Hemispherical Anomaly from Asymmetric Initial States

Abstract

We investigate if the hemispherical asymmetry in the CMB is produced from "asymmetric" 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, $A=0.07\pm 0.022$, we show that the amount of quadrupole terms is roughly equal to $A^2$. The {\it mean} local bispectrum, which gets enhanced for the excited initial state, is within the $1\sigma$ bound of Planck 2015 results for a large field model, $f_{\mathrm{NL}}\simeq 4.17$, 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 $|{\vec{k}}_3|\approx |{\vec{k}}_{l\approx 10}|\ll |{\vec{k}}_1|\approx |{\vec{k}}_2|\approx |{\vec{k}}_{l\approx 2500}|$ with $f_{\mathrm{NL}}^{\min }\approx 3.64$. The maximum occurs when these modes are at the antipode of the preferred pole, $f_{\mathrm{NL}}^{\max }\approx 4.81$ . The difference of non-gaussianity between these two configurations is as large as $\simeq 1.17$ which can be used to distinguish this scenario from other scenarios that try to explain the observed hemispherical asymmetry.

7 pages, double column, 3 figures, v2: references added; v3: Final version to appear in PRD

References in corpus (23)

• Observational Signatures and Non-Gaussianities of General Single Field Inflation
• Enhanced Non-Gaussianity from Excited Initial States
• A Hemispherical Power Asymmetry from Inflation
• Power asymmetry in WMAP and Planck temperature sky maps as measured by a local variance estimator
• Superhorizon Perturbations and the Cosmic Microwave Background
• A Scale-Dependent Power Asymmetry from Isocurvature Perturbations
• Minimum Length Cutoff in Inflation and Uniqueness of the Action
• Energy Transfer in Multi Field Inflation and Cosmological Perturbations
• A Note on Calm Excited States of Inflation
• Non-isotropy in the CMB power spectrum in single field inflation
• On the significance of power asymmetries in Planck CMB data at all scales
• Microwave Background Correlations from Dipole Anisotropy Modulation
• On the Tensor/Scalar Ratio in Inflation with UV Cutoff
• Large-scale anomalies in the cosmic microwave background as signatures of non-Gaussianity
• Inflationary power asymmetry from primordial domain walls
• CMB Hemispherical Asymmetry: Long Mode Modulation and non-Gaussianity
• CMB statistics in noncommutative inflation
• Disformal vectors and anisotropies on a warped brane
• Generating the cosmic microwave background power asymmetry with $g_{NL}$
• CMB hemispherical asymmetry from non-linear isocurvature perturbations
• Negative Running of the Spectral Index, Hemispherical Asymmetry and the Consistency of Planck with Large $r$
• Sensitivity of inflationary predictions to pre-inflationary phases
• Looking for non-Gaussianity in all the right places: A new basis for non-separable bispectra

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• Getting Super-Excited with Modified Dispersion Relations
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• Strongly scale-dependent CMB dipolar asymmetry from super-curvature fluctuations
• Primordial inhomogeneities from massive defects during inflation
• Primordial anisotropies from cosmic strings during inflation
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