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Initial Conditions and Inflation The one factor affecting the shape of the power spectra that involves exotic physics is the assumed model of structure formation, which determines how variations in the primordial plasma were created in the first place. Rather than detailing the zoo of proposed structure formation models, only the adiabatic inflationary model will be considered here (this choice of model is motivated by the fact that it fits the observed temperature anisotropies better than the others). Inflationary models generate density perturbations through the rapid growth of quantum fluctuations during the inflationary epoch. The perturbations generated in this way have a very simple structure: random gaussian noise with a nearly scale-invariant spectrum. Adiabatic models further stipulate that while the overall density of the universe varied, the fraction of the material in any particular form (neutrinos, photons, baryons, cold dark matter, etc.) was initially a constant throughout space. Since the variations in the densities of different components did not cancel each other out, this model also yields fluctuations in the curvature of space-time (i.e. the gravitational potential). Therefore, in the adiabatic inflationary scenario, a well defined pattern of initial perturbations was created in the first fraction of a second after the big bang. The Origin of Cosmological Polarization The Structure of Cosmological Polarization Power Spectra and the Structure of CMB Anisotropies Initial Conditions and Inflation The Evolution of Perturbations and Acoustic Oscillations Acoustic Oscillations and Apparent Temperature Variations |
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