(a) The asymmetric link dynamics produces a broad connectivity distribution. The model prediction of the connectivity distribution of nodes with non-zero connectivity agrees well with yeast protein interaction data (filled diamonds). The solution of the rate equation (4) is shown as a solid line, the result of a computer simulation emulating the link dynamics encapsulated in (4) for a network of finite size is shown as circles (°). Nodes with the highest k (lower right) occur only once in the network. (b) High-connectivity vertices are preferentially connected to low-connectivity vertices, as also observed empirically. The figure shows the relative likelihood of the link distribution and the 'null distribution' of an uncorrelated random network, see text.