Abstract
The Planck nominal mission cosmic microwave background
(CMB) maps yield unprecedented constraints on primordial
non-Gaussianity (NG). Using three optimal bispectrum
estimators, separable template-fitting (KSW), binned, and
modal, we obtain consistent values for the primordial
local, equilateral, and orthogonal bispectrum amplitudes,
quoting as our final result fNLlocal = 2.7 ± 5.8,
fNLequil = -42 ± 75, and fNLorth = -25 ± 39 (68% CL
statistical). Non-Gaussianity is detected in the data;
using skew-C\sub{\ell} statistics we find a nonzero
bispectrum from residual point sources, and the
integrated-Sachs-Wolfe-lensing bispectrum at a level
expected in the {\wedge}CDM scenario. The results are
based on comprehensive cross-validation of these
estimators on Gaussian and non-Gaussian simulations, are
stable across component separation techniques, pass an
extensive suite of tests, and are confirmed by skew-Cl,
wavelet bispectrum and Minkowski functional estimators.
Beyond estimates of individual shape amplitudes, we
present model-independent, three-dimensional
reconstructions of the Planck CMB bispectrum and thus
derive constraints on early-Universe scenarios that
generate primordial NG, including general single-field
models of inflation, excited initial states
(non-Bunch-Davies vacua), and directionally-dependent
vector models. We provide an initial survey of
scale-dependent feature and resonance models. These
results bound both general single-field and multi-field
model parameter ranges, such as the speed of sound, cs =
0.02 (95% CL), in an effective field theory
parametrization, and the curvaton decay fraction rD =
0.15 (95% CL). The Planck data significantly limit the
viable parameter space of the ekpyrotic/cyclic scenarios.
The amplitude of the four-point function in the local
model tNL<2800 (95% CL). Taken together, these
constraints represent the highest precision tests to date
of physical mechanisms for the origin of cosmic
structure.
Original language | English |
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Article number | A24 |
Number of pages | 58 |
Journal | Astronomy and Astrophysics |
Volume | 571 |
DOIs | |
Publication status | Published - 2014 |
MoE publication type | A1 Journal article-refereed |
Keywords
- cosmic background radiation
- cosmology
- early Universe
- inflation
- data analysis