  Consider the following forest-fire process on a connected graph. Each site of
the graph can be either occupied or vacant. A vacant site becomes occupied with
rate 1. A site is ignited with rate lambda, and its whole occupied cluster
burns instantaneously. The purpose of this paper is to show the existence of a
stationary distribution for forest-fire processes on Z^d, for d >= 2. We define
a distribution as a limit of a sequence of invariant distributions of finite
volume forest-fire processes, and then show it is a stationary distribution for
forest-fire processes on Z^d, d>=2.
