Spatial CLT for the supercritical Ornstein-Uhlenbeck superprocess

Abstract

In this paper we consider a superprocess being a measure-valued diffusion corresponding to the equation $u_{t}=Lu+\alpha u-\beta u^{2}$, where $L$ is the infinitesimal operator of the \emph{Ornstein-Uhlenbeck process} and $\beta>0,\:\alpha>0$. The latter condition implies that the process is \emph{supercritical,} i.e. its total mass grows exponentially. This system is known to fulfill a law of large numbers. In the paper we prove the corresponding \emph{central limit theorem}. The limit and the CLT normalization fall into three qualitatively different classes. In what we call the small growth rate case the situation resembles the classical CLT. The weak limit is Gaussian and the normalization is the square root of the size of the system. In the critical case the limit is still Gaussian, however the normalization requires an additional term. Finally, when the growth rate is large the situation is completely different. The limit is no longer Gaussian, the normalization is substantially larger than the classical one and the convergence holds in probability. These different regimes arise as a result of "competition" between spatial smoothing due to the particles' movement and the system's growth which is local.