Nonpropagating string excitations

It is shown that certain force distributions applied to a finite portion of an infinitely long string do not produce any excitation outside the region of the applied force. The existence of such nonpropagating excitations is demonstrated by a simple example, and two general theorems concerning their nature are proven. Some analogies between nonpropagating string excitations and fields produced by nonradiating sources are noted. (C) 1998 American Association of Physics Teachers.