The Annals of Probability

Spines, skeletons and the strong law of large numbers for superdiffusions

Maren Eckhoff, Andreas E. Kyprianou, and Matthias Winkel

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Consider a supercritical superdiffusion $(X_{t})_{t\ge0}$ on a domain $D\subseteq\mathbb{R}^{d}$ with branching mechanism

\[(x,z)\mapsto-\beta(x)z+\alpha(x)z^{2}+\int_{(0,\infty)}(e^{-zy}-1+zy)\Pi(x,dy).\] The skeleton decomposition provides a pathwise description of the process in terms of immigration along a branching particle diffusion. We use this decomposition to derive the strong law of large numbers (SLLN) for a wide class of superdiffusions from the corresponding result for branching particle diffusions. That is, we show that for suitable test functions $f$ and starting measures $\mu$,

\[\frac{\langle f,X_{t}\rangle}{P_{\mu}[\langle f,X_{t}\rangle]}\to W_{\infty}\qquad P_{\mu}\mbox{-}\mathrm{almost}\ \mathrm{surely}\ \mathrm{as}\ t\to\infty,\] where $W_{\infty}$ is a finite, non-deterministic random variable characterized as a martingale limit. Our method is based on skeleton and spine techniques and offers structural insights into the driving force behind the SLLN for superdiffusions. The result covers many of the key examples of interest and, in particular, proves a conjecture by Fleischmann and Swart [Stochastic Process. Appl. 106 (2003) 141–165] for the super-Wright–Fisher diffusion.

Article information

Ann. Probab., Volume 43, Number 5 (2015), 2545-2610.

Received: September 2013
Revised: May 2014
First available in Project Euclid: 9 September 2015

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Mathematical Reviews number (MathSciNet)

Zentralblatt MATH identifier

Primary: 60J68: Superprocesses
Secondary: 60J80: Branching processes (Galton-Watson, birth-and-death, etc.) 60F15: Strong theorems

Superdiffusion measure-valued diffusion skeleton decomposition spine decomposition strong law of large numbers additive and multiplicative martingales almost sure limit theorem


Eckhoff, Maren; Kyprianou, Andreas E.; Winkel, Matthias. Spines, skeletons and the strong law of large numbers for superdiffusions. Ann. Probab. 43 (2015), no. 5, 2545--2610. doi:10.1214/14-AOP944.

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