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Gaussian generally covariant hydrodynamics

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arxiv 2504.17152 v2 pith:3TUQYZ2P submitted 2025-04-24 hep-th gr-qchep-phnucl-th

Gaussian generally covariant hydrodynamics

classification hep-th gr-qchep-phnucl-th
keywords hydrodynamicstheoryapplicabilitycovariantdifferentexpandedgaussiangenerally
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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We develop a version of fluctuating relativistic hydrodynamics in a way very different from the usual derivation: Instead of treating it as a coarse-grained deterministic theory expanded in gradients of equilibrium quantities, we treat it as a stochastic theory, characterized by partition functions in each cells, expanded in cumulants. We show that the Gaussian ansatz allows us, via the gravitational Ward identities acting as a constraint between the variance and the average, to maintain full general covariance, with hydrodynamic flow emerging as an approximate Killing vector. If the symmetry of relativistic hydrodynamics, volume-preserving diffeomorphisms, is preserved, we show that linear response formulae are also generally covariant. We discuss our results and argue that in this approach, the applicability of the effective theory is parametrized around a very different quantity than the Knudsen number, offering hope of understanding the applicability of hydrodynamics to small systems.

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Cited by 4 Pith papers

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

  1. Gaussian non relativistic spontaneously stochastic hydrodynamics

    physics.flu-dyn 2026-07 conditional novelty 6.0

    The paper proposes that non-relativistic incompressible hydrodynamics is the infrared limit of a Gaussian stochastic theory, with compressible-scale counterterms generating spontaneous stochasticity and anomalous dissipation.

  2. Lorentz-Covariant Spectral Bounds from Thermal Quantum Field Theory

    nucl-th 2026-07 reject novelty 6.0

    Boosting a hot quantum fluid spreads a rest-frame relaxation mode into a band of modes; the boosted gap is bounded by Γ_gap/[γ(1+v v_max)] and the gradient-expansion radius is squeezed by the sound speed.

  3. Lorentz-Covariant Spectral Bounds from Thermal Quantum Field Theory: Retarded Green's Functions, Kubo Relations, and Holographic Constraints

    nucl-th 2026-07 conditional novelty 5.0

    The paper derives Lorentz-covariant bounds on boosted-frame non-hydrodynamic relaxation rates from thermal QFT axioms, and shows in a holographic N=4 SYM plasma that relaxation speeds up under boost rather than slowing down.

  4. Gaussian pseudogauge invariant hydrodynamics with spin

    hep-th 2026-04 unverdicted novelty 5.0

    A formulation of fluctuating hydrodynamics with spin is presented that achieves pseudo-gauge invariance and foliation covariance through torsion and second-order gravitational Ward identities.