  Schr{\"o}dinger noticed in 1952 that a scalar complex wave function can be
made real by a gauge transformation. The author showed recently that one real
function is also enough to describe matter in the Dirac equation in an
arbitrary electromagnetic or Yang--Mills field. This suggests some "symmetry"
between positive and negative frequencies and, therefore, particles and
antiparticles, so the author previously considered a description of
one-particle wave functions as plasma-like collections of a large number of
particles and antiparticles. The description has some similarities with Bohmian
mechanics. This work offers a criterion for approximation of continuous charge
density distributions by discrete ones with quantized charge based on the
equality of partial Fourier sums, and an example of such approximation is
computed using the homotopy continuation method. An example mathematical model
of the description is proposed. The description is also extended to composite
particles, such as nucleons or large molecules, regarded as collections
including a composite particle and a large number of pairs of elementary
particles and antiparticles. While it is not clear if this is a correct
description of the reality, it can become a basis of an interesting model or
useful picture of quantum mechanics.
