four-vector potential, the harmonic gauge replaces the electromagnetic Lorenz gauge, the field equations are , and the retarded-wave solution is Using SI units, the expression must be divided by , as can be confirmed by dimensional analysis. Occurrence and application A many-body theory which includes an average of retarded and advanced Liénard–Wiechert potentials is the Wheeler–Feynman absorber theory also known as the Wheeler–Feynman time-symmetric theory. Example The potential of charge with uniform speed on a straight line has inversion in a point that is in the recent position. The potential is not changed in the direction of movement. See also Maxwell's equations Liénard–Wiechert potential Lenz's law References Potentials