Polarized Spots in Anisotropic Open Universes

TL;DR

This paper explores how anisotropic Bianchi universe models can produce localized temperature and polarization features in the CMB, potentially explaining observed anomalies like the WMAP cold spot.

Contribution

It demonstrates that Bianchi V and VII_h models can generate localized temperature features and polarization patterns, with unique polarization rotation effects in Bianchi VII_h.

Findings

Localized temperature features can arise in Bianchi V and VII_h models.

Bianchi VII_h models can rotate polarization angles, converting E modes into B modes.

Models can produce observable temperature and polarization patterns without conflicting with current data.

Abstract

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 VII$_{h}$. Both these models also generate coherent polarization patterns. In Bianchi VII$_h$, however, rotation of the polarization angle as light propagates along geodesics can convert E modes into B modes but in Bianchi V this is not necessarily the case. It is in principle possible, therefore, to generate localized temperature features without violating existing observational constraints on the odd-parity component of the polarization of the cosmic microwave background.