NORMALIZATION OF MODES IN AN OPEN UNIVERSE

We discuss the appropriate normalization of modes required to generate a homogeneous random held in an open Friedmann-Robertson-Walker unive rse. We consider scalar random fields and certain tensor random fields that can be obtained by covariantly differentiating a scalar. Modes o f interest fall into three categories: the familiar subcurvature modes , the more recently discussed supercurvature modes, and a set of discr ete modes with positive eigenvalues which can be used to generate homo geneous tensor random fields even though the underlying scalar field i s not homogeneous. A particular example of the last case which has bee n discussed in the literature is the bubble wall fluctuation in open i nflationary universes.