Würzburg Seminar on Quantum Field Theory and Gravity (Sebastian Waeber, 27.10.2026)

The two-fluid model describes a finite-temperature superfluid as an inviscid condensate coexisting with a viscous normal component, coupled through quantized vortices via mutual friction. Existing approaches either rely on empirically calibrated friction coefficients or treat the normal fluid as a passive thermal bath. Recent experiments in He II show that this picture is incomplete: the normal fluid becomes turbulent and non-Gaussian, driven by the superfluid vortices. This talk presents the first real-time simulation of 2D two-fluid turbulence in which the back-reaction of vortices on the normal fluid emerges from the dynamics rather than being modelled. Using the AdS/CFT correspondence, the full Einstein-Maxwell-scalar system is evolved in 3+1 dimensions, with the normal fluid encoded in the dynamical black-hole geometry. By imposing a background superflow above the Landau critical velocity, which continuously creates vortices, a statistically steady turbulent state is sustained. The main results are non-Gaussian, anisotropic normal-fluid velocity statistics and a temperature-induced suppression of normal-fluid fluctuations, despite an increasing vortex density, which happens due to the thermal depletion of the superfluid density.