Spreading of Messages in Random Graphs

  • Authors:
  • Ching-Lueh Chang;Yuh-Dauh Lyuu

  • Affiliations:
  • National Taiwan University, Department of Computer Science and Information Engineering, No. 1, Sec. 4, Roosevelt Rd., Da-an District, 10617, Taipei, Taiwan;National Taiwan University, Department of Computer Science and Information Engineering & Department of Finance, Taipei, Taiwan

  • Venue:
  • Theory of Computing Systems
  • Year:
  • 2011

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Abstract

Consider the following model on the spreading of messages. A message initially convinces a set of vertices, called the seeds, of the Erdős-Rényi random graph G(n,p). Whenever more than a ρ∈(0,1) fraction of a vertex v’s neighbors are convinced of the message, v will be convinced. The spreading proceeds asynchronously until no more vertices can be convinced. This paper derives lower bounds on the minimum number of initial seeds, $\mathrm{min\hbox{-}seed}(n,p,\delta,\rho)$, needed to convince a δ∈{1/n,…,n/n} fraction of vertices at the end. In particular, we show that (1) there is a constant β0 such that $\mathrm{min\hbox{-}seed}(n,p,\delta,\rho)=\Omega(\min\{\delta,\rho\}n)$ with probability 1−n −Ω(1) for p≥β (ln (e/min {δ,ρ}))/(ρ n) and (2) $\mathrm{min\hbox{-}seed}(n,p,\delta,1/2)=\Omega(\delta n/\ln(e/\delta))$ with probability 1−exp (−Ω(δ n))−n −Ω(1) for all p∈[ 0,1 ]. The hidden constants in the Ω notations are independent of p.