Editing Scale-free network (section)

====The Barabási–Albert model====
The [[Barabási–Albert model]], an undirected version of [[Price's model]] has a linear preferential attachment <math>\Pi(k_i)=\frac{k_i}{\sum_j k_j}</math> and adds one new node at every time step.

(Note, another general feature of <math>\Pi(k)</math> in real networks is that <math>\Pi(0)\neq 0</math>, i.e. there is a nonzero probability that a
new node attaches to an isolated node. Thus in general <math>\Pi(k)</math> has the form <math>\Pi(k)=A +k^\alpha</math>, where <math>A</math> is the initial attractiveness of the node.)