Constraining anisotropic models of the early Universe with WMAP9 data

Abstract

We constrain several models of the early Universe that predict a statistical anisotropy of the cosmic microwave background (CMB) sky. We make use of WMAP9 maps deconvolved with beam asymmetries. As compared to previous releases of WMAP data, they do not exhibit the anomalously large quadrupole of statistical anisotropy. This allows to strengthen the limits on the parameters of models established earlier in the literature. In particular, the amplitude of the special quadrupole is constrained as |g_*|<0.072 at 95% C.L. (-0.046<g_*<0.048 at 68% C.L.) independently of the preferred direction in the sky. The upper limit is obtained on the total number of e-folds in anisotropic inflation with the Maxwellian term nonminimally coupled to the inflaton, namely N_{tot} <N_{CMB} +82 at 95% C.L. (+14 at 68% C.L.) for N_{CMB}=60. We also constrain models of the (pseudo)conformal universe. The strongest constraint is obtained for spectator scenarios involving a long stage of subhorizon evolution after conformal rolling, which reads h^2 < 0.006 at 95% C.L., in terms of the relevant parameter. The analogous constraint is much weaker in dynamical models, e.g., Galilean genesis.