveda fails for normal fine ultrafilters on $P_κ(λ)$, answering a question of the first author and Goldberg. We then provide several applications of our results: to ultrafilters on successor cardinals under $UA$, we generalize a result of Gitik regarding density of ground model sets in supercompact Prikry extensions, and to generating sets of $P_κ(λ)$ measures. In the second part of the paper, we study variations of the Galvin property suitable for ultrafilters over $P_κ(λ)$, and generalize a result of Foreman-Magidor-Zeman on determinacy of filter games to the two-cardinal setting, answering a question of the first author and Gitman.

math.LO