Revealing the Structure of the Inflationary Landscape through Primordial non-Gaussianity

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Tesis MagísterAuthor
Scheihing Hitschfeld, Bruno SebastianAbstract
In this thesis, we show how the structure of the landscape potential of the primordial Uni- verse may be probed through the properties of the primordial density perturbations responsible for the origin of the cosmic microwave background anisotropies and the large-scale structure of our Universe. Isocurvature fields —fields orthogonal to the inflationary trajectory— may have fluctuated across the barriers separating local minima of the landscape p...
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In this thesis, we show how the structure of the landscape potential of the primordial Uni- verse may be probed through the properties of the primordial density perturbations responsible for the origin of the cosmic microwave background anisotropies and the large-scale structure of our Universe. Isocurvature fields —fields orthogonal to the inflationary trajectory— may have fluctuated across the barriers separating local minima of the landscape potential during inflation. We analyze how this process could have impacted the evolution of the primordial curvature perturbations. If the typical distance separating consecutive minima of the landscape potential and the height of the potential barriers are smaller than the Hubble expansion rate parametrizing inflation, the probability distribution function of isocurvature fields becomes non-Gaussian due to the appearance of bumps and dips associated with the structure of the potential. We show that this non-Gaussianity can be transferred to the statistics of primordial curvature perturbations if the isocurvature fields are coupled to the curvature perturbations. The type of non-Gaussian structure that emerges in the distribution of curvature perturbations cannot be fully probed with the standard methods of polyspectra; instead, the probability distribution function is needed. The latter is obtained by summing all the n-point correlation functions, which are of the local type.
To substantiate our claims, we offer a concrete model consisting of an axionlike isocurvature perturbation with a sinusoidal potential and a linear derivative coupling between the isocurvature and curvature field. This result is generalized to arbitrary potentials, studied beyond first-order perturbation theory, and extended to a more general class of backgrounds. We also briefly explore connections with the stochastic inflation framework. Finally, we undertake a study of primordial non-Gaussianity of the local type, where we use our results to reconstruct and constrain the shape of the landscape potential with the help of Cosmic Microwave Background observations by the Planck telescope, and additionally, we explore prospects for observable quantities in the Large-Scale Structure of our universe towards con- straining the primordial statistics of the universe.
Should any of these signals be measured by upcoming cosmological surveys, we will have our understanding of early-universe physics greatly enhanced, as those observations may be readily connected to the dynamics of the inflationary perturbations.
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Date de publicación
2019Academic guide
Palma Quilodran, Gonzalo Alejandro
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