Random-cluster critical probability ($p_c(q)$)

The threshold for the origin to have an infinite percolation cluster under a consistently chosen infinite-volume random-cluster measure, conventionally the wired measure: $p_c(q)=\inf \{p:{\theta }^{\mathrm{w}}(p,q)>0\}$. The definition alone makes no assertion about percolation exactly at the threshold.

The finite-volume random-cluster weight monotonicity passes to consistently wired or free infinite-volume measures for finite increasing connection events. Decreasing these events to origin-to-infinity connectivity yields $\theta (p,q_1)\ge \theta (p,q_2)$ for $q_1\le q_2$. The corresponding supercritical parameter sets are nested, and hence $p_c(q_1)\le p_c(q_2)$.