Causal bounds on cosmological angular correlation

Kavli Affiliate: Craig Hogan

| First 5 Authors: Craig Hogan, Ohkyung Kwon, Stephan S. Meyer, Nathaniel Selub, Frederick Wehlen

| Summary:

We test the hypothesis that angular correlations of gravitationally-induced
temperature anisotropy in the cosmic microwave background (CMB) vanish over a
range of large angular separations constrained by causality. Standard conformal
geometry is used to show that if primordial quantum fluctuations generate
physical correlations of gravitational potential only within compact causal
diamonds bounded by inflationary horizons, the angular correlation function
$C(Theta)$ of gravitationally-induced CMB anisotropy should exactly vanish
over a significant range of angular separation around $Theta= 90^circ$. This
geometrical causal symmetry is shown to be consistent with CMB correlations in
all-sky maps from the WMAP and Planck satellites, after accounting for the
unmeasured dipole component and systematic measurement errors. Most
significantly, the even-parity component of correlation $C_{even}(Theta)$ is
shown to be much closer to zero than previously documented, and orders of
magnitude less than standard expectations. This occurrence is extremely
unlikely in standard cosmological realizations based on a quantum field model:
within the computed causal shadow, $Theta= pi/2 pm arcsin(1/4)$, or
$75.52^circlesssimThetalesssim 104.48^circ$, standard realizations are
shown to produce residual correlations as small as those in the Planck maps
with probabilities that range from $simeq 10^{-4.3}$ to $simeq 10^{-2.8}$.
These results could signify that primordial quantum geometrical fluctuations
obey a causal symmetry not included in the standard quantum field model.

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