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Chainability and Hemmingsen's theorem
Authors:Taras Banakh  Paul Bankston  Brian Raines
Institution:a Department of Mathematics, L'viv National University, Ukraine
b Nipissing University, North Bay, Ontario, Canada
c Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI 53201-1881, USA
d Department of Mathematics, Baylor University, Waco, TX 76798-7328, USA
Abstract:On the surface, the definitions of chainability and Lebesgue covering dimension ?1 are quite similar as covering properties. Using the ultracoproduct construction for compact Hausdorff spaces, we explore the assertion that the similarity is only skin deep. In the case of dimension, there is a theorem of E. Hemmingsen that gives us a first-order lattice-theoretic characterization. We show that no such characterization is possible for chainability, by proving that if κ is any infinite cardinal and A is a lattice base for a nondegenerate continuum, then A is elementarily equivalent to a lattice base for a continuum Y, of weight κ, such that Y has a 3-set open cover admitting no chain open refinement.
Keywords:primary  54F15  secondary  03C20  03C65  06D05  54F45
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