Oct 15, 1993 - 7700, Cape Town, South Africa. (Received 17 ... This states that for a quantity to be gauge invariant it must either be ... formation in a richer class of models. This paper is ... 20), and the speed of light is taken to be unity (c = 1). I assume that ... TD and 2, follow by taking the spatial gradients of (6) and (8) (see ...
