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JOURNALS // Diskretnaya Matematika // Archive

Diskr. Mat., 2025 Volume 37, Issue 4, Pages 102–117 (Mi dm1872)

A note on the size of the trees in the Galton-Watson forest

Yu. L. Pavlov

Karelian Research Centre of the Russian Academy of Sciences, Petrozavodsk

Abstract: Galton-Watson forests formed by a critical branching process starting with $N$ particles are considered. The total number of descendants of the initial particles is equal to $n$ untill extinction. The number of offspring of each particle has the distribution
\begin{equation*}p_k=\frac{h(k+1)}{(k+1)^\tau}, \quad k=0,1,2, \dots, \quad \tau\in (2,3),\end{equation*}
where $h(x)$ is a slowly varying at infinity function such that $h(x)\rightarrow D, 0<D<\infty,$ as $x\rightarrow \infty$. The limit theorems on the number of trees of a given size and on the maximum size of a tree are proved as $N,n\rightarrow \infty$ in such a way that $n/N \rightarrow \infty$ and $n/N^{\tau-1} \rightarrow 0$.

Keywords: Galton-Watson forest, tree size, limit theorems.

UDC: 519.212.2+519.179.4

Received: 12.03.2025

DOI: 10.4213/dm1872



© Steklov Math. Inst. of RAS, 2026