Cosmic microwave background constraints on cosmological models with
  large-scale isotropy breaking
  Several anomalies appear to be present in the large-angle cosmic microwave
background (CMB) anisotropy maps of WMAP, including the alignment of
large-scale multipoles. Models in which isotropy is spontaneously broken (e.g.,
by a scalar field) have been proposed as explanations for these anomalies, as
have models in which a preferred direction is imposed during inflation. We
examine models inspired by these, in which isotropy is broken by a
multiplicative factor with dipole and/or quadrupole terms. We evaluate the
evidence provided by the multipole alignment using a Bayesian framework,
finding that the evidence in favor of the model is generally weak. We also
compute approximate changes in estimated cosmological parameters in the
broken-isotropy models. Only the overall normalization of the power spectrum is
modified significantly.
