A functional central limit theorem for branching random walks, almost sure weak convergence and applications to random trees

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Authors

  • Rudolf Grübel
  • Zakhar Kabluchko

External Research Organisations

  • University of Münster
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Details

Original languageEnglish
Pages (from-to)3659-3698
Number of pages40
JournalAnnals of Applied Probability
Volume26
Issue number6
Publication statusPublished - Dec 2016

Abstract

Let W∞(β) be the limit of the Biggins martingale Wn(β) associated to a supercritical branching random walk with mean number of offspring m. We prove a functional central limit theorem stating that as n→∞the process {equation presented} converges weakly, on a suitable space of analytic functions, to a Gaussian random analytic function with random variance. Using this result, we prove central limit theorems for the total path length of random trees. In the setting of binary search trees, we recover a recent result of R. Neininger [Random Structures Algorithms 46 (2015) 346-361], but we also prove a similar theorem for uniform random recursive trees. Moreover, we replace weak convergence in Neininger's theorem by the almost sure weak (a.s.w.) convergence of probability transition kernels. In the case of binary search trees, our result states that {equation presented} where EPLn is the external path length of a binary search tree Xn with n vertices, EPL∞ is the limit of the Régnier martingale and L{.|Gn} denotes the conditional distribution w.r.t. the σ-algebra Gn generated by X1, . . . , Xn. Almost sure weak convergence is stronger than weak and even stable convergence. We prove several basic properties of the a.s.w. convergence and study a number of further examples in which the a.s.w. convergence appears naturally. These include the classical central limit theorem for Galton-Watson processes and the Pólya urn.

Keywords

    Almost sure weak convergence, Binary search trees, Branching random walk, Functional central limit theorem, Galton-Watson processes, Gaussian analytic function, Mixing convergence, Pólya urns, Quicksort distribution, Random recursive trees, Stable convergence

ASJC Scopus subject areas

Cite this

A functional central limit theorem for branching random walks, almost sure weak convergence and applications to random trees. / Grübel, Rudolf; Kabluchko, Zakhar.
In: Annals of Applied Probability, Vol. 26, No. 6, 12.2016, p. 3659-3698.

Research output: Contribution to journalArticleResearchpeer review

Grübel R, Kabluchko Z. A functional central limit theorem for branching random walks, almost sure weak convergence and applications to random trees. Annals of Applied Probability. 2016 Dec;26(6):3659-3698. doi: 10.48550/arXiv.1410.0469, 10.1214/16-AAP1188
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abstract = "Let W∞(β) be the limit of the Biggins martingale Wn(β) associated to a supercritical branching random walk with mean number of offspring m. We prove a functional central limit theorem stating that as n→∞the process {equation presented} converges weakly, on a suitable space of analytic functions, to a Gaussian random analytic function with random variance. Using this result, we prove central limit theorems for the total path length of random trees. In the setting of binary search trees, we recover a recent result of R. Neininger [Random Structures Algorithms 46 (2015) 346-361], but we also prove a similar theorem for uniform random recursive trees. Moreover, we replace weak convergence in Neininger's theorem by the almost sure weak (a.s.w.) convergence of probability transition kernels. In the case of binary search trees, our result states that {equation presented} where EPLn is the external path length of a binary search tree Xn with n vertices, EPL∞ is the limit of the R{\'e}gnier martingale and L{.|Gn} denotes the conditional distribution w.r.t. the σ-algebra Gn generated by X1, . . . , Xn. Almost sure weak convergence is stronger than weak and even stable convergence. We prove several basic properties of the a.s.w. convergence and study a number of further examples in which the a.s.w. convergence appears naturally. These include the classical central limit theorem for Galton-Watson processes and the P{\'o}lya urn.",
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T1 - A functional central limit theorem for branching random walks, almost sure weak convergence and applications to random trees

AU - Grübel, Rudolf

AU - Kabluchko, Zakhar

N1 - Publisher Copyright: © Institute of Mathematical Statistics, 2016.

PY - 2016/12

Y1 - 2016/12

N2 - Let W∞(β) be the limit of the Biggins martingale Wn(β) associated to a supercritical branching random walk with mean number of offspring m. We prove a functional central limit theorem stating that as n→∞the process {equation presented} converges weakly, on a suitable space of analytic functions, to a Gaussian random analytic function with random variance. Using this result, we prove central limit theorems for the total path length of random trees. In the setting of binary search trees, we recover a recent result of R. Neininger [Random Structures Algorithms 46 (2015) 346-361], but we also prove a similar theorem for uniform random recursive trees. Moreover, we replace weak convergence in Neininger's theorem by the almost sure weak (a.s.w.) convergence of probability transition kernels. In the case of binary search trees, our result states that {equation presented} where EPLn is the external path length of a binary search tree Xn with n vertices, EPL∞ is the limit of the Régnier martingale and L{.|Gn} denotes the conditional distribution w.r.t. the σ-algebra Gn generated by X1, . . . , Xn. Almost sure weak convergence is stronger than weak and even stable convergence. We prove several basic properties of the a.s.w. convergence and study a number of further examples in which the a.s.w. convergence appears naturally. These include the classical central limit theorem for Galton-Watson processes and the Pólya urn.

AB - Let W∞(β) be the limit of the Biggins martingale Wn(β) associated to a supercritical branching random walk with mean number of offspring m. We prove a functional central limit theorem stating that as n→∞the process {equation presented} converges weakly, on a suitable space of analytic functions, to a Gaussian random analytic function with random variance. Using this result, we prove central limit theorems for the total path length of random trees. In the setting of binary search trees, we recover a recent result of R. Neininger [Random Structures Algorithms 46 (2015) 346-361], but we also prove a similar theorem for uniform random recursive trees. Moreover, we replace weak convergence in Neininger's theorem by the almost sure weak (a.s.w.) convergence of probability transition kernels. In the case of binary search trees, our result states that {equation presented} where EPLn is the external path length of a binary search tree Xn with n vertices, EPL∞ is the limit of the Régnier martingale and L{.|Gn} denotes the conditional distribution w.r.t. the σ-algebra Gn generated by X1, . . . , Xn. Almost sure weak convergence is stronger than weak and even stable convergence. We prove several basic properties of the a.s.w. convergence and study a number of further examples in which the a.s.w. convergence appears naturally. These include the classical central limit theorem for Galton-Watson processes and the Pólya urn.

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