Logical laws for short existential monadic second-order sentences about graphs
Abstract
In 2001, Le Bars proved that there exists an existential monadic second-order (EMSO) sentence such that the probability that it is true on G(n,p=1/2)G(n,p=1/2) does not converge and conjectured that, for EMSO sentences with two first-order variables, the zero–one law holds. In this paper, we prove that the conjecture fails for p∈{3−√52,√5−12}p∈{3−√52,√5−12}, and give new examples of sentences with fewer variables without convergence (even for p=1/2p=1/2).