Hunting for primordial non-Gaussianity in the cosmic microwave background

By E. Komatsu. 2010

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Since the first limit on the (local) primordial non-Gaussianity parameter, fNL, was obtained from the Cosmic Background Explorer (COBE) data in 2002, observations of the cosmic microwave background (CMB) have been playing a central role in constraining the amplitudes of various forms of non-Gaussianity in primordial fluctuations. The current 68% limit from the 7-year data of the Wilkinson Microwave Anisotropy Probe (WMAP) is fNL = 32 ± 21, and the Planck satellite is expected to reduce the uncertainty by a factor of 4 in a few years from now. If fNL ≫ 1 is found by Planck with high statistical significance, all single-field models of inflation would be ruled out. Moreover, if the Planck satellite finds fNL ∼ 30, then it would be able to test a broad class of multi-field models using the 4-point function (trispectrum) test of τNL ⩾ (6fNL/5)2. In this paper, we review the methods (optimal estimator), results (WMAP 7-year) and challenges (secondary anisotropy, second-order effect and foreground) of measuring primordial non-Gaussianity from the CMB data, present a science case for the trispectrum and conclude with future prospects.

Subfields: Astronomy and Astrophysics, Oceanography

View Paper: https://www.semanticscholar.org/paper/09be98f12f37b6e7c284abbc0ef07a0bfaab34d5

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Citations in the corpus

Cosmological Parameters from Observations of Galaxy Clusters (2011, background): “(See Chen 2010 and Komatsu 2010 for recent reviews.)”
The clustering of galaxies in the SDSS-III DR9 Baryon Oscillation Spectroscopic Survey: constraints on primordial non-Gaussianity (2012, background): “Komatsu (2010) and Creminelli et al. (2011) have shown that, for standard, single-field inflation, the amplitude of the bispectrum in the “squeezed” limit becomes vanishingly small, and thus any detected scale-dependent bias at large-scales would disprove all single-field models, subject to the…”
CMB from CFT (2012, background): “We refer the reader to [1, 2] for a review of these developments and to [3] for background material.”
Constraining primordial non-Gaussianity with future galaxy surveys (2011, methodology): “The most well-established method to constrain PNG is to measure the 3-point statistics of the CMB temperature anisotropies (Komatsu 2010).”
ACTPol: a polarization-sensitive receiver for the Atacama Cosmology Telescope (2010, background): “It is widely believed that if the model is incomplete or incorrect the first hints will come through the detection of non-Gaussianity.(22) To date there are only upper limits on non-Gaussianity.”
The clustering of galaxies in the SDSS‐III Baryon Oscillation Spectroscopic Survey: cosmological implications of the large‐scale two‐point correlation function (2012, background): “…of the Universe or details of inflationary physics (Percival et al. 2002; Tegmark et al. 2004; Cole et al. 2005; Sánchez et al. 2006; Spergel et al. 2007; Komatsu et al. 2009; Komatsu 2010; Percival et al. 2010; Reid et al. 2010a; Keisler et al. 2011; Blake et al. 2011; Montesano et al. 2012).”
Formation of Galaxy Clusters (2012, background): “The current CMB constraint on scaleindependent non-Gaussianity isfNL = 30± 20 at the 68% confidence level (e.g., Komatsu 2010) and there is thus still room for existence of sizable deviations from Gaussianity.”
COrE (Cosmic Origins Explorer) A White Paper (2011, background): “Cosmic microwave background non-Gaussianity is emerging as a powerful new probe of the origin of cosmic structures in the very early Universe and their subsequent evolution (see for example the reviews in [75, 76, 77, 78, 79]).”
Planck 2015 results. XVII. Constraints on primordial non-Gaussianity (2015, unknown): “Primordial NG is one of the most powerful tests of inflation, and more generally of high-energy early Universe physics (for some reviews, see Bartolo et al. 2004a; Liguori et al. 2010; Chen 2010b; Komatsu 2010; Yadav & Wandelt 2010).”
Review of local non-Gaussianity from multi-field inflation (2010, methodology): “Constraints are expected to improve rapidly and significantly, first with Planck data and later using large scale structure data, see the recent reviews [3–5].”
Planck 2018 results. IX. Constraints on primordial non-Gaussianity (2019, methodology): “For more details about specific realizations of inflationary models within each class, see the previous two Planck papers on primordial NG (PCNG13; PCNG15) and reviews (e.g., Bartolo et al. 2004a; Liguori et al. 2010; Chen 2010b; Komatsu 2010; Yadav & Wandelt 2010).”