Abstract
We study primordial anisotropies generated in the model of gauged hybrid inflation in which the complex waterfall field is charged under a U(1)gauge field.Primordial anisotropies are generated either actively during inflation or from inhomogeneities modulating the surface of end of inflation during waterfall transition.We present a consistent δN mechanism to calculate the anisotropic power spectrum and bispectrum.We show that the primordial anisotropies generated at the surface of end of inflation do not depend on the number of e-folds and therefore do not produce dangerously large anisotropies associated with the IR modes. Furthermore, one can find the parameter space that the anisotropies generated from the surface of end of inflation cancel the anisotropies generated during inflation, therefore relaxing the constrains on model parameters imposed fromIR anisotropies. We also show that the gauge field fluctuations induce a red-tilted power spectrum so the averaged power spectrum from the gauge field can change the total power spectrum from blue to red. Therefore, hybrid inflation, once gauged under a U(1) field, can be consistent with the cosmological observations.
Highlights
Precision observations from WMAP [1, 2] and PLANCK [3, 4] have provided strong supports for inflation as the leading theory for early universe and as a mechanism to generate the primordial seeds for the cosmological structures
The basics predictions of inflation are near scale-invariant, near Gaussian and near adiabatic perturbations on Cosmic Microwave Background (CMB) which are well consistent with the recent cosmological observations
We study the model of gauged hybrid inflation in which the waterfall is a complex scalar field coupled to the U (1) gauge field
Summary
Precision observations from WMAP [1, 2] and PLANCK [3, 4] have provided strong supports for inflation as the leading theory for early universe and as a mechanism to generate the primordial seeds for the cosmological structures. An interesting mechanism in generating quadrupolar asymmetry in primordial power spectrum is to consider anisotropic inflation in the presence of a U (1) gauge field. The idea of generating primordial anisotropy at the surface of end of inflation was pioneered by Yokoyama and Soda in [30] In this scenario, the surface of end of inflation is controlled by the waterfall field which is coupled to a U (1) gauge field. It is argued in [30] that the inhomogeneities sourced by the gauge field fluctuations δAμ at the surface of end of inflation can lead to statistical anisotropies In the spirit this is similar to idea used in [55] to generate curvature perturbations at the end of inflation for models containing interacting scalar fields. We relegates some technicalities of the δN analysis into Appendices
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