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A preservation theorem for ec-structures with applications
Published online by Cambridge University Press: 12 March 2014
Abstract
We characterize the model companions of universal Horn classes generated by a two-element algebra (or ordered two-element algebra). We begin by proving that given two mutually model consistent classes M and N of
(respectively
) structures, with
,
, provided that an
-definability condition for the function and relation symbols of
holds. We use this, together with Post's characterization of ISP(A), where A is a two-element algebra, to show that the model companions of these classes essentially lie in the classes of posets and semilattices, or characteristic two groups and relatively complemented distributive lattices.
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- Research Article
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- Copyright © Association for Symbolic Logic 1987
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