We employ a new method, "gauge cooling", to stabilize complex Langevin simulations of QCD with heavy quarks. The results are checked against results obtained with reweigthing; we find agreement within the estimated errors. The method allows us to go to previously unaccessible high densities.

Nonthermal fixed points of the dynamics of a dilute degenerate Bose gas far from thermal equilibrium are analysed in two and three spatial dimensions. Universal power-law distributions, previously found within a nonperturbative quantum-field theoretical approach and recently shown to be related to vortical dynamics and superfluid turbulence [Phys. Rev. B 84, 020506(R) (2011)], are studied in detail. The results imply an interpretation of the scaling behavior in terms of independent vortex excitations of the superfluid and show that the statistics of topological excitations can be described in the framework of wave turbulence. The particular scaling exponents observed in the single-particle momentum distributions are found to be consistent with irreversibility as well as conservation laws obeyed by the wave interactions. Moreover, long-wavelength acoustic excitations of the vortex-bearing condensate, driven by vortex annihilations, are found to follow a nonthermal power law. Considering vortex correlations in a statistical model, the long-time departure from the nonthermal fixed point is related to vortex-antivortex pairing. The studied nonthermal fixed points are accessible in cold-gas experiments. The results shed light on fundamental aspects of superfluid turbulence and have strong potential implications for related phenomena, e.g., in early-universe inflation or quark-gluon plasma dynamics.

Nonthermal fixed points of far-from-equilibrium dynamics of a dilute degenerate Bose gas are analysed in two and three spatial dimensions. For such systems, universal power-law distributions, previously found within a nonperturbative quantum-field theoretic approach, are shown to be related to vortical dynamics and superfluid turbulence. The results imply an interpretation of the momentum scaling at the nonthermal fixed points in terms of independent vortex excitations of the superfluid. Long-wavelength acoustic excitations on the top of these are found to follow a nonthermal power law. The results shed light on fundamental aspects of superfluid turbulence and have strong potential implications for related phenomena studied, e.g., in early-universe inflation or quark-gluon plasma dynamics. , 67.85.DeFrom the formation of Bose-Einstein condensates in ultracold gases to quark-gluon plasmas produced in heavyion collisions, over a range of twentyfour orders of magnitude in temperature, nonequilibrium dynamics governs many interesting phenomena. Turbulence is an outstanding and intricate example, which can be described as an oriented stationary flow of energy or particles between different scales. This idea of an energy cascade goes back to the work of Richardson in the context of atmospheric science [1]. Kolmogorov, in his 1941 mathematical discussion of turbulence in an incompressible fluid, added the concept of universality and scaling [2]. More recently, turbulence has been studied in the context of the inflationary early universe as well as of strongly correlated matter produced in heavy-ion collisions [3][4][5][6][7].Dynamical critical phenomena, i.e., fixed points of the evolution away from thermal equilibrium have been proposed. They potentially affect the equilibration process by forcing the evolution to critically slow down before final thermalization. New scaling laws were found by analysing non-perturbative Kadanoff-Baym dynamic equations [4,5]. Analogous predictions for a nonrelativistic Bose gas were given in [6], proposing strong matterwave turbulence in the regime of long-range excitations.Superfluid turbulence, also referred to as quantum turbulence (QT) has been the subject of extensive studies in the context of helium [9]. In contrast to eddies in classical fluids vorticity in a superfluid is quantized [10,11], and the creation and annihilation processes of quantized vortices are distinctly different [9]. The observation of a Kolmogorov 5/3-law [2] in experiments with superfluid helium, cf.[12] for a review, received much attention [13][14][15][16][17][18][19]. In particular, the role of the normal-fluid as compared to the superfluid component in the turbulent flow * Electronic address: t.gasenzer@uni-heidelberg.de is under debate [9]. In the context of the kinetics of condensation and the development of long-range order in a dilute Bose gas, the role of turbulence in the superfluid and its acoustic excitations was discussed in Refs. [20,21], see also [22] for a recent review. A possible observation...