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September 2011 Classes of Ulm type and coding rank-homogeneous trees in other structures
E. Fokina, J. F. Knight, A. Melnikov, S. M. Quinn, C. Safranski
J. Symbolic Logic 76(3): 846-869 (September 2011). DOI: 10.2178/jsl/1309952523

Abstract

The first main result isolates some conditions which fail for the class of graphs and hold for the class of Abelian p-groups, the class of Abelian torsion groups, and the special class of “rank-homogeneous” trees. We consider these conditions as a possible definition of what it means for a class of structures to have “Ulm type”. The result says that there can be no Turing computable embedding of a class not of Ulm type into one of Ulm type. We apply this result to show that there is no Turing computable embedding of the class of graphs into the class of “rank-homogeneous” trees. The second main result says that there is a Turing computable embedding of the class of rank-homogeneous trees into the class of torsion-free Abelian groups. The third main result says that there is a “rank-preserving” Turing computable embedding of the class of rank-homogeneous trees into the class of Boolean algebras. Using this result, we show that there is a computable Boolean algebra of Scott rank ω1CK.

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E. Fokina. J. F. Knight. A. Melnikov. S. M. Quinn. C. Safranski. "Classes of Ulm type and coding rank-homogeneous trees in other structures." J. Symbolic Logic 76 (3) 846 - 869, September 2011. https://doi.org/10.2178/jsl/1309952523

Information

Published: September 2011
First available in Project Euclid: 6 July 2011

zbMATH: 1241.03042
MathSciNet: MR2849248
Digital Object Identifier: 10.2178/jsl/1309952523

Rights: Copyright © 2011 Association for Symbolic Logic

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Vol.76 • No. 3 • September 2011
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