Misc,

Asymptotic Behavior of Aldous' Gossip Process

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(2010)cite arxiv:1005.1608.

Abstract

Aldous (2007) defined a gossip process in which space is a discrete $N \times N$ torus, and the state of the process at time $t$ is the set of individuals who know the information. Information spreads from a site to its nearest neighbors at rate 1/4 each and at rate $N^-\alpha$ to a site chosen at random from the torus. We will be interested in the case in which $< 3$, where the long range transmission significantly accelerates the time at which everyone knows the information. We prove three results that precisely describe the spread of information in a slightly simplified model on the real torus. The time until everyone knows the information is asymptotically $T=(2-2\alpha/3) N^\alpha/3 N$. If $\rho_s$ is the fraction of the population who know the information at time $s$ and $\ep$ is small then, for large $N$, the time until $\rho_s$ reaches $\ep$ is $T(\ep) T + N^\alpha/3 łog(3\ep/M)$, where $M$ is a random variable determined by the early spread of the information. The value of $\rho_s$ at time $s = T(1/3) + t N^\alpha/3$ is almost a deterministic function $h(t)$ which satisfies an odd looking integro-differential equation. The last result confirms a heuristic calculation of Aldous.

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