期刊
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
卷 -, 期 11, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1475-7516/2011/11/025
关键词
non-gaussianity; CMBR theory
资金
- Science and Technology Facilities Council [ST/H002774/1] Funding Source: researchfish
- STFC [ST/H002774/1] Funding Source: UKRI
The CMB bispectrum generated by second-order effects at recombination can be calculated analytically when one of the three modes has a wavelength much longer than the other two and is outside the horizon at recombination. This was pointed out in [1] and here we correct their results. We derive a simple formula for the bispectrum, f(NL)(loc) = -(1/6 + cos 2 theta) . (1 - 1/2 . d ln(l(S)(2)C(S))/d ln l(S)), where C-S is the short scale spectrum and theta the relative orientation between the long and the short modes. This formula is exact and takes into account all effects at recombination, including recombination-lensing, but neglects all late-time effects such as ISW-lensing. The induced bispectrum in the squeezed limit is small and will negligibly contaminate the Planck search for a local primordial signal: this will be biased only by f(NL)(loc) approximate to -0.4. The above analytic formula includes the primordial non-Gaussianity of any single-field model. It also represents a consistency check for second-order Boltzmann codes: we find substantial agreement with the current version of the CMBquick code.
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