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  • Open Access

Leading Lyapunov exponent in the glasma

Pooja*, Dana Avramescu†, and Tuomas Lappi‡

  • *Contact author: pooja.p.pooja@jyu.fi
  • †Contact author: dana.d.avramescu@jyu.fi
  • ‡Contact author: tuomas.v.v.lappi@jyu.fi
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Phys. Rev. D 114, 014010 – Published 6 July, 2026

DOI: https://doi.org/10.1103/6j35-n7z4

Abstract

We show that small perturbations in the boost-invariant color fields of the glasma exhibit an exponential growth with the square root of time. We interpret this growth rate as a Lyapunov exponent, related to entropy production and the thermalization timescale in the earliest stage of heavy-ion collisions. Working in a regime that is linear in this perturbation, we extract the time dependence of this mode as ∼exp(0.4g2μτ) for SU(2), where g2μ is proportional to the saturation scale and the square-root dependence is caused by the boost-invariant expansion of the system. We show that the growth rate of this mode is, unlike its amplitude, remarkably insensitive to the details of how the perturbations are initialized. In particular, we show that the unstable mode couples to all momentum scales present in the initial perturbation.

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Phys. Rev. D 114, 014010– Published 6 July, 2026
  • Received 25 February 2026
  • Accepted 12 May 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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