2025/04/24 by G. M. Sampaio, Sampaio, G. M., Gabriel Rabelo-Soares +3 · 1 citation
Earth and Planetary Sciences · Engineering · Physics and Astronomy · #FOS: Physical sciences #Fluid Dynamics and Turbulent Flows #General Relativity and Quantum Cosmology (gr-qc) #Geophysics and Gravity Measurements #High Energy Physics - Phenomenology (hep-ph) #High Energy Physics - Theory (hep-th) #Nuclear Theory (nucl-th) #Quantum chaos and dynamical systems
paper · pdf · doi:10.48550/arxiv.2504.17152
openalex publication_date 2025/04/24 · openalex created_date 2025/10/18 · openalex updated_date 2026/07/28
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.