Pseudoscalar N-flation and axial coupling revisited

Abstract

We revisit the dynamics of the axial coupling between many N-flatons and an Abelian gauge field, with special attention to its statistically anisotropic signal. The anisotropic power spectrum of curvature perturbations associated to the large wavelength modes of the gauge vector field is generally undetectable, since the anisotropy is confined to small scales. If the gauge field is the electromagnetic field, provided that the number of fields participating in the exponential expansion is large, it could be possible to generate sizable large scale magnetic fields. However, its spectrum is blue, and appreciable power on large scales implies an overly strong field on smaller scales, incompatibly with observations. Furthermore, the anisotropy is also markedly enhanced, and might be at odds with the isotropic observed sky. These aspects further demand that the scale of inflation is kept to a minimum.

14 pages - v2 with minor changes in the conclusions, v3 to match published version

References in corpus (7)

• Planck 2018 results. VII. Isotropy and Statistics of the CMB
• Large Nongaussianity in Axion Inflation
• Magnetic fields from inflation?
• N-flationary magnetic fields
• The Nature of Primordial Fluctuations from Anisotropic Inflation
• Pseudoscalar perturbations and polarization of the cosmic microwave background
• The anisotropy of a three- and a one-form

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• Primordial Statistical Anisotropies: The Effective Field Theory Approach
• The TT, TB, EB and BB correlations in anisotropic inflation
• Light propagation in inhomogeneous and anisotropic cosmologies
• Clustering Fossil from Primordial Gravitational Waves in Anisotropic Inflation
• Stochastic Effects in Anisotropic Inflation
• Vector disformal transformation of cosmological perturbations
• Charged Vector Inflation
• Effective field theory of statistical anisotropies for primordial bispectrum and gravitational waves
• Gravitational Waves from Gauge Quanta Produced during Inflation