Polarized Spots in Anisotropic Open Universes

We calculate the temperature and polarization patterns generated in anisotropic cosmological models drawn from the Bianchi classification. We show that localized features in the temperature pattern, perhaps similar to the cold spot observed in the Wilkinson Microwave Anisotropy Probe (WMAP) data, can be generated in models with negative spatial curvature, i.e. Bianchi types V and VIIh. Both these models also generate coherent polarization patterns. In Bianchi VIIh, however, rotation of the polarization angle as light propagates along geodesics can convert E modes into B modes but in Bianchi V this does not happen. It is in principle possible, therefore, to generate localized temperature features without violating existing observational constraints on the polarization of the cosmic microwave background. PACS numbers: 98.80.Es, 98.80.Jk Submitted to: Class. Quantum Grav.