Nonmonotonic Coexistence Regions for the Two-type Richardson Model on Graphs
Journal article, 2006

In the two-type Richardson model on a graph G=(V,E), each vertex is at a given time in state 0,1 or 2. A 0 flips to a 1 (resp. 2) at rate λ1 (λ2) times the number of neighboring 1's (2's), while 1's and 2's never flip. When G is infinite, the main question is whether, starting from a single 1 and a single 2, with positive probability we will see both types of infection reach infinitely many sites. This has previously been studied on the d-dimensional cubic lattice Z2, d≥2, where the conjecture (on which a good deal of progress has been made) is that such coexistence has positive probability if and only if λ1 =λ2. In the present paper examples are given of other graphs where the set of points in the parameter space which admit such coexistence has a more surprising form. In particular, there exist graphs exhibiting coexistence at some value of (λ1 /λ2) and non-coexistence when this ratio is brought closer to 1.

Author

Maria Deijfen

Olle Häggström

University of Gothenburg

Chalmers, Mathematical Sciences, Mathematical Statistics

Electronic Journal of Probability

10836489 (eISSN)

Vol. 11 331-344

Subject Categories

Mathematics

More information

Created

10/6/2017