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math.LO2018
Conjugacy for homogeneous ordered graphs
Samuel Coskey, Paul Ellis
We show that for any countable homogeneous ordered graph , the conjugacy problem for automorphisms of is Borel complete. In fact we establish that each such satisfies a…
math.LO2017
The Classification Problem for Simple Unital Finite Rank Dimension Groups
Paul Ellis
The Borel complexity of the isomorphism problem for finite-rank unital simple dimension groups increases with rank. This implies that the isomorphism problems for the corresponding…