Radiative Corrections in Curved Spacetime and Physical Implications to the Power Spectrum and Trispectrum for different Inflationary Models
von Simone Dresti
Datum der mündl. Prüfung:2018-05-23
Erschienen:2018-06-26
Betreuer:Prof. Dr. Laura Covi
Gutachter:Prof. Dr. Laura Covi
Gutachter:Prof. Dr. Dorothea Bahns
Dateien
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Zusammenfassung
Englisch
In a quantum field theory with a time-dependent background, as in an expanding universe, the time-translational symmetry is broken. We therefore expect loop corrections to cosmological observables to be time-dependent after renormalization for interacting fields. In this thesis we compute and discuss such radiative corrections to the primordial spectrum and higher order spectra in simple inflationary models. We investigate both massless and massive virtual fields, and we disentangle the time dependence caused by the background and by the initial state that is set to the Bunch-Davies vacuum at the beginning of inflation. For the investigated models, we find that the radiative corrections to the primordial spectrum result in oscillatory features that are not present at tree-level. These features are also present in higher order spectra and depend on the initial conditions of the theory. In all the investigated cases the departure from near-scale invariance and from Gaussianity is very small and it is in full agreement with the current Planck constraints. Future cosmic microwave background measurements may improve the current limits on feature-full primordial spectra, giving the hope to observe these effects in the scenario of hybrid inflation.
Keywords: Primordial Power Spectrum; Trispectrum; Inflationary Perturbations; Inflaton Field; Slow-Roll Inflation; Hybrid Inflation; Chaotic Inflation; Non-Linearity Parameter; De-Sitter Spacetime; Renormalization in Curved Spacetime; Radiative Corrections; Finite Time Contributions; CTP Formalism; WKB Propagator; Hypergeometric Propagator