Oriented site percolation ($p_c^{\mathrm{site}}$)

Independently open vertices of a directed graph with common probability $p$, and require every vertex of an infinite directed path to be open, including its root. Conditioning the root to be open changes the survival probability by a factor $p$ and does not change the critical probability. This model gives an independent comparison process in the independent oriented-percolation comparison for the contact process.