Article,

Branching processes in Lévy processes: the exploration process

, and .
Ann. Probab., 26 (1): 213--252 (1998)

Abstract

It has been known for a long time that there exist fundamental connections between branching trees and random walks (or processes with stationary independent increments). Early papers are due to Harris (1952), D. G. Kendall (1951), Dwass (1969) and Lamperti (1967) (they are cited in the paper). The present paper by Le Gall and Le Jan is a further important step to a deeper understanding of this connection. The basic notions are the exploration process of a Galton-Watson tree and the height process of a Lévy process. The exploration process at time $n$ is the generation of the individual in the tree visited at time $n$, assuming that the individuals are visited successively to the law of primogeniture. This process is in itself complicated, but it can be constructed as a functional of a suitable left-continuous random walk. Conversely, the authors construct the height process of a spectrally positive Lévy process, which can be understood as the exploration process of a general continuous branching process. This construction has important applications. In particular, it allows an adequate formulation of the classical Ray-Knight theorem for such Lévy processes. For related results see a paper by J. Geiger in Stochastic partial differential equations (Edinburgh, 1994), 72--96, Cambridge Univ. Press, Cambridge, 1995; MR1352736 (96f:60146).

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