BOUNDS ON FIELDS FROM FAST ROTATING SOURCES, AND OTHERS

General bounds are noted on the retarded wave field psi(r, t) from a s ource distribution s(r, t) which is zero outside some volume. Specific ally if s is bounded in magnitude then psi is bounded in magnitude, an d decays far away as r(-1) (or faster). If the first derivatives of s are also bounded and continuous, the same applies to the gradient of t he field. These are unremarkable properties, but being general, contin ue to apply in circumstances where they are less obvious. In particula r they apply to a source distribution which is 'rotating rigidly' at s uch a high angular velocity that the outer parts are moving faster tha n the wave speed c. The bounds contradict some results derived and ana lysed by Ardavan (1984, 1989, 1991a, b, 1994a, b) in terms, mostly, of an associated cusped caustic surface (bent Mach cane).