Page:Grundgleichungen (Minkowski).djvu/45



Now if we make use of (59), and denote the space-vector which has $$\Omega_{1},\ \Omega_{2},\ \Omega_{3}$$ as the x-, y-, z-components by the symbol $$\mathfrak{W}$$, then the third component of 92) can be expressed in the form

The round bracket denoting the scalar product of the vectors within it.

§ 14. The Ponderomotive Force.
Let us now write out the relation $$K = lor\ S = -sF + N$$ in a more practical form; we have the four equations

It is my opinion that when we calculate the ponderomotive force which acts upon a unit volume at the space-time point x,y,z,t, it has got x-, y-, z-