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In mathematical set theory, an Ulam matrix is an array of subsets of a cardinal number with certain properties. Ulam matrices were introduced by in his work on measurable cardinals: they may be used, for example, to show that a real-valued measurable cardinal is weakly inaccessible.〔 〕 ==Definition== Suppose that κ and λ are cardinal numbers, and let ''F'' be a λ-complete filter on λ. An Ulam matrix is a collection of subsets ''A''αβ of λ indexed by α in κ, β in λ such that *If β is not γ then ''A''αβ and ''A''αγ are disjoint. *For each β the union of the sets ''A''αβ is in the filter ''F''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ulam matrix」の詳細全文を読む スポンサード リンク
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