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Title: Cosmological perturbations from hilltop potentials
Author: Orani, Stefano
ISNI:       0000 0004 2742 0179
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Cosmological inflation is the dominating paradigm to account for observations of the Cosmic Microwave Background (CMB). In this thesis, we study the phenomenology of a class of particularly well motivated models of inflation, known under the generic name of hybrid models. They are characterised by a transition from a valley to a hilltop shaped potential. In particular, we study three limiting regimes of the simplest realisation, hybrid inflation, constraining its parameter space using observational bounds on the spectral index and the non-gaussianity of the primordial perturbations. We find that the model is highly constrained by observations, with large part of the parameter space either ruled out by a blue spectral index (ns > 1) or by a large non-gaussianity parameter fNL, two quantities measured with precision by PLANCK. However, there exists regions in parameter space leading to interesting phenomenology compatibly with observational bounds. Also, a version of hybrid inflation with a third light scalar field at horizon crossing is derived from the supersymmetry framework. We find that the model can generate observables within observational bounds.
Supervisor: Rajantie, Arttu Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral