Motivated by results of Henry, Pralat and Zhang (PNAS 108.21 (2011): 8605-8610), we propose a general scheme for evolving spatial networks in order to reduce their total edge lengths. We study the properties of the equilbria of two networks from this
class, which interpolate between three well studied objects: the ErdH{o}s-R{e}nyi random graph, the random geometric graph, and the minimum spanning tree. The first of our two evolutions can be used as a model for a social network where individuals have fixed opinions about a number of issues and adjust their ties to be connected to people with similar views. The second evolution which preserves the connectivity of the network has potential applications in the design of transportation networks and other distribution systems.
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
