Revisiting constraints on (pseudo)conformal Universe with Planck data

TL;DR

This paper uses Planck data to set new constraints on the (pseudo)conformal Universe model, especially regarding statistical anisotropy, with the strongest limits found in scenarios with a long intermediate evolution after symmetry breaking.

Contribution

It provides updated observational constraints on the (pseudo)conformal Universe model using Planck temperature maps and quadratic maximal likelihood estimators.

Findings

Strongest constraint on coupling constant in models with intermediate evolution

Weaker limits in models without intermediate stage, allowing larger coupling constants

Non-Gaussianity in the 4-point function may serve as a better signature in some scenarios

Abstract

We revisit constraints on the (pseudo)conformal Universe from the non-observation of statistical anisotropy in the Planck data. The quadratic maximal likelihood estimator is applied to the Planck temperature maps at frequencies 143 GHz and 217 GHz as well as their cross-correlation. The strongest constraint is obtained in the scenario of the (pseudo)conformal Universe with a long intermediate evolution after conformal symmetry breaking. In terms of the relevant parameter (coupling constant), the limit is h^2 <0.0013 at 95% C.L. (using the cross-estimator). The analogous limit is much weaker in the scenario without the intermediate stage (h^2 \ln \frac{H_0}{\Lambda}<0.52) allowing the coupling constant to be of order one. In the latter case, the non-Gaussianity in the 4-point function appears to be a more promising signature.