Effects of a pre-inflation radiation-dominated epoch to CMB anisotropy

Abstract

We consider that the pre-inflation era is radiation-dominated, transiting smoothly to the inflationary era. We work out in detail the dynamics of inflaton fluctuations across the phase transition and the proper choices of initial vacuum states. It is found that this phase transition can suppress long-wavelength quantum fluctuations of inflaton. This may attribute to the large-scale CMB anisotropy a lower power than predicted in the standard $\Lambda$CDM model. In constraining this transitional effect by WMAP anisotropy data, we use the WMAP best-fit scale-invariant $\Lambda$CDM model with the density power spectrum replaced by the one found in this work. We find that the transition occurs at least about 10 e-folds before the comoving scales comparable to our present horizon size cross the Hubble radius during inflation.

paper revised,a new figure is added and new references added

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• Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Temperature Analysis
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• Joint Planck and WMAP Assessment of Low CMB Multipoles
• Revisiting a pre-inflationary radiation era and its effect on the CMB power spectrum
• Hint of a truncated primordial spectrum from the CMB large-scale anomalies
• Analytical investigation of pre-inflationary effects in the primordial power spectrum: From General Relativity to hybrid Loop Quantum Cosmology
• Warm bounce in loop quantum cosmology and the prediction for the duration of inflation
• Choice of vacuum state and the relation between inflationary and Planck scales
• Thermal gravitational-wave background in the general pre-inflationary scenario
• Lowering tensor-to-scalar ratio by pre-inflationary dynamics
• Analytic Approximations for the Primordial Power Spectrum with Israel Junction Conditions
• Primordial perturbations in kinetically dominated regimes of general relativity and hybrid quantum cosmology