Orateur
Description
Hydrodynamics is expected to govern the universal long-time and large-scale dynamics of interacting systems. However, its applicability to intrinsically non-equilibrium states with topological defects remains poorly understood. Superfluids containing vortices provide a paradigmatic example: such configurations exhibit singular phase structures, strong spatial inhomogeneities, and additional gapped degrees of freedom, all of which lie outside the standard hydrodynamic paradigm. Whether a controlled hydrodynamic description survives under these conditions is a priori unclear. In this work, we show that a predictive hydrodynamic framework can nevertheless be constructed for superfluids containing vortices. In the presence of a finite vortex density, the superfluid velocity is no longer conserved but instead relaxes over time, with a rate controlled by the density of vortices. This provides the key macroscopic input that encodes vortex-induced dissipation and leads to a closed set of effective equations governing the long-wavelength dynamics. We analyze the resulting collective excitations and show that the system exhibits collective modes that originate from the hydrodynamic sector but become time dependent and gapped due to vortex-induced relaxation, leading to deviations from conventional superfluid hydrodynamics, including modified dispersion relations and attenuation. Crucially, the system under consideration admits no stationary background, rendering standard linear response and quasi-normal mode analyses inapplicable. To overcome this, we perform fully nonlinear real-time evolution in a holographic superfluid model with vortex configurations and directly probe the emergent macroscopic dynamics. We find that the late-time evolution is quantitatively captured by the effective hydrodynamic description, providing nontrivial evidence that hydrodynamics can persist far beyond its traditional regime of validity. Our results establish a concrete framework for incorporating vortex-induced relaxation into superfluid hydrodynamics and offer a new perspective on non-equilibrium dynamics in strongly coupled systems with topological defects.
