Year: 2016
Type: article
Abstract: If the primordial bispectrum is sufficiently large then the CMB hemispherical power asymmetry may be explained by a large-scale mode of exceptional amplitude which perturbs the ζ two-point function. We extend previous calculations, which were restricted to one- or two-source scenarios, by providing a method to compute the response of the two-point function in any model yielding a `local-like' bispectrum. In general, this shows that it is not the reduced bispectrum f NL ( k 1 , k 2 , k 3 ) which sources the amplitude and scale-dependence of the mode coupling but rather a combination of `response functions'. We discuss why it is difficult to construct successful scenarios and enumerate the fine-tunings which seem to be required. Finally, we exhibit a concrete model which can be contrived to match the observational constraints and show that to a Planck-like experiment it would appear to have | NL local | ∼ | NL equi | ∼ | NL ortho | ≲ 1. Therefore, contrary to previous analyses, we conclude that it is possible to generate the asymmetry while respecting observational constraints on the bispectrum and low-ℓ multipoles even without tuning our location on the long-wavelength mode.
Institution: University of Sussex
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G186000453, G2639239629, G3083174983, G4357913612, DiRAC SMP Facility: The Structure of the Universe, Programs on Critical Problems in Physics, Astrophysics and Biophysics at the Aspen Center for Physics, The COSMOS Consortium: Fundamental Cosmology, Dark Energy and the Cosmic Microwave Sky, The Structure of the Universe: Cosmology, Exoplanets and Lattice QCD - supplementary grant, The Structure of the Universe: Cosmology, Exoplanets and Lattice QCD, DiRAC SMP Facility: Revealing the Structure of the Universe, Astrophysics and Cosmology - Sussex Consolidated Grant, G8896167186
OpenAlex ID: W2138053237