KMS quantum symmetric states (1609.01225v1)

Abstract: Let $A$ be a unital C$^*$-algebra and let $\sigma$ be a one-parameter automorphism group of $A$. We consider $\operatorname{QSS}\sigma(A)$, the set of all quantum symmetric states on $_1^\infty A$ that are also KMS states (for a fixed inverse temperature, for specificity taken to be $-1$) for the free product automorphism group $_1^\infty\sigma$. We characterize the elements of $\operatorname{QSS}\sigma(A)$, we show that $\operatorname{QSS}_\sigma(A)$ is a Choquet simplex whenever it is nonempty and we characterize its extreme points.