Universal tracer statistics in single-file transport

Soumyabrata Saha; Jitendra Kethepalli; Benjamin Guiselin; Jacopo De Nardis; Tridib Sadhu

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arXiv · 2604.24741

Universal tracer statistics in single-file transport

Soumyabrata Saha·Jitendra Kethepalli·Benjamin Guiselin·Jacopo De Nardis·Tridib Sadhu

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Abstract

We uncover an emergent universality in the large-scale, long-time statistics of a one-dimensional hard-rod gas evolving under two fundamentally different classes of microscopic dynamics: stochastic (diffusive) and unitary (ballistic). Remarkably, despite the difference of the two systems, the one-time joint distribution of the positions of multiple tracers exhibits identical non-Gaussian fluctuations, up to a simple dynamical scaling. This universality holds in both annealed and quenched ensembles, demonstrating a persistent memory of the initial state. Differences between the dynamics manifest at large scales only in multi-time statistics. Our conclusions are based on explicit large-deviation results for the one-time statistics of tracer pairs and the two-time statistics of a single tracer. Similar physics extends to current fluctuations, demonstrated explicitly in the quenched ensemble. We obtain these results from exact microscopic solutions for both dynamics and, independently, from fluctuating hydrodynamics in the ballistic case in the annealed ensemble. Our rare-event simulations further corroborate these findings and provide a novel demonstration of sampling atypical fluctuations in both types of hard-rod gas.

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Soumyabrata Saha, Jitendra Kethepalli, Benjamin Guiselin, Jacopo De Nardis, Tridib Sadhu. 2026-04-27. Universal tracer statistics in single-file transport. https://arxiv.org/abs/2604.24741

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