Byrnes, Christian T, Regan, Donough, Seery, David and Tarrant, Ewan R M (2016) The hemispherical asymmetry from a scale-dependent inflationary bispectrum. Journal of Cosmology and Astroparticle Physics, 2016 (06). 025. ISSN 1475-7516
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Abstract
If the primordial bispectrum is sufficiently large then the CMB hemispherical asymmetry may be explained by a large-scale mode of exceptional amplitude which perturbs the zeta 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 fNL 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 |fNL-local| ~ |fNL-equi| ~ |fNL-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-ell multipoles even without tuning our location on the long-wavelength mode.
Item Type: | Article |
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Schools and Departments: | School of Mathematical and Physical Sciences > Physics and Astronomy |
Subjects: | Q Science > QB Astronomy > QB0980 Cosmogony. Cosmology |
Depositing User: | David Seery |
Date Deposited: | 13 Jun 2016 06:01 |
Last Modified: | 02 Jul 2019 19:21 |
URI: | http://sro.sussex.ac.uk/id/eprint/61311 |
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📧 Request an updateProject Name | Sussex Project Number | Funder | Funder Ref |
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Precisions tests of the inflationary scenario | G0918 | EUROPEAN UNION | 308082 |
Astrophysics and Cosmology - Sussex Consolidated Grant | G1291 | STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCIL | ST/L000652/1 |