6533b82cfe1ef96bd128ed36
RESEARCH PRODUCT
Sachs-Wolfe at second order: the CMB bispectrum on large angular scales
Jorge NoreñaLotfi BoubekeurLotfi BoubekeurLotfi BoubekeurGuido D'amicoFilippo VernizziPaolo Creminellisubject
PhysicsNew horizonsCosmology and Nongalactic Astrophysics (astro-ph.CO)Cosmic microwave backgroundFOS: Physical sciencesAstronomy and AstrophysicsAstrophysics::Cosmology and Extragalactic AstrophysicsCMBR theoryCosmologyMarie curiesymbols.namesakecosmological perturbation theoryGalileo (satellite navigation)symbolsnon-gaussianityBispectrumHumanitiesOrder (virtue)Astrophysics - Cosmology and Nongalactic Astrophysicsdescription
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 delta T/T = Phi/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 f(NL)(local) = -1/6 - cos(2 theta), where theta is the angle between the short and the long modes; the angle dependent contribution comes from lensing. In the equilateral limit it corresponds to f(NL)(equil) similar or equal to 3.13.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2009-08-25 |