Majority dynamics on sparse random graphs

Wed Oct 5, 2022 4:15 p.m.—5:15 p.m.
Exterior of Sheffield-Sterling-Strathcona Hall featuring a stone carving of Yale's coat of arms and motto

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Seminar: 
Colloquium

Event time: 
Wednesday, October 5, 2022 - 4:15pm

Location: 
LOM 206

Speaker: 
Jeong Han Kim

Speaker affiliation: 
KIAS

Event description: 
Majority dynamics on a graph G is a deterministic process such that every vertex updates its ±1-assignment according to the majority assignment on its neighbor simultaneously at each step.

Benjamini, Chan, O’Donnell, Tamuz and Tan conjectured that, in the Erd˝os–R´enyi random graph G(n, p), the random initial ±1-assignment converges to a 99%-agreement with high probability whenever p >> 1/n.

This conjecture was first confirmed for p ≥ λn−1/2 for a large constant λ by Fountoulakis, Kang and Makai. Although this result has been reproved recently by Tran and Vu and by Berkowitz and Devlin, it was unknown whether the conjecture holds for p < λn−1/2 .

We break this Ω(n −1/2 )-barrier by proving the conjecture for sparser random graphs G(n, p) with λn  −  2/3 log2/3 n   ≤   p     ≤     λn −  1/2 for a large constant λ > 0. Joint work with D. Chakraborti, J. Lee, & T. Tran, and with L. Tran.