A PROBE OF PRIMORDIAL GRAVITY-WAVES AND VORTICITY

A formalism for describing an all-sky map of the polarization of the c osmic microwave background is presented. The polarization pattern on t he sky can be decomposed into two geometrically distinct components. O ne of these components is not coupled to density inhomogeneities. A no nzero amplitude for this component of polarization can only be caused by tensor or vector metric perturbations. This allows unambiguous iden tification of long-wavelength gravity waves or large-scale vortical fl ows at the time of last scattering.