Refined Madelung Equations

TL;DR

This paper refines the Madelung equations by interpreting functions based on the real part of the wavefunction, leading to new insights into quantum fluid dynamics and angular momentum in hydrogen atom states.

Contribution

It introduces a refined Madelung equation with real-part based interpretations, revealing complex velocity components and angular momentum in quantum fluids.

Findings

Fluid velocity in hydrogen states includes radial and vortex components.

Two related velocities are identified: real and imaginary parts of a complex velocity.

Derived an Euler equation for quantum systems from the refined Madelung equation.

Abstract

The Madelung equations are two equations that are equivalent to the one-body time-dependent Schroedinger equation. In this paper, the Madelung equation, whose gradient is an Euler equation, is refined by introducing interpretations of functions that are shown to depend only on the real-part of the complex-valued wavefunction. These interpretations are extensions of functions from the recently derived generalized Bernoulli equation, applicable to real-valued quantum-mechanical stationary states. In particular, the velocity and pressure definitions are extended so that they depend on the real-part of a time-dependent complex-valued wavefunction. The Bohn quantum potential is then interpreted as the sum of two terms, one involving the kinetic energy and the other involving the pressure. Substituting the interpreted quantum-potential into the Madelung equation gives a refined equation containing two kinetic energy terms, a pressure term, and the external potential. It is easily demonstrated that the refined Madelung equation, applied to the hydrogen atom states with a nonzero magnetic quantum number, gives a fluid velocity that contains both a radial component and a free vortex. Hence, the fluid particles have angular momentum and move on streamlines that terminate at infinity. It is also demonstrated that the two velocities from the refined Madelung equation are related: One is the real component and the other is the imaginary component of a complex velocity. Furthermore, an Euler equation for quantum mechanical systems is derived by taking the gradient of the refined Madelung equation.