On the description of rotational flow in quantum hydrodynamics

B. B. Varga, Shulamith Graus Eckstein

J.R. Barker

We have previously shown that the flow in open quantum dots may be described in terms of meandering open orbits which separate regions of trapped flows around vortices. Furthermore the topology of the flow follows from a simple geometrical construction in which the classical ballistic trajectories are first computed and then all crossings are replaced by hyperbolic flow separation and for which all trapped flows form quantised closed orbits. In the present paper we extend this picture to a computational methodology for developing quantum hydrodynamic descriptions of flows in the presence of quantised vortices by extension from classical hydrodynamics. For coherent transport we again encounter the Bohm quantum potential but the singularity structure is predetermined by applying a fictitious repulsion which prevents trajectories and hence streamlines crossing. This leads to vortex producing terms in the hydrodynamic equations. The discussion is completed by including the effects of non-hermitian potentials into the Hamiltonian in order to simulate dissipation and phase breaking flows.

Novak, Igor

Hydrodynamic phenomena seem to be ubiquitous in the universe. Hydrodynamics provides an effective, long-wavelength description of both classical and quantum systems. We study the universal spatial features of certain non-equilibrium steady states corresponding to flows of strongly correlated fluids over obstacles. We identify spatial collective modes of the strongly coupled many body system. These modes can be both hydrodynamical or non-hydrodynamical. Analytic examples can be found in the large-dimension limit of the bulk theory, but in three dimensions as well. We construct the general first-order hydrodynamic theory invariant under time translations, the Euclidean group of spatial transformations and preserving particle number. Such theories are important in many situations, from hydrodynamics of graphene to flocking behaviour of birds and motion of self-propelled organisms. We apply our non-boost invariant model of hydrodynamics to concrete flow configurations - the Poiseuille, Couette and Taylor-Couette flows. We also test the instability of the Poiseuille flow.

Moise Bonilla–Licea, Dieter Schuch

Y. S. Ciou

The artificial fluid model known as "Schrödinger flow" (SF) can represent rotational flow with dissipative effects, and has attracted attention despite its gap from real-world fluid behavior. To address the structural discrepancy arising from the incomplete transition from quantum hydrodynamics to classical fluid dynamics, we propose a variant of the hydrodynamic Schrödinger equation (HSE) that better aligns with classical formulations. We then revisit an alternative method for eliminating the quantum potential (referred to in this work as the "cancellation approach") in light of the known non-universality of the classical limit. Beyond examining conservation laws via Lagrangian field theory, we identify its deeper connection to a generalized Lagrangian field theory, which offers a more straightforward route to constructing a Lagrangian density in terms of the components of a two-component wave function for rotational inviscid flow. Finally, we discuss the completeness of Clebsch parameterization, concluding our evaluation of the applicability of the proposed SF-variant formulation.

R. J. Donnelly