
Diffusion of a hypothetical fluid on a graph. (A) Diffusion with source and sink. Fluid is pumped from the source into a selected set of query nodes and is allowed to leak out from each node into a sink at first-order rate γ. For clarity, an undirected network is shown. (B) Diffusion between two nodes in a directed network. Fluid diffuses in both directions according to the two edge weights between nodes i and j. A directed network is shown for generality.











