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Planck 2013 results. XXIV. Constraints on primordial non-gaussianity

  • Author(s): Ade, PAR
  • Aghanim, N
  • Armitage-Caplan, C
  • Arnaud, M
  • Ashdown, M
  • Atrio-Barandela, F
  • Aumont, J
  • Baccigalupi, C
  • Banday, AJ
  • Barreiro, RB
  • Bartlett, JG
  • Bartolo, N
  • Battaner, E
  • Benabed, K
  • Benoît, A
  • Benoit-Lévy, A
  • Bernard, JP
  • Bersanelli, M
  • Bielewicz, P
  • Bobin, J
  • Bock, JJ
  • Bonaldi, A
  • Bonavera, L
  • Bond, JR
  • Borrill, J
  • Bouchet, FR
  • Bridges, M
  • Bucher, M
  • Burigana, C
  • Butler, RC
  • Cardoso, JF
  • Catalano, A
  • Challinor, A
  • Chamballu, A
  • Chiang, HC
  • Chiang, LY
  • Christensen, PR
  • Church, S
  • Clements, DL
  • Colombi, S
  • Colombo, LPL
  • Couchot, F
  • Coulais, A
  • Crill, BP
  • Curto, A
  • Cuttaia, F
  • Danese, L
  • Davies, RD
  • Davis, RJ
  • De Bernardis, P
  • De Rosa, A
  • De Zotti, G
  • Delabrouille, J
  • Delouis, JM
  • Désert, FX
  • Diego, JM
  • Dole, H
  • Donzelli, S
  • Doré, O
  • Douspis, M
  • Ducout, A
  • Dunkley, J
  • Dupac, X
  • Efstathiou, G
  • Elsner, F
  • Enßlin, TA
  • et al.
Abstract

© ESO, 2014. 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-Cl 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 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 τNL< 2800 (95% CL). Taken together, these constraints represent the highest precision tests to date of physical mechanisms for the origin of cosmic structure.

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