Open Access
2019 Rapid social connectivity
Itai Benjamini, Jonathan Hermon
Electron. J. Probab. 24: 1-33 (2019). DOI: 10.1214/19-EJP294


Given a graph $G=(V,E)$, consider Poisson($|V|$) walkers performing independent lazy simple random walks on $G$ simultaneously, where the initial position of each walker is chosen independently with probability proportional to the degrees. When two walkers visit the same vertex at the same time they are declared to be acquainted. The social connectivity time $\mathrm{SC} (G)$ is defined as the first time in which there is a path of acquaintances between every pair of walkers. It is shown that when the average degree of $G$ is $d$, with high probability \[ c\log |V| \le \mathrm{SC} (G) \le C d^{1+5 \cdot 1_{G \text{ is not regular} } } \log ^3 |V|. \] When $G$ is regular the lower bound is improved to $\mathrm{SC} (G) \ge \log |V| -6 \log \log |V| $, with high probability. We determine $\mathrm{SC} (G)$ up to a constant factor in the cases that $G$ is an expander and when it is the $n$-cycle.


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Itai Benjamini. Jonathan Hermon. "Rapid social connectivity." Electron. J. Probab. 24 1 - 33, 2019.


Received: 28 May 2018; Accepted: 17 March 2019; Published: 2019
First available in Project Euclid: 9 April 2019

zbMATH: 1419.82053
MathSciNet: MR3940762
Digital Object Identifier: 10.1214/19-EJP294

Primary: 05C81 , 60J10 , 60K35 , 82B43 , 82C41 , 91D30

Keywords: Coalescence process , Giant component , Random walks , Social network

Vol.24 • 2019
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