Longest increasing subsequences for distributions with atoms, and an inhomogeneous Hammersley process

Fuente: arXiv
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Autori principali: Basdevant, Anne-Laure, Gerin, Lucas, Marivain, Maxime
Natura: Preprint
Pubblicazione: 2025
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author Basdevant, Anne-Laure
Gerin, Lucas
Marivain, Maxime
author_facet Basdevant, Anne-Laure
Gerin, Lucas
Marivain, Maxime
contents A famous result by Hammersley and Versik-Kerov states that the length $L_n$ of the longest increasing subsequence among $n$ iid continuous random variables grows like $2\sqrt{n}$. We investigate here the asymptotic behavior of $L_n$ for distributions with atoms. For purely discrete random variables, we characterize the asymptotic order of $L_n$ through a variational problem and provide explicit estimates for classical distributions. The proofs rely on a coupling with an inhomogeneous version of the discrete-time continuous-space Hammersley process. This reveals that, in contrast to the continuous case, the discrete setting exhibits a wide range of growth rates between $\mathcal{O}(1)$ and $o(\sqrt{n})$, depending on the tail behavior of the distribution. We can then easily deduce the asymptotics of $L_n$ for a completely arbitrary distribution.
format Preprint
id arxiv_https___arxiv_org_abs_2507_05775
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Longest increasing subsequences for distributions with atoms, and an inhomogeneous Hammersley process
Basdevant, Anne-Laure
Gerin, Lucas
Marivain, Maxime
Combinatorics
Probability
A famous result by Hammersley and Versik-Kerov states that the length $L_n$ of the longest increasing subsequence among $n$ iid continuous random variables grows like $2\sqrt{n}$. We investigate here the asymptotic behavior of $L_n$ for distributions with atoms. For purely discrete random variables, we characterize the asymptotic order of $L_n$ through a variational problem and provide explicit estimates for classical distributions. The proofs rely on a coupling with an inhomogeneous version of the discrete-time continuous-space Hammersley process. This reveals that, in contrast to the continuous case, the discrete setting exhibits a wide range of growth rates between $\mathcal{O}(1)$ and $o(\sqrt{n})$, depending on the tail behavior of the distribution. We can then easily deduce the asymptotics of $L_n$ for a completely arbitrary distribution.
title Longest increasing subsequences for distributions with atoms, and an inhomogeneous Hammersley process
topic Combinatorics
Probability
url https://arxiv.org/abs/2507.05775