Efficiency of Information Spreading in a population of diffusing agents

We introduce a model for information spreading among a population of N agents diffusing on a square LxL lattice, starting from an informed agent (Source). Information passing from informed to unaware agents occurs whenever the relative distance is < 1. Numerical simulations show that the time required for the information to reach all agents scales as N^{-alpha}L^{beta}, where alpha and beta are noninteger. A decay factor z takes into account the degeneration of information as it passes from one agent to another; the final average degree of information of the population, I_{av}(z), is thus history-dependent. We find that the behavior of I_{av}(z) is non-monotonic with respect to N and L and displays a set of minima. Part of the results are recovered with analytical approximations.