4 citations · 4 across the 4 of their papers we have counts for
4 papers
Subalgebras of Cohen algebras need not be Cohen
Sabine Koppelberg, Saharon Shelah
We give an example of a regular and complete subalgebra of a Cohen algebra which is not Cohen.
Partial orderings with the weak Freese-Nation property
Sakaé Fuchino, Sabine Koppelberg, Saharon Shelah
A partial ordering P is said to have the weak Freese-Nation property (WFN) if there is a mapping f:P ---> [P]^{<= aleph_0} such that, for any a, b in P, if a <= b then there exists…
A game on partial orderings
Sakaé Fuchino, Sabine Koppelberg, Saharon Shelah
We study the determinacy of the game G_kappa (A) introduced in [FKSh:549] for uncountable regular kappa and several classes of partial orderings A. Among trees or Boolean algebras,…
Densities of ultraproducts of Boolean algebras
Sabine Koppelberg, Saharon Shelah
We answer three problems by J. D. Monk on cardinal invariants of Boolean algebras. Two of these are whether taking the algebraic density pi(A), resp. the topological density d(A),…