Hydrodynamics without averaging – A hard rods study, by Friedrich Hübner

SciPost Physics Home Authoring Refereeing Submit a manuscript About Hydrodynamics without averaging – A hard rods study Friedrich Hübner SciPost Phys. 20, 081 (2026) · published 11 March 2026 doi: 10.21468/SciPostPhys.20.3.081 pdf BiBTeX RIS Submissions/Reports Abstract On the example of the integrable hard rods model we study the quality of the (generalized) hydrodynamic approximation on a single coarse-grained sample. This is opposed to the traditional approach which averages over an appropriate local equilibrium state. While mathematically more ambiguous, a major advantage of the new approach is that it allows us to disentangle intrinsic diffusion from 'diffusion from convection' effects. For the hard rods we find intrinsic diffusion is absent, which agrees with and clarifies recent findings. Interestingly, the results also apply to not locally thermal states, demonstrating that hydrodynamics (in this model) does not require the assumption of local equilibrium. × TY - JOURPB - SciPost FoundationDO - 10.21468/SciPostPhys.20.3.081TI - Hydrodynamics without averaging – A hard rods studyPY - 2026/03/11UR - https://scipost.org/SciPostPhys.20.3.081JF - SciPost PhysicsJA - SciPost Phys.VL - 20IS - 3SP - 081A1 - Hübner, FriedrichAB - On the example of the integrable hard rods model we study the quality of the (generalized) hydrodynamic approximation on a single coarse-grained sample. This is opposed to the traditional approach which averages over an appropriate local equilibrium state. While mathematically more ambiguous, a major advantage of the new approach is that it allows us to disentangle intrinsic diffusion from 'diffusion from convection' effects. For the hard rods we find intrinsic diffusion is absent, which agrees with and clarifies recent findings. Interestingly, the results also apply to not locally thermal states, demonstrating that hydrodynamics (in this model) does not require the assumption of local equilibrium.ER - × @Article{10.21468/SciPostPhys.20.3.081, title={{Hydrodynamics without averaging – A hard rods study}}, author={Friedrich Hübner}, journal={SciPost Phys.}, volume={20}, pages={081}, year={2026}, publisher={SciPost}, doi={10.21468/SciPostPhys.20.3.081}, url={https://scipost.org/10.21468/SciPostPhys.20.3.081},} Ontology / Topics See full Ontology or Topics database. Diffusion Euler hydrodynamics Exactly solvable models Generalized hydrodynamics (GHD) Hydrodynamics Integrability/integrable models One-dimensional systems Out-of-equilibrium systems Spatially inhomogeneous systems Author / Affiliation: mappings to Contributors and Organizations See all Organizations. 1 Friedrich Hübner 1 King's College London [KCL] Funder for the research work leading to this publication King's College London