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 formulate a new hypothesis for causal coherence of gravitational quantum
fluctuations, and test its predicted constraints on large-scale angular
correlations in the cosmic microwave background (CMB). We posit that {it
quantum fluctuations generate physical correlations of gravitational potential
only within compact causal diamonds bounded by inflationary horizons}. It is
shown that the angular correlation function $C(Theta)$ of
gravitationally-induced CMB anisotropy is thereby constrained by conformally
invariant geometry to exactly vanish at large angular separations: even-parity
correlation vanishes in a range $Theta= pi/2 pm arcsin(1/4)$, and total
correlation vanishes over a larger range that could extend as far as
$Theta=3pi/4$. This geometrical causal symmetry is tested with CMB
correlations in all-sky maps from the {sl WMAP} and {sl Planck} satellites,
allowing for unmeasured dipole anisotropy. Correlations in this range of
angular separation are indeed found to be much smaller than expected in
standard realizations based on local effective quantum field theory, which
produce correlations three to four orders of magnitude larger than those in the
{sl Planck} maps, and deviate as little from zero as the maps do with
probabilities that range from $simeq 10^{-4.3}$ to $simeq 10^{-2.8}$. These
results could indicate that large-angle CMB anisotropy preserves a primordial
causal symmetry of quantum gravity that is not included in the standard quantum
model of inflation.

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