Tue, 10 Jun 2014

14:30 - 15:30
L6

The phase transition in bounded-size Achlioptas processes

Lutz Warnke
(University of Cambridge (DPMS))
Abstract

In the Erdös-Rényi random graph process, starting from an empty graph, in each step a new random edge is added to the evolving graph. One of its most interesting features is the `percolation phase transition': as the ratio of the number of edges to vertices increases past a certain critical density, the global structure changes radically, from only small components to a single giant component plus small ones.


In this talk we consider Achlioptas processes, which have become a key example for random graph processes with dependencies between the edges. Starting from an empty graph these proceed as follows: in each step two potential edges are chosen uniformly at random, and using some rule one of them is selected and added to the evolving graph. We discuss why, for a large class of rules, the percolation phase transition is qualitatively comparable to the classical Erdös-Rényi process.


Based on joint work with Oliver Riordan.

Mon, 14 May 2007
14:15
DH 3rd floor SR

The diameter of G (n,c/n)

Dr Oliver Riordan
(University of Cambridge (DPMS))
Abstract
  Recently, comparison with branching processes has been used to determine the asymptotic behaviour of the diameter (largest graph distance between two points that are in the same component) of various sparse random graph models, giving results for $G(n,c/n)$ as special cases. In ongoing work with Nick Wormald, we have studied $G(n,c/n)$ directly, obtaining much stronger results for this simpler model.  
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