Isocurvature and Curvaton Perturbations with Red Power Spectrum and Large Hemispherical Asymmetry

Abstract

We calculate the power spectrum and hemispherical asymmetry of isocurvature and curvaton perturbations due to a complex field Φwhich is evolving along the tachyonic part of its potential. Using a semi-classical evolution of initially sub-horizon quantum fluctuations, we compute the power spectrum, mean field and hemispherical asymmetry as a function of the number of e-foldings of tachyonic growth ΔN and the tachyonic mass term cH^2. We find that a large hemispherical asymmetry due to the modulation of |Φ| can easily be generated via the spatial modulation of |Φ| across the horizon, with Delta |Φ|/|Φ| > 0.5 when the observed Universe exits the horizon within 10-40 e-foldings of the beginning of tachyonic evolution and c is in the range 0.1-1. The spectral index of the isocurvature and curvaton perturbations is generally negative, corresponding to a red power spectrum. Dark matter isocurvature perturbations due to an axion-like curvaton with a large hemispherical asymmetry may be able to explain the hemispherical asymmetry observed by WMAP and Planck. In this case, the red spectrum can additionally suppress the hemispherical asymmetry at small scales, which should make it easier to satisfy scale-dependence requirements on the asymmetry from quasar number counts.

12 pages, 2 figures; additional references; typos and error in rms integration pre-factor corrected, conclusions unaltered

References in corpus (5)

• Hemispherical power asymmetry in the three-year Wilkinson Microwave Anisotropy Probe sky maps
• A Hemispherical Power Asymmetry from Inflation
• Superhorizon Perturbations and the Cosmic Microwave Background
• Constraints on cosmic hemispherical power anomalies from quasars
• A Scale-Dependent Power Asymmetry from Isocurvature Perturbations

Cited by in corpus (22)

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• Hemispherical Asymmetry and Local non-Gaussianity: a Consistency Condition
• Microwave Background Correlations from Dipole Anisotropy Modulation
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• CMB dipole asymmetry from a fast roll phase
• 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
• Pre-inflationary primordial perturbations
• Hemispherical Power Asymmetry from a Space-Dependent Component of the Adiabatic Power Spectrum
• Expected dipole asymmetry in CMB polarization
• Hemispherical Power Asymmetry from Scale-Dependent Modulated Reheating
• CMB hemispherical asymmetry from non-linear isocurvature perturbations
• Scale-dependent CMB asymmetry from primordial configuration
• Lensing as a Probe of Early Universe: from CMB to Galaxies
• Scale-dependent hemispherical asymmetry from general initial state during inflation
• Coupling structure of multi-field primordial perturbations
• Testing the scale-dependent hemispherical asymmetry with the 21-cm power spectrum from the epoch of reionization
• Scale-dependent CMB power asymmetry from primordial speed of sound and a generalized $\delta$N formalism
• Primordial inhomogeneities from massive defects during inflation
• Primordial anisotropies from cosmic strings during inflation
• Isotropic non-Gaussian $g_{\mathrm{NL}}$-like toy models that reproduce the cosmic microwave background anomalies