Sachs-Wolfe at second order: the CMB bispectrum on large angular scales

By Lotfi Boubekeur, P. Creminelli, Guido D’Amico, J. Noreña, F. Vernizzi. 2009

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We calculate the Cosmic Microwave Background anisotropy bispectrum on large angular scales in the absence of primordial non-Gaussianities, assuming exact matter dominance and extending at second order the classic Sachs-Wolfe result δT/T = Φ/3. The calculation is done in Poisson gauge. Besides intrinsic contributions calculated at last scattering, one must consider integrated effects. These are associated to lensing, and to the time dependence of the potentials (Rees-Sciama) and of the vector and tensor components of the metric generated at second order. The bispectrum is explicitly computed in the flat-sky approximation. It scales as l−4 in the scale invariant limit and the shape dependence of its various contributions is represented in 3d plots. Although all the contributions to the bispectrum are parametrically of the same order, the full bispectrum is dominated by lensing. In the squeezed limit it corresponds to fNLlocal = −1/6−cos(2θ), where θ is the angle between the short and the long modes; the angle dependent contribution comes from lensing. In the equilateral limit it corresponds to fNLequil ≃ 3.13.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a6a1ac7edae2e9e48b60a6520e054316f9510e64

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Citations in the corpus

Tachyon effective actins in open string theory (2003, background): “It was then argued in [33] that the effective action (1.”
SEVEN-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP) OBSERVATIONS: COSMOLOGICAL INTERPRETATION (2010, background): “…Carroll 1996; Mollerach & Matarrese 1997; Bartolo et al. 2006, 2007; Pitrou 2009a,b) are expected to give f localNL ∼ 1 (Nitta et al. 2009; Senatore et al. 2009a,b; Khatri & Wandelt 2009a,b; Boubekeur et al. 2009; Pitrou et al. 2008) and are negligible given the noise level of the WMAP 7-year data.”
Planck 2018 results. IX. Constraints on primordial non-Gaussianity (2019, background): “…the Planck data set its expected impact is very small both in temperature (Bartolo et al. 2004b; Creminelli & Zaldarriaga 2004; Bartolo et al. 2005; Boubekeur et al. 2009; Nitta et al. 2009; Senatore et al. 2009; Khatri & Wandelt 2009; Bartolo & Riotto 2009; Khatri & Wandelt 2010; Bartolo et al.…”