which quantities become equal to Hx ... Ex in the case of the special relativity theory, and besides
J1 = ix ... J4 = ρ
we get instead of (63)
{ rot H′ - ∂E′/∂t = i
(63a) {
{ div E′ = ρ
The equations (60), (62) and (63) give thus a generalisation of Maxwell’s field-equations in vacuum, which remains true in our chosen system of co-ordinates.
The energy-components of the electro-magnetic field.
Let us form the inner-product
(65) Kσ = Fσμ Jμ.