Phase Transitions in the Quadratic Contact Process on Complex Networks

The quadratic contact process (QCP) is a natural extension of the well studied linear contact process where infected (1) individuals infect susceptible (0) neighbors at rate $lambda$ and infected individuals recover ($1 longrightarrow 0$) at rate 1. In the QCP, a combination of two 1s is required to effect a $0 longrightarrow 1$ change. We extend the study of the QCP, which so far has been limited to lattices, to complex networks. comment{as a model for the change in a population through sexual reproduction and death.} We define t