Constraints on primordial non-Gaussianity

By P. Ade, N. Aghanim, M. Arnaud, F. Arroja, M. Ashdown, J. Aumont, C. Baccigalupi, M. Ballardini, A. Banday, Rita Belén Barreiro and 231 more. 2013

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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 f(NL)(local) = 2.7 +/- 5.8, f(NL)(equil) = -42 +/- 75, and f(NL)(ortho) = 25 +/- 39 (68% CL statistical). Non-Gaussianity is detected in the data; using skew-C 'statistics we find a nonzero bispectrum from residual point sources, and the integrated-Sachs-Wolfe-lensing bispectrum at a level expected in the CDM scenario. The results are based on comprehensive crossvalidation 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-C `, 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 e ff ective 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 NL < 2800 (95% CL). Taken together, these constraints represent the highest precision tests to date of physical mechanisms for the origin of cosmic structure.

Subfields: Astronomy and Astrophysics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/81933d4051e8c03e166f321708e5ba9ad796cfcd

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In Astronomy and Astrophysics

  1. L. Senatore
  2. M. Zaldarriaga
  3. F. Vernizzi
  4. D. Baumann
  5. Xingang Chen
  6. D. Langlois
  7. D. Green
  8. F. Piazza

In Statistical and Nonlinear Physics

  1. L. Senatore
  2. M. Zaldarriaga
  3. D. Green
  4. Andrei Linde
  5. E. Silverstein
  6. F. Vernizzi
  7. D. Langlois
  8. Kendrick M. Smith

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