The structure of pleasant ideals

DOI10.1305/NDJFL/1094061866zbMATH Open0814.04003arXivmath/9308203OpenAlexW2072959595MaRDI QIDQ1344442

Christopher C. Leary

Publication date: 13 June 1995

Published in: Notre Dame Journal of Formal Logic (Search for Journal in Brave)

Abstract: Normal ideals on regular uncountable cardinals are familiar objects. We investigate ideals that are pleasant--while a normal ideal is closed under arbitrary diagonal unions, a pleasant ideal is closed only under diagonal unions indexed by sets that are elements of the ideal. We show any selective ideal extending the nonstationary ideal must be normal.

Full work available at URL: https://arxiv.org/abs/math/9308203

zbMATH Keywords

regular cardinalnormal idealselective idealpleasant ideals

Mathematics Subject Classification ID

Other combinatorial set theory (03E05)

Related Items (5)

From well to better, the space of ideals ⋮ Pleasant ideals ⋮ Purity and idealization: essays in honor of Mic Detlefsen. Introduction ⋮ Some consequences of reflection on the approachability ideal ⋮ The happy formalist

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