The structure of pleasant ideals
英文摘要：
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.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
