Kavli Affiliate: Craig Hogan
| First 5 Authors: Craig Hogan, Ohkyung Kwon, Stephan S. Meyer, Nathaniel Selub, Frederick Wehlen
| Summary:
The global isotropy of the universe is analyzed on the scale of the cosmic
horizon, using the angular correlation function $C(Theta)$ of cosmic microwave
background (CMB) temperature at large angular separation $Theta$. Even-parity
correlation $C_{even}(Theta)$ is introduced as a direct, precise measure of
horizon-scale cosmic anisotropy, independent of the unknown dipole. Correlation
in maps from {sl Planck} at $Thetasimeq 90^circpm 15^circ$ is found to be
much smaller than in any previous studies. Allowing for measurement errors
introduced by Galaxy subtraction, it is shown to be consistent with zero, with
an absolute value three to four orders of magnitude smaller than expected in
standard theory. Such a small variation from zero is estimated to occur by
chance in a fraction $simeq 10^{-4.3}$ to $simeq 10^{-2.8}$ of standard
realizations. We also consider an alternative interpretation of this result, as
a signature of a new causal symmetry of cosmological initial conditions. The
measured zero-correlation angular interval is derived geometrically by assuming
that quantum fluctuation states have spacelike coherence bounded by compact
causal diamonds, and that they convert into classical perturbations when world
lines cross horizons. This process differs from the unbounded spacelike
coherent evolution and freezing assumed in standard theory. It is argued that
such a scale-invariant causal angular symmetry of initial conditions is broadly
consistent with cosmological measurements on smaller scales.
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