Primordial bispectrum information from CMB polarization

By D. Babich, M. Zaldarriaga. 2004

134 citations recorded by the source corpus.

After the precise observations of the cosmic microwave background (CMB) anisotropy power spectrum, attention is now being focused on higher order statistics of the CMB anisotropies. Since linear evolution preserves the statistical properties of the initial conditions, observed non-Gaussianity of the CMB will mirror primordial non-Gaussianity. Single-field slow-roll inflation robustly predicts negligible non-Gaussianity so an indication of primordial non-Gaussianity will suggest alternative scenarios need to be considered. In this paper we calculate the information on primordial non-Gaussianity encoded in the polarization of the CMB. After deriving the optimal weights for a cubic estimator we evaluate the signal-to-noise ratio (S/N) of the estimator for Wilkinson Microwave Anisotropy Probe, Planck, and an ideal cosmic variance limited experiment. We find that when the experiment can observe CMB polarization with good sensitivity, the sensitivity to primordial non-Gaussianity increases by roughly a factor of 2. We also test the weakly non-Gaussian assumption used to derive the optimal weight factor by calculating the degradation factor produced by the gravitational lensing induced connected four-point function. The physical scales in the radiative transfer functions are largely irrelevant for the constraints on the primordial non-Gaussianity. We show that the total (S/N){sup 2} is simply proportional to the number ofmore » observed pixels on the sky.« less

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/37af6de056386f0c2237207c7103e43f8e1b8376

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Citations in the corpus

Primordial Non-Gaussianity and Bispectrum Measurements in the Cosmic Microwave Background and Large-Scale Structure (2010, methodology): “Like single field slow-roll inflation, the predicted ‘non-local’ shape function is a combination of a dominant local shape (II.13) and an equilateral shape (III.53) (see, for example, Barnaby & Cline, 2008; Halliwell, 1993; Seery et al., 2008; Zaldarriaga, 2004).”
Signatures of Initial State Modifications on Bispectrum Statistics (2009, unknown): “40 44 v2 [ he p- th ] Contents”
Non-Gaussianity in curvaton models with nearly quadratic potentials (2005, unknown): “∗E-mail: kari.enqvist@helsinki.fi †E-mail: sami.nurmi@helsinki.fi Contents”
Non-Gaussianities in single field inflation and their optimal limits from the WMAP 5-year data (2009, background): “These error bars are expected to decrease by a factor of six in the next few years when the data from the Planck satellite will be available [48].”
Planck 2018 results. IX. Constraints on primordial non-Gaussianity (2019, methodology): “However, it was shown by Babich & Zaldarriaga (2004), and later confirmed by Lewis et al. (2011), that the contribution from the connected four-point function induced by lensing can become an important contribution to the covariance.”
CMB-S4 Science Case, Reference Design, and Project Plan (2019, background): “Note that these forecasts assume that CMB-S4 can be combined with large-scale measurements from Planck, the impact of secondaries [116] can be reduced, and temperature and polarization can be sufficiently delensed to remove large contributions to the variance [117].”
The bispectrum of galaxies from high-redshift galaxy surveys: Primordial non-Gaussianity and non-linear galaxy bias (2007, background): “NL ≃ 3 (Komatsu & Spergel 2001; Babich & Zaldarriaga 2004; Yadav et al. 2007).”
Primordial Non-Gaussianity (2019, unknown): “[145] Daniel Babich and Matias Zaldarriaga.”
On the consistency relation of the three-point function in single-field inflation (2007, background): “This will reduce the current limit from WMAP 3yr data [11] by a factor of around 6 [25].”
Algorithms for bispectra: Forecasting, optimal analysis, and simulation (2006, background): “A second reason that the assumption of weak non-Gaussianity might break down is that the lensed CMB is non-Gaussian; e.g. in Babich & Zaldarriaga (2004), it is argued that this may degrade constraints on f NL by ∼25 per cent at Planck sensitivity.”
Large-scale non-Gaussian mass function and halo bias: tests on N-body simulations (2009, methodology): “This confirms that constraints on fNL for non-Gaussianity of the local type, achievable using the non-Gaussian halo bias, are competitive with CMB constraints (fNL ∼ 5 for Planck and fNL ∼ 3 for a CMB Pol-type mission; Babich & Zaldarriaga 2004; Yadav, Komatsu & Wandelt 2007).”
Limits on non-Gaussianities from WMAP data (2005, background): “In addition polarization measurements by Planck can further reduce the range by an additional factor of 1.6 [ 29 ].”