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HOMOGENEITY AND FIX-POINTS: GOING FORTH!

Published online by Cambridge University Press:  22 April 2015

ROGER VILLEMAIRE
ROGER VILLEMAIRE*
Affiliation:
DEPARTMENT OF COMPUTER SCIENCE UNIVERSITÉ DU QUÉBEC À MONTRÉAL C.P. 8888, SUCC. CENTRE-VILLE MONTRÉAL, QUÉBEC, H3C 3P8, CANADAE-mail: [email protected]: http://intra.info.uqam.ca/personnels/Members/villemaire_r
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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, the mapping is constructed in a single 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 for which Forth always builds an automorphism. This generalises results by Cameron and McLeish.

Keywords

homogeneous structuresback-and-forthcategoricityfix-points
Type
Articles
Information
The Journal of Symbolic Logic , Volume 80 , Issue 2 , June 2015 , pp. 636 - 660
Copyright
Copyright © The Association for Symbolic Logic 2015 

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