Hierarchical Lorentz Mirror Model: Normal Transport and a Universal $2/3$ Mean--Variance Law

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Auteurs principaux: Lefevere, Raphael, Tasaki, Hal
Format: Preprint
Publié: 2026
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author Lefevere, Raphael
Tasaki, Hal
author_facet Lefevere, Raphael
Tasaki, Hal
contents The Lorentz mirror model provides a clean setting to study macroscopic transport generated solely by quenched environmental randomness. We introduce a hierarchical version whose distribution of left--right crossings satisfies an exact recursion. In dimensions $d\geq 3$, we prove normal transport: the mean conductance scales as (cross-section)/(length) on all length scales. A Gaussian closure, supported by numerics, predicts that the variance-to-mean ratio of the conductance converges to the universal value $2/3$ for all $d\geq 2$ (the ``$2/3$ law''). We provide numerical evidence for the $2/3$ law in the original (non-hierarchical) Lorentz mirror model in $d=3$, and conjecture that it is a universal signature of normal transport induced by random current matching. In the marginal case $d=2$, our hierarchical recursion reproduces the known scaling of the mean conductance and its variance. A YouTube video discussing the background and the main results of the paper is available: https://youtu.be/G1nqKd6MiXo
format Preprint
id arxiv_https___arxiv_org_abs_2602_07988
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Hierarchical Lorentz Mirror Model: Normal Transport and a Universal $2/3$ Mean--Variance Law
Lefevere, Raphael
Tasaki, Hal
Statistical Mechanics
Mathematical Physics
Probability
The Lorentz mirror model provides a clean setting to study macroscopic transport generated solely by quenched environmental randomness. We introduce a hierarchical version whose distribution of left--right crossings satisfies an exact recursion. In dimensions $d\geq 3$, we prove normal transport: the mean conductance scales as (cross-section)/(length) on all length scales. A Gaussian closure, supported by numerics, predicts that the variance-to-mean ratio of the conductance converges to the universal value $2/3$ for all $d\geq 2$ (the ``$2/3$ law''). We provide numerical evidence for the $2/3$ law in the original (non-hierarchical) Lorentz mirror model in $d=3$, and conjecture that it is a universal signature of normal transport induced by random current matching. In the marginal case $d=2$, our hierarchical recursion reproduces the known scaling of the mean conductance and its variance. A YouTube video discussing the background and the main results of the paper is available: https://youtu.be/G1nqKd6MiXo
title Hierarchical Lorentz Mirror Model: Normal Transport and a Universal $2/3$ Mean--Variance Law
topic Statistical Mechanics
Mathematical Physics
Probability
url https://arxiv.org/abs/2602.07988