## The extremal process of two-speed branching Brownian motion.(English)Zbl 1288.60108

Authors’ abstract: We construct and describe the extremal process for variable speed branching Brownian motion, studied recently by M. Fang and O. Zeitouni [J. Stat. Phys. 149, No. 1, 1–9 (2012; Zbl 1259.82141)], for the case of piecewise constant speeds; in fact, for simplicity we concentrate on the case when the speed is $$\sigma_1$$ for $$s\leq bt$$ and $$\sigma_2$$ when $$bt\leq s\leq t$$. In the case $$\sigma_1>\sigma_2$$, the process is the concatenation of two BBM extremal processes, as expected. In the case $$\sigma_1<\sigma_2$$, a new family of cluster point processes arises, that are similar, but distinctively different from the BBM process. Our proofs follow the strategy of L.-P. Arguin et al. [Probab. Theory Relat. Fields 157, No. 3–4, 535–574 (2013; Zbl 1286.60045)].

### MSC:

 60J80 Branching processes (Galton-Watson, birth-and-death, etc.) 60J70 Applications of Brownian motions and diffusion theory (population genetics, absorption problems, etc.) 82B44 Disordered systems (random Ising models, random Schrödinger operators, etc.) in equilibrium statistical mechanics

### Citations:

Zbl 1259.82141; Zbl 1286.60045
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