8 found
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  1.  25
    On L∞Κ-Free Boolean Algebras.Sakaé Fuchino, Sabine Koppelberg & Makoto Takahashi - 1992 - Annals of Pure and Applied Logic 55 (3):265-284.
    We study L∞κ-freeness in the variety of Boolean algebras. It is shown that some of the theorems on L∞κ-free algebras which are known to hold in varieties such as groups, abelian groups etc. are also true for Boolean algebras. But we also investigate properties such as the ccc of L∞κ-free Boolean algebras which have no counterpart in the varieties above.
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  2.  19
    Partial Orderings with the Weak Freese-Nation Property.Sakaé Fuchino, Sabine Koppelberg & Saharon Shelah - 1996 - Annals of Pure and Applied Logic 80 (1):35-54.
    A partial ordering P is said to have the weak Freese-Nation property if there is a mapping tf : P → [P]0 such that, for any a, b ε P, if a b then there exists c ε tf∩tf such that a c b. In this note, we study the WFN and some of its generalizations. Some features of the class of Boolean algebras with the WFN seem to be quite sensitive to additional axioms of set theory: e.g. under CH, (...)
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  3.  18
    Cardinalities of Ultraproducts of Finite Sets.Sabine Koppelberg - 1980 - Journal of Symbolic Logic 45 (3):574-584.
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  4.  9
    On< I> L_< Sub>∞ Κ-Free Boolean Algebras.Sakaé Fuchino, Sabine Koppelberg & Makoto Takahashi - 1992 - Annals of Pure and Applied Logic 55 (3):265-284.
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  5.  39
    Homogeneous Boolean Algebras with Very Nonsymmetric Subalgebras.Sabine Koppelberg & J. Donald Monk - 1983 - Notre Dame Journal of Formal Logic 24 (3):353-356.
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  6.  37
    A Boolean Ultrapower Which is Not an Ultrapower.Bernd Koppelberg & Sabine Koppelberg - 1976 - Journal of Symbolic Logic 41 (1):245-249.
  7.  12
    A Construction of Boolean Algebras From First-Order Structures.Sabine Koppelberg - 1993 - Annals of Pure and Applied Logic 59 (3):239-256.
    We give a construction assigning classes of Boolean algebras to first-order theories; several classes of Boolean algebras considered previously in the literature can be thus obtained. In particular it turns out that the class of semigroup algebras can be defined in this way, in fact by a Horn theory, and it is the largest class of Boolean algebras defined by a Horn theory.
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  8.  6
    A Superatomic Boolean Algebra with Few Automorphisms.Matatyahu Rubin & Sabine Koppelberg - 2001 - Archive for Mathematical Logic 40 (2):125-129.
    Assuming GCH, we prove that for every successor cardinal μ > ω1, there is a superatomic Boolean algebra B such that |B| = 2μ and |Aut B| = μ. Under ◊ω1, the same holds for μ = ω1. This answers Monk's Question 80 in [Mo].
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