Doublevaluedness in Cosmology

Abstract

In a Schwarzschild field, the use of an isotropic radial coordinate r produces a doublevalued description of space in that at a given time two values of r correspond to the same spatial point. We show that a similar doublevaluedness is present in a bound or unbound Friedmann-Robertson-Walker universe when it is described with an isotropic radial coordinate. This has important implications in cosmology when isotropic coordinates are used for describing distant galaxies in bound and unbound universe models.