Deciding whether the ordering is necessary in a Presburger formula
Authors: Christian Choffrut 1; Achille Frigeri 1,2
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Christian Choffrut;Achille Frigeri
1 Laboratoire d'informatique Algorithmique : Fondements et Applications
2 Dipartimento di Matematica, "Francesco Brioschi"
We characterize the relations which are first-order definable in the model of the group of integers with the constant 1. This allows us to show that given a relation defined by a first-order formula in this model enriched with the usual ordering, it is recursively decidable whether or not it is first-order definable without the ordering.