Editing Scale-free network (section)

===Features===
Many real networks are (approximately) scale-free and hence require scale-free models to describe them. In Price's scheme, there are two ingredients needed to build up a scale-free model:

1. Adding or removing [[Node (networking)|nodes]]. Usually we concentrate on growing the network, i.e. adding nodes.

2. [[Preferential attachment]]: The probability <math>\Pi</math> that new nodes will be connected to the "old" node.

Note that some models (see 
Dangalchev<ref name = "CAD" /> and
Fitness model below) can work also statically, without changing the number of nodes. It should also be kept in mind that the fact that "preferential attachment" models give rise to scale-free networks does not prove that this is the mechanism underlying the evolution of real-world scale-free networks, as there might exist different mechanisms at work in real-world systems that nevertheless give rise to scaling.