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  • Open Access

Probing hydrodynamic crossovers with dissipation-assisted operator evolution

N. S. Srivatsa1,2,3,*, Oliver Lunt1,4,*, Tibor Rakovszky5,6, and Curt von Keyserlingk1

  • *These authors contributed equally to this work.
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Phys. Rev. B 113, 165150 – Published 27 April, 2026

DOI: https://doi.org/10.1103/gz9n-v8ty

Abstract

Using artificial dissipation to tame entanglement growth, we chart the emergence of diffusion in a generic interacting lattice model for varying U(1) charge densities. We follow the crossover from ballistic to diffusive transport above a scale set by the scattering length, finding the intuitive result that the diffusion constant scales as D∝1/ρ at low densities ρ. Our numerical approach generalizes the Dissipation-Assisted Operator Evolution algorithm: in the spirit of the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy, we effectively approximate nonlocal operators by their ensemble averages, rather than discarding them entirely. This greatly reduces the operator entanglement entropy, while still giving accurate predictions for diffusion constants across all density scales. We further construct a minimal model for the transport crossover, yielding charge correlation functions which agree well with our numerical data. Our results clarify the dominant contributions to hydrodynamic correlation functions of conserved densities, and serve as a guide for generalizations to low-temperature transport.

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Phys. Rev. B 113, 165150– Published 27 April, 2026
  • Received 13 September 2024
  • Revised 27 November 2025
  • Accepted 6 April 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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