The groupoid approach to equilibrium states on right LCM semigroup C*-algebras

Given a right LCM semigroup $S$ and a homomorphism $N\colon S\to[1,+\infty)$, we use the groupoid approach to study the KMS$_\beta$-states on $C^*(S)$ with respect to the dynamics induced by $N$. We establish necessary and sufficient conditions for the existence and uniqueness of KMS$_\beta$-states. As an application, we show that the sufficient condition for the uniqueness obtained for so-called generalized scales is necessary as well. Our most complete results are obtained for inverse temperatures $\beta$ at which the $\zeta$-function of $N$ is finite. In this case we get an explicit bijective correspondence between the KMS$_\beta$-states on $C^*(S)$ and the tracial states on $C^*(\operatorname{ker} N)$.