Strength in numbers? Not always!

We propose a simple model to compute the probability of success under a quorum sensing strategy. We show that a quorum sensing strategy has a higher probability of success than an individualistic strategy when, for instance, the probability of success for a single individual is low and the cost of building a quorum is not too high. On the other hand if the cost of building a quorum is too high then the probability of success under quorum sensing always decreases as a function of the quorum

Survival and coexistence for a multitype contact process

We study the ergodic theory of a multitype contact process with equal death rates and unequal birth rates on the $d$-dimensional integer lattice and regular trees. We prove that for birth rates in a certain interval there is coexistence on the tree, which by a result of Neuhauser is not possible on the lattice. We also prove a complete convergence result when the larger birth rate falls outside of this interval.Comment: Published in at http://dx.doi.org/10.1214/08-AOP422 the Annals of Probability (http://www.imstat.org/aop/) by the Institute of Mathematical Statistics (http://www.imstat.org