Speaker
Description
Hydrodynamics in open quantum systems has recently been proposed to admit a new interpretation: hydrodynamic modes can be viewed as Goldstone modes associated with strong-to-weak spontaneous symmetry breaking (SWSSB) [1]. However, an important conceptual gap remains. SWSSB is defined using nonlinear, information-theoretic diagnostics of mixed states, whereas hydrodynamics is observed through linear response and equal-time correlation functions. In particular, a nontrivial static charge structure factor was identified in Ref. [1] as an additional ingredient linking SWSSB to hydrodynamics, but this point has often been obscured in subsequent discussions. In this talk, I will clarify this connection. I will show how SWSSB constrains the static structure factor, thereby identifying a necessary bridge between nonlinear mixed-state order and physically observable hydrodynamic behavior [2]. I will then present a hydrodynamic Nambu-Goldstone theorem [3] for charge-conserving Lindbladians, showing under what conditions conserved charges in open quantum dynamics necessarily give rise to long-lived hydrodynamic modes. Together, these results provide a sharper framework for understanding when and how hydrodynamics emerges in open quantum systems.
[1] O Ogunnaike, J Feldmeier, JY Lee, PRL 131, 220403 (2023)
[2] JY Lee, arXiv:2605.05288
[3] JY Lee, ongoing work (2026)