Permutations on the random permutation
Logic
2014-06-03 v2 Combinatorics
Abstract
The random permutation is the Fra\"iss\'e limit of the class of finite structures with two linear orders. Answering a problem stated by Peter Cameron in 2002, we use a recent Ramsey-theoretic technique to show that there exist precisely 39 closed supergroups of the automorphism group of the random permutation, and thereby expose all symmetries of this structure. Equivalently, we classify all structures which have a first-order definition in the random permutation.
Keywords
Cite
@article{arxiv.1405.4297,
title = {Permutations on the random permutation},
author = {Julie Linman and Michael Pinsker},
journal= {arXiv preprint arXiv:1405.4297},
year = {2014}
}
Comments
18 pages