Abstract:
We study hard-core (HC) models on Cayley trees. Given a $2$-state HC-model, we prove that exactly two weakly periodic (aperiodic) Gibbs measures exist under certain conditions on the parameters. Moreover, we consider fertile $4$-state HC-models with the activity parameter $\lambda>0$. The three types of these models are known to exist. For one of the models we show that the translationinvariant Gibbs measure is not unique.