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October 1998 The standard additive coalescent
David Aldous, Jim Pitman
Ann. Probab. 26(4): 1703-1726 (October 1998). DOI: 10.1214/aop/1022855879


Regard an element of the set $$\Delta := {(x_1, x_2, \dots): x_1 \geq x_2 \geq \dots \geq 0, \Sigma_i x_i = 1}$$ as a fragmentation of unit mass into clusters of masses $x_i$. The additive coalescent of Evans and Pitman is the $\Delta$-valued Markov process in which pairs of clusters of masses ${x_i, x_j}$ merge into a cluster of mass $x_i + x_j$ at rate $x_i + x_j$. They showed that a version $(\rm X^{\infty}(t), -\infty < t < \infty)$ of this process arises as a $n \to \infty$ weak limit of the process started at time $-1/2 \log n$ with $n$ clusters of mass $1/n$. We show this standard additive coalescent may be constructed from the continuum random tree of Aldous by Poisson splitting along the skeleton of the tree. We describe the distribution of $\rm X^{\infty}(t)$ on $\Delta$ at a fixed time $t$. We show that the size of the cluster containing a given atom, as a process in $t$, has a simple representation in terms of the stable subordinator of index 1/2. As $t \to -\infty$, we establish a Gaussian limit for (centered and normalized) cluster sizes and study the size of the largest cluster.


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David Aldous. Jim Pitman. "The standard additive coalescent." Ann. Probab. 26 (4) 1703 - 1726, October 1998.


Published: October 1998
First available in Project Euclid: 31 May 2002

zbMATH: 0936.60064
MathSciNet: MR1675063
Digital Object Identifier: 10.1214/aop/1022855879

Primary: 60J25
Secondary: 60C05 , 60J65

Keywords: Brownian excursion , Continuum random tree , Random forest , splitting , stable subordinator , Stochastic coalescence , stochastic fragmentation

Rights: Copyright © 1998 Institute of Mathematical Statistics

Vol.26 • No. 4 • October 1998
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