Paper detail

Interacting Urn Models

The aim of this paper is to study the asymptotic behavior of strongly reinforced interacting urns with partial memory sharing. The reinforcement mechanism considered is as follows: draw at each step and for each urn a white or black ball from either all the urns combined (with probability $p$) or the urn alone (with probability $1-p$) and add a new ball of the same color to this urn. The probability of drawing a ball of a certain color is proportional to $w_k$ where $k$ is the number of balls of this color. The higher the $p$, the more memory is shared between the urns. The main results can be informally stated as follows: in the exponential case $w_k=ρ^k$, if $p\geq 1/2$ then all the urns draw the same color after a finite time, and if $p<1/2$ then some urns fixate on a unique color and others keep drawing both black and white balls.