Extremal-process moderate-deviation conjecture for branching random walks

Assume the branching random walk satisfies the supercriticality, boundary-case, Gaussianity, and peeling-lemma assumptions, and is non-lattice. Let ϕ ⁣:RR\phi\colon\mathbb{R}\to\mathbb{R} be continuous with compact support, and let (xn)(x_n) satisfy

xn,xn=O(n)x_n\to\infty,\qquad x_n=O(\sqrt{n})

as nn\to\infty. Write mnm_n for the centering sequence, let V(u)V(u) denote the position of an individual uu at generation nn, and let σ\sigma be the variance parameter. Define

CNL(ϕ)=1σ32πlim0yeyE\originalleft[1eu=ϕ(V(u)y)\aftergroup\originalright]dy.C_{\mathrm{NL}}(\phi)=\frac{1}{\sigma^3}\sqrt{\frac{2}{\pi}}\lim_{\ell\to\infty}\int_0^\infty y\mathrm{e}^{y}\,\mathbb{E}\mathopen{}\mathclose\bgroup\originalleft[1-\mathrm{e}^{-\sum_{|u|=\ell}\phi(V(u)-y)}\aftergroup\egroup\originalright]\,\mathrm{d}y.

Extremal-process moderate-deviation conjecture. As nn\to\infty,

E\originalleft[1eu=nϕ(V(u)mnxn)\aftergroup\originalright]CNL(ϕ,a)xnexnxn2/(2nσ2).\mathbb{E}\mathopen{}\mathclose\bgroup\originalleft[1-\mathrm{e}^{-\sum_{|u|=n}\phi(V(u)-m_n-x_n)}\aftergroup\egroup\originalright]\sim C_{\mathrm{NL}}(\phi,a)x_n\mathrm{e}^{-x_n-x_n^2/(2n\sigma^2)}.

This extends the upper moderate-deviation asymptotic for the maximum to Laplace functionals of the branching random walk viewed from its extremal position, thereby connecting moderate deviations with the limiting extremal process. The supplied statement is presented as a conjecture, but its resolution is not specified in the source material.

Sources & referencesView supporting material

Primary source

Louis Chataignier and Lianghui Luo, “Upper moderate deviation probabilities for the maximum of a branching random walk”, arXiv:2601.08766 (2026).

Additional references

2 papers in this index state this conjecture (2022–2026). The statement above is taken from the most recent of them; the others are arXiv:2202.01584.

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