Revisiting a pre-inflationary radiation era and its effect on the CMB power spectrum (original) (raw)

2015, Journal of Cosmology and Astroparticle Physics

We revisit the scenario where inflation is preceded by a radiation era by considering that the inflaton too could have been in thermal equilibrium early in the radiation era. Hence we take into account not only the effect of a pre-inflationary era on the inflaton mode functions but also that of a frozen thermal distribution of inflaton quanta. We initially discuss in detail the issues relevant to our scenario of a pre-inflationary radiation dominated era and then obtain the scalar power spectrum for this scenario. We find that the power spectrum is free from infrared divergences. We then use the WMAP and Planck data to determine the constraints on the inflaton comoving 'temperature' and on the duration of inflation. We find that the best fit value of the duration of inflation is less than 1 e-folding more than what is required to solve cosmological problems, while only an upper bound on the inflaton temperature can be obtained. Contents 1 Introduction 1 2 Pre-inflationary radiation era 3 2.1 The little horizon problem 3 2.2 The little flatness problem 3 2.3 Local thermodynamic equilibrium 4 2.4 Small Φ 5 2.5 Initial conditions for the mode functions 6 2.6 Thermal initial state 6 3 Evolution of perturbations 8 3.1 Subhorizon primordial perturbations in the pre-inflationary radiation era 9 3.1.1 Justification for largeã 10 3.2 Evolution of primordial perturbations during inflation 11 3.3 Mode function matching and the power spectrum 12 3.4 Infrared divergences 16 4 Parameter estimation 17 5 Discussion and Conclusions 21

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