On the Influence of Confluence in Modal Logics.

In this paper we prove that adding a confluence axiom to a modal logic which behaves rather well from the viewpoint of complexity of the satisfaction problem, drastically increases its complexity and blows it up from PSPACE-completeness to NEXPTIME-completeness. More precisely, we investigate here both monomodal K + confluence and bimodal K with confluence between the two modalities. [ABSTRACT FROM AUTHOR]