Local limit theorems for random isometries of the plane

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Hauptverfasser: Drogin, Reuben, Hernández, Felipe
Format: Preprint
Veröffentlicht: 2026
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author Drogin, Reuben
Hernández, Felipe
author_facet Drogin, Reuben
Hernández, Felipe
contents We consider a random walk $(Y_N)_{N\geq 0}$ on $\mathbb{R}^2$ generated by successively applying independent random isometries, drawn from a fixed measure $μ$, to the point $0$. When the support of $μ$ is finite and includes an irrational rotation satisfying a Diophantine condition, we establish a local central limit theorem (LCLT) for $Y_N$ down to super-polynomially small scales. When $μ$ includes rotations satisfying a further algebraic condition, we prove that a LCLT holds down to the scale $\exp(-cN^{1/3}/(\log N)^2)$. Due to group-theoretic obstructions, this is sharp for symmetric $μ$, up to the $\log$ factor. Lastly for a special class of asymmetric $μ$, we obtain an LCLT down to the much finer scale $\exp(-cN^{1/2})$. The proofs relate the fine-scale distribution of $Y_N$ to a question about the values of integer polynomials on the unit circle.
format Preprint
id arxiv_https___arxiv_org_abs_2601_16295
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Local limit theorems for random isometries of the plane
Drogin, Reuben
Hernández, Felipe
Probability
Group Theory
Number Theory
We consider a random walk $(Y_N)_{N\geq 0}$ on $\mathbb{R}^2$ generated by successively applying independent random isometries, drawn from a fixed measure $μ$, to the point $0$. When the support of $μ$ is finite and includes an irrational rotation satisfying a Diophantine condition, we establish a local central limit theorem (LCLT) for $Y_N$ down to super-polynomially small scales. When $μ$ includes rotations satisfying a further algebraic condition, we prove that a LCLT holds down to the scale $\exp(-cN^{1/3}/(\log N)^2)$. Due to group-theoretic obstructions, this is sharp for symmetric $μ$, up to the $\log$ factor. Lastly for a special class of asymmetric $μ$, we obtain an LCLT down to the much finer scale $\exp(-cN^{1/2})$. The proofs relate the fine-scale distribution of $Y_N$ to a question about the values of integer polynomials on the unit circle.
title Local limit theorems for random isometries of the plane
topic Probability
Group Theory
Number Theory
url https://arxiv.org/abs/2601.16295