Thus, m > 0, m = 0 and m < 0. (The last case is similar to the first.) In 3 + 1 dimensions, when In m > 0, we can write, w = ms for the third invariant, where s represents the spin, or intrinsic angular momentum. More generally, in n + 1 dimensions, the generators L and C will be related, respectively, to the total angular momentum and center-of-mass moment by