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arXiv math/9605235math.LOmath.GN
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布尔代数的更多构造

More Constructions for Boolean algebras

Saharon Shelah

摘要:

我们解决了一些问题的布尔代数。例如,我们在ZFC中对任意的BA B和基数kappa BA B_1,B_2构造B的扩充,使得B_1,B_2在B上的自由积的深度严格大于B_1的深度,B_2的深度严格大于kappa。我们给出一个条件(对于λ,μ和θ),它意味着对于某些BA A_θ,存在B_1=B^1_{λ,μ,θ}和B_2B^2_{λ,μ,θ},使得深度(B_t)<= μ和深度(B_1 oplus_{A_theta} B_1)>= λ。然后,我们研究了对固定的A,存在这样的B_1,B_2,给出了充分和必要条件,包括相容性结果。进一步我们证明了,例如,如果B是一个BA的基数λ,λ>= μ和λ,μ是强极限奇异的相同的共尾性,那么B有一个同态像的基数μ(和μ超滤子)。接下来,我们证明对于BA B,如果d(B)^kappa < |B|,则ind(B)> kappa或Depth(B)>= log(|B|)。最后证明了如果square_lambda成立且lambda = lambda^{aleph_0},则对某些BAs B_n,Depth(B_n)<= lambda,但对Ω上的任何一致超滤子D,prod_{n< omega} B_n/D有depth >= lambda^+ .

英文摘要:

We address a number of problems on Boolean Algebras. For example, we construct, in ZFC, for any BA B, and cardinal kappa BAs B_1,B_2 extending B such that the depth of the free product of B_1,B_2 over B is strictly larger than the depths of B_1 and of B_2 than kappa. We give a condition (for lambda, mu and theta) which implies that for some BA A_theta there are B_1=B^1_{lambda, mu, theta} and B_2B^2_{lambda, mu, theta} such that Depth (B_t) <= mu and Depth (B_1 oplus_{A_theta} B_1) >= lambda. We then investigate for a fixed A, the existence of such B_1,B_2 giving sufficient and necessary conditions, involving consistency results. Further we prove that e.g. if B is a BA of cardinality lambda, lambda >= mu and lambda, mu are strong limit singular of the same cofinality, then B has a homomorphic image of cardinality mu (and with mu ultrafilters). Next we show that for a BA B, if d(B)^kappa <|B| then ind (B)> kappa or Depth (B) >= log (|B|). Finally we prove that if square_lambda holds and lambda = lambda^{aleph_0} then for some BAs B_n, Depth (B_n) <= lambda but for any uniform ultrafilter D on omega, prod_{n< omega} B_n/D has depth >= lambda^+ .

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