Adiabatic hydrodynamization with transverse spatial gradients in boost-invariant plasmas
Abstract
The quantitative success of relativistic viscous hydrodynamics in describing the short-lived quark--gluon plasma raises a fundamental question: how does far-from-equilibrium QCD matter approach hydrodynamic behavior so rapidly? Microscopic kinetic-theory studies have related this onset to attractor dynamics, but typically assume transverse homogeneity. We relax this assumption by introducing gradient modes with finite transverse wave number k, extending the analysis of arXiv:2212.00820. These couple different spherical harmonics of the momentum distribution, and the resulting dynamics is controlled by the competition among the expansion rate 1/τ, the collision rate 1/τR, and the gradient scale k. At early times, longitudinal expansion suppresses this coupling, and different spherical harmonic sectors follow their homogeneous attractors. We find that, at later times and sufficiently small k, this gradient coupling drives the system toward a global attractor manifold spanned by hydrodynamic sound and shear modes, on a timescale τD that depends on both the azimuthal harmonic m and kτR. For sufficiently large kτR, the spectral gap closes: perturbations retain finite damping rates and therefore equilibrate, but no longer follow an isolated hydrodynamic attractor or admit a reduced description involving only a few hydrodynamic modes.
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BibTeX
@misc{sharell2026adiabatic,
title = {{Adiabatic hydrodynamization with transverse spatial gradients in boost-invariant plasmas}},
author = {Uri Sharell and Jasmine Brewer and Weiyao Ke},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.20705},
eprint = {2609.20705},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.20705},
}
RIS
TY - UNPB
TI - Adiabatic hydrodynamization with transverse spatial gradients in boost-invariant plasmas
AU - Uri Sharell
AU - Jasmine Brewer
AU - Weiyao Ke
PY - 2026
DA - 2026/09/17
PB - arXiv
DO - 10.48550/arxiv.2609.20705
UR - https://arxiv.org/abs/2609.20705
AB - The quantitative success of relativistic viscous hydrodynamics in describing the short-lived quark--gluon plasma raises a fundamental question: how does far-from-equilibrium QCD matter approach hydrodynamic behavior so rapidly? Microscopic kinetic-theory studies have related this onset to attractor dynamics, but typically assume transverse homogeneity. We relax this assumption by introducing gradient modes with finite transverse wave number k, extending the analysis of arXiv:2212.00820. These couple different spherical harmonics of the momentum distribution, and the resulting dynamics is controlled by the competition among the expansion rate 1/τ, the collision rate 1/τ_R, and the gradient scale k. At early times, longitudinal expansion suppresses this coupling, and different spherical harmonic sectors follow their homogeneous attractors. We find that, at later times and sufficiently small k, this gradient coupling drives the system toward a global attractor manifold spanned by hydrodynamic sound and shear modes, on a timescale τ_D that depends on both the azimuthal harmonic m and kτ_R. For sufficiently large kτ_R, the spectral gap closes: perturbations retain finite damping rates and therefore equilibrate, but no longer follow an isolated hydrodynamic attractor or admit a reduced description involving only a few hydrodynamic modes.
ER -