Bodirsky, Manuel, Bradley-Williams, David, Pinsker, Michael and Pongracz, Andras (2015) The Universal Homogenous Binary Tree. ArXiv.org .
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Official URL: http://arxiv.org/abs/1409.2170
A partial order is called semilinear i� the upper bounds of each element are linearly ordered and any two elements have a common upper bound. There exists, up to isomorphism, a unique countable existentially closed semilinear order, which we denote by (S2;�). We study the reducts of (S2;�), that is, the relational structures with domain S2, all of whose relations are �rst-order de�nable in (S2;�). Our main result is a classi�cation of the model-complete cores of the reducts of S2. From this, we also obtain a classi�cation of reducts up to �rst-order interde�nability, which is equivalent to a classifi�cation of all closed permutation groups that contain the automorphism group of (S2;�).
|Subjects:||Mathematics > Pure mathematics|
|Schools:||Faculty of Science and Technology > School of Physical Sciences and Computing|
|Deposited By:||Helen Cooper|
|Deposited On:||19 Feb 2016 11:23|
|Last Modified:||20 Oct 2016 15:24|
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