Paper detail

Urns with simultaneous drawing

In classical urn models, one usually draws one ball with replacement at each time unit and then adds one ball of the same colour. Given a weight sequence $(w_k)_{k\in\N}$, the probability of drawing a ball of a certain colour is proportional to $w_k$ where $k$ is the number of balls of this colour. A classical result states that an urn fixates on one colour after a finite time if an only if $\sum_{0}^\infty w_k^{-1} < \infty$. In this paper we shall study the case when at each time unit we draw with replacement a number $d\in\N$ of balls and then add $d$ new balls of matching colours. The main goal is to prove that the result in the case of maximal interaction generalizes assuming in addition that $(w_k)_{k\in\N}$ is non-decreasing.