布尔代数中独立性的变式
Variations of Independence in Boolean Algebras
摘要:
我们给出了推广自由布尔代数的几类布尔代数的定义,它们满足一个泛性质,即某些函数可推广到同态。我们给出了这类代数的生成集的一个组合性质,称之为n -独立的.研究了这些类(n-free和omega-free布尔代数)的性质。这些包括连接到超图理论和基数不变量对这些代数。引入并研究了相关的基数函数nInd,它是n-独立子集基数的上确界; i_n,极大n -独立子集的最小尺寸; i_omega,omega-独立子集的最小尺寸。P(omega)/fin上的i_n和i_omega的值与ZFC无关。同时考虑了理想独立性,证明了无穷布尔代数的基数函数p <= s_mm.我们还定义和考虑适度生成的布尔代数,即那些布尔代数,有一个生成集的元素,分裂的布尔代数的许多元素。
英文摘要:
We give a definition of some classes of boolean algebras generalizing free boolean algebras; they satisfy a universal property that certain functions extend to homomorphisms. We give a combinatorial property of generating sets of these algebras, which we call n -independent. The properties of these classes (n-free and omega-free boolean algebras) are investigated. These include connections to hypergraph theory and cardinal invariants on these algebras. Related cardinal functions, n Ind, which is the supremum of the cardinalities of n-independent subsets; i_n, the minimum size of a maximal n -independent subset; and i_omega, the minimum size of an omega-independent subset, are introduced and investigated. The values of i_n and i_omega on P(omega)/fin are shown to be independent of ZFC. Ideal-independence is also considered, and it is shown that the cardinal function p <= s_mm for infinite boolean algebras. We also define and consider moderately generated boolean algebras; that is, those boolean algebras that have a generating set consisting of elements that split finitely many elements of the boolean algebra.
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