Temperature anisotropy of the cosmic microwave background offers a test of the fundamental symmetry of spacetime during cosmic inflation. Violation of rotational symmetry yields a distinct signature in the power spectrum of primordial fluctuations as P(\mathbf k)=P_0(k)[1+g_* (\hat k \cdot \hat E_cl)^2], where \hat E_cl is a preferred direction in space and g_* is an amplitude. Using the Planck 2013 temperature maps, we find no evidence for violation of rotational symmetry, g_* = 0.002 \pm 0.016 (68% CL), once the known effects of asymmetry of the Planck beams and Galactic foreground emission are removed.
Date added: Tue, 8 Oct 13