Abstract
We study the possible order types of chains of ideals in an ordered set. Our main result is this. Given an indecomposable countable order type α, there is a finite listA α1 , ...,A α n of ordered sets such that for every ordered setP the setJ(P) of ideals ofP, ordered by inclusion, contains a chain of type α if and only ifP contains a subset isomorphic to one of theA #x03B1;1 , ...,A α n . The finiteness of the list relies on the notion of better quasi-ordering introduced by Nash-Williams and the properties of scattered chains obtained by Laver.
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Communicated by I. Rival
The results presented. here constitute the second chapter of the third cycle thesis presented by the second author before the Claude Bernard University, Lyon (July 1983).
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Pouzet, M., Zaguia, N. Ordered sets with no chains of ideals of a given type. Order 1, 159–172 (1984). https://doi.org/10.1007/BF00565651
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DOI: https://doi.org/10.1007/BF00565651