where denotes the number of electrons and the are the wave vectors from within the (discretized) Fermi surface/sphere. Many‐particle effects (due to the electron–electron Coulomb interaction) can be taken into account semi‐phenomenologically through backflow effects, realized through a change to collective variables , where

.

Here, the simple parametrization has desirable asymptotic properties.

If in the resulting function the positions of the first particles are fixed, a real‐valued reduced wave function of results that can be visualized in the 2D case as a contour plot.

The wave vectors within the Fermi sphere are discretized through Born–von Karman boundary conditions applied to the wave function. As a result, there is a one‐to‐one correspondence between the number of electrons and the Fermi wave vector and at certain the wave functions will change their appearance due to the addition of new electrons.

This Demonstration visualizes the square of the absolute value of the reduced wave function as a contour plot on the regions where the reduced wave function is positive or negative. The nodal lines of the resulting one‐particle function are shown as blue curves and the movable white points indicate the fixed electrons at position . Depending on the backflow parameters, the resulting wave function can develop regions with intricate fractal structure.