On the Viability of Bianchi Type VIIh Models with Dark Energy

We generalize the predictions for the CMB anisotropy patterns arising in Bianchi type VIIh universes to include a dark energy component. We consider these models in light of the result of Jaffe et al. (2005a,b) in which a correlation was found on large angular scales between the WMAP data and the anisotropy structure in a low density Bianchi universe. We find that by including a term Omega_L > 0, the same best-fit anisotropy pattern is reproduced by several combinations of cosmological parameters. This sub-set of models can then be further constrained by current observations that limit the values of various cosmological parameters. In particular, we consider the so-called geometric degeneracy in these parameters imposed by the peak structure of the WMAP data itself. Apparently, despite the additional freedom allowed by the dark energy component, the modified Bianchi models are ruled out at high significance.