Two variable logic with ultimately periodic counting
Logic in Computer Science
2024-04-05 v2 Combinatorics
Abstract
We consider the extension of two variable logic with quantifiers that state that the number of elements where a formula holds should belong to a given ultimately periodic set. We show that both satisfiability and finite satisfiability of the logic are decidable. We also show that the spectrum of any sentence is definable in Presburger arithmetic. In the process we present several refinements to the ``biregular graph method''. In this method, decidability issues concerning two-variable logics are reduced to questions about Presburger definability of integer vectors associated with partitioned graphs, where nodes in a partition satisfy certain constraints on their in- and out-degrees.
Cite
@article{arxiv.2006.01193,
title = {Two variable logic with ultimately periodic counting},
author = {Michael Benedikt and Egor V. Kostylev and Tony Tan},
journal= {arXiv preprint arXiv:2006.01193},
year = {2024}
}