Unit:
Department of PhysicsLibrary of the School of Science
Author:
Kontaxis Georgios
Dissertation committee:
Νικόλαος Τετράδης (Επιβλέπων) - Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ
Φώτιος Διάκονος - Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ
Γεώργιος Διαμάντης - Αναπληρωτής Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ
Αλέξανδρος Κεχαγιάς - Καθηγητής, ΣΕΜΦΕ, ΕΜΠ
Χριστόφορος Κούβαρης - Καθηγητής, ΣΕΜΦΕ, ΕΜΠ
Κωνσταντίνος Σφέτσος - Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ
Βασίλειος Σπανός - Αναπληρωτής Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ
Original Title:
Amplification and Oscillations in the Curvature Power Spectrum from Features in the Inflaton Potential
Translated title:
Amplification and Oscillations in the Curvature Power Spectrum from Features in the Inflaton Potential
Summary:
In this thesis we study features of the inflaton potential that can lead to a strong enhancement of the power spectrum of curvature perturbations. In single-field inflation, which constitutes the biggest part of this work, we focus on models with steep step-like features in the potential that result in the temporary violation of the slow-roll conditions during the inflaton evolution. These features enhance the power spectrum of the curvature perturbations by several orders of magnitude at certain scales and also produce prominent oscillatory patterns. Our analysis regarding the inflationary dynamics is both analytical and numerical. We describe quantitatively the size of the enhancement, as well as the profile of the oscillations, which are shaped by the number and position of the features in the potential. The models that we use include some simplified potentials, as well as potentials that are constructed within the framework of $\alpha$-attractors in supergravity. We also demonstrate that the induced tensor power spectrum inherits the distinctive oscillatory profile of the curvature spectrum and is potentially detectable by near-future space interferometers. In addition, the enhancement of the power spectrum by several step-like features may trigger the production of a sizeable number of primordial black holes under suitable conditions.
We also extend our work on the enhancement of the curvature spectrum during inflation to the two-fi eld case. Our emphasis here is given on sharp turns in field space, which is a clearly multi- field phenomenon that occurs when the component of the slow-roll parameter perpendicular to the background trajectory grows large. Our focus is mainly on the additive e effect of several turns, leading to the resonant growth of the curvature spectrum. Three or four features in the evolution of η are sufficient in order to induce
an enhancement of the power spectrum by six or seven orders of magnitude, which can lead to the signifi cant production of primordial black holes and stochastic gravitational waves, in analogy with the case of steps in the potential.
Main subject category:
Science
Keywords:
inflation, curvature perturbations, power spectrum, step-like features, turns in eld space, primordial black holes, induced gravitational waves
Number of references:
196
