An effective characterization of the alternation hierarchy in two-variable logic
Logic in Computer Science
2012-05-23 v1
Abstract
We characterize the languages in the individual levels of the quantifier alternation hierarchy of first-order logic with two variables by identities. This implies decidability of the individual levels. More generally we show that the two-sided semidirect product of a decidable variety with the variety J is decidable.
Cite
@article{arxiv.1205.4802,
title = {An effective characterization of the alternation hierarchy in two-variable logic},
author = {Andreas Krebs and Howard Straubing},
journal= {arXiv preprint arXiv:1205.4802},
year = {2012}
}