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Hemispherical Asymmetry from Parity-Violating Excited Initial States
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
(English)Article in journal (Refereed) Submitted
Abstract [en]

We investigate if the hemispherical asymmetry in the CMB is produced from parity-violating excited initial condition. We show that in the limit where the deviations from the Bunch-Davies vacuum is large and the scale of new physics is maximally separated from the inflationary Hubble parameter, the primordial power spectrum is modulated only by position dependent dipole and quadrupole terms. Requiring the dipole contribution in the power spectrum to account for the observed power asymmetry, A=0.07±0.022" style="position: relative;" tabindex="0" id="MathJax-Element-1-Frame" class="MathJax">A=0.07±0.022, we show that the amount of quadrupole terms is roughly equal to A2" style="position: relative;" tabindex="0" id="MathJax-Element-2-Frame" class="MathJax">A2. The mean local bispectrum, which gets enhanced for the excited initial state, is within the 1σ" style="position: relative;" tabindex="0" id="MathJax-Element-3-Frame" class="MathJax">1σ bound of Planck 2015 results for a large field model, fNL≃4.17" style="position: relative;" tabindex="0" id="MathJax-Element-4-Frame" class="MathJax">fNL≃4.17, but is reachable by future CMB experiments. The amplitude of the local non-gaussianity modulates around this mean value, depending on the angle that the correlated patches on the 2d CMB surface make with the preferred direction. The amount of variation minimizes for the configuration in which the short and long wavelengths modes are around the preferred pole and |k→3|≈|k→l≈10|≪|k→1|≈|k→2|≈|k→l≈2500|" style="position: relative;" tabindex="0" id="MathJax-Element-5-Frame" class="MathJax">|k⃗ 3|≈|k⃗ l≈10|≪|k⃗ 1|≈|k⃗ 2|≈|k⃗ l≈2500| with fNLmin≈3.64" style="position: relative;" tabindex="0" id="MathJax-Element-6-Frame" class="MathJax">fminNL≈3.64. The maximum occurs when these modes are at the antipode of the preferred pole, fNLmax≈4.81" style="position: relative;" tabindex="0" id="MathJax-Element-7-Frame" class="MathJax">fmaxNL≈4.81 . The difference of non-gaussianity between these two configurations is as large as ≃1.17" style="position: relative;" tabindex="0" id="MathJax-Element-8-Frame" class="MathJax">≃1.17 which can be used to distinguish this scenario from other scenarios that try to explain the observed hemispherical asymmetry.

National Category
Subatomic Physics
Research subject
Theoretical Physics
Identifiers
URN: urn:nbn:se:uu:diva-287835OAI: oai:DiVA.org:uu-287835DiVA: diva2:923516
Available from: 2016-04-26 Created: 2016-04-26 Last updated: 2016-04-26

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