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Convergence of the hydrodynamic gradient expansion in relativistic kinetic theory

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arxiv 2408.14316 v2 pith:K2S5MLMV submitted 2024-08-26 nucl-th astro-ph.HEhep-th

classification nucl-thastro-ph.HEhep-th
keywords convergenceproverelativisticfinitehydrodynamickineticnon-hydrodynamicradius
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abstract

We rigorously prove that, in any relativistic kinetic theory whose non-hydrodynamic sector has a finite gap, the Taylor series of all hydrodynamic dispersion relations has a finite radius of convergence. Furthermore, we prove that, for shear waves, such radius of convergence cannot be smaller than $1/2$ times the gap size. Finally, we prove that the non-hydrodynamic sector is gapped whenever the total scattering cross-section (expressed as a function of the energy) is bounded below by a positive non-zero constant. These results, combined with well-established covariant stability criteria, allow us to derive a rigorous upper bound on the shear viscosity of relativistic dilute gases.

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Cited by 6 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. The Lorentzian geometry of relaxation

    nucl-th 2026-07 accept novelty 8.0 of 10

    Causality forces purely relaxational dispersion relations to follow spacelike trajectories on the Lorentzian {iω,ik} plane, producing universal bounds on diffusivity, viscosity, time-dilation deviations, and hydrodyna...

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    nucl-th 2026-08 accept novelty 7.0 of 10

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  4. Relativistic transport near moving interfaces

    nucl-th 2026-07 accept novelty 7.0 of 10

    Interface-localized linear solutions in relativistic media are superpositions of imaginary-frequency modes selected by intersecting the spectrum with the line iω = v ik.

  5. Dispersion relations of relativistic radiation hydrodynamics

    astro-ph.HE 2024-11 accept novelty 7.0 of 10

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  6. The quasi-normal modes of relativistic Fokker-Planck kinetic theory

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    The quasi-normal spectrum of ultrarelativistic Fokker-Planck kinetic theory consists of an exact diffusive hydrodynamic mode, continuous ballistic bands, and a hydrogenic discrete tower in three dimensions.

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