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HOMOGENEITY AND FIX-POINTS: GOING FORTH!

By ROGER VILLEMAIRE

Abstract

While the back-and-forth method has been often attributed to Cantor, it turns out that in the original proof of the characterisation of countable linear dense orders, themapping is constructed in a single\ud direction. Cameron has called this method Forth and has shown that it can fail to build an automorphism for some homogeneous structures.We give in this paper a characterisation of those homogeneous structures\ud for which Forth always builds an automorphism. This generalises results by Cameron and McLeish

Topics: homogeneous structures, back-and-forth, categoricity, fix-points
Year: 2015
DOI identifier: 10.1017/jsl.2014.72
OAI identifier: oai:www.archipel.uqam.ca:8149

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