The main objective of the thesis was to study the background of gravitational waves (GW) induced by scalar perturbations during the domination phase of inflation and radiation. Firstly it has been done a summary of inflation and the gravitational waves at first order induced by scalar by vaccum fluctuation of the metric tensor, then it has been provided the state of art of the gravitational waves induced by scalar at second order of cosmological perturbation during inflation and radiation domination. Subsequently inflationary model were studied which present specific features in the curvature power spectrum; infact a bump in this kind of scalar spectra induce in general, a specific features in the spectral density of GW. In particular the features presented can be described as condition of estrangement from the scale invariant power spectrum typical of the Slowroll inflation. In that situation is possible to describe a better comparability between the curvature power spectrum and the power spectrum of inflaton perturbation, so a better comparability between the spectral density of GWs induced during radiation and inflation, respectively. Specifically a model of fast roll inflation has been studied for which it was built a toy model in order to calculate analytically the spectral density of GWs during the two phases, with the purpose of specify the comparability of the two observables. The ultimate goal is to calculate the tensor to scalar ratio of the model and to allow a good comparison between the analytical theory with the result offer ed by a computational approach.
The main objective of the thesis was to study the background of gravitational waves (GW) induced by scalar perturbations during the domination phase of inflation and radiation. Firstly it has been done a summary of inflation and the gravitational waves at first order induced by scalar by vaccum fluctuation of the metric tensor, then it has been provided the state of art of the gravitational waves induced by scalar at second order of cosmological perturbation during inflation and radiation domination. Subsequently inflationary model were studied which present specific features in the curvature power spectrum; infact a bump in this kind of scalar spectra induce in general, a specific features in the spectral density of GW. In particular the features presented can be described as condition of estrangement from the scale invariant power spectrum typical of the Slowroll inflation. In that situation is possible to describe a better comparability between the curvature power spectrum and the power spectrum of inflaton perturbation, so a better comparability between the spectral density of GWs induced during radiation and inflation, respectively. Specifically a model of fast roll inflation has been studied for which it was built a toy model in order to calculate analytically the spectral density of GWs during the two phases, with the purpose of specify the comparability of the two observables. The ultimate goal is to calculate the tensor to scalar ratio of the model and to allow a good comparison between the analytical theory with the result offer ed by a computational approach.
Scalarinduced Gravitational Waves from Inflation
IANNICCARI, ANDREA
2022/2023
Abstract
The main objective of the thesis was to study the background of gravitational waves (GW) induced by scalar perturbations during the domination phase of inflation and radiation. Firstly it has been done a summary of inflation and the gravitational waves at first order induced by scalar by vaccum fluctuation of the metric tensor, then it has been provided the state of art of the gravitational waves induced by scalar at second order of cosmological perturbation during inflation and radiation domination. Subsequently inflationary model were studied which present specific features in the curvature power spectrum; infact a bump in this kind of scalar spectra induce in general, a specific features in the spectral density of GW. In particular the features presented can be described as condition of estrangement from the scale invariant power spectrum typical of the Slowroll inflation. In that situation is possible to describe a better comparability between the curvature power spectrum and the power spectrum of inflaton perturbation, so a better comparability between the spectral density of GWs induced during radiation and inflation, respectively. Specifically a model of fast roll inflation has been studied for which it was built a toy model in order to calculate analytically the spectral density of GWs during the two phases, with the purpose of specify the comparability of the two observables. The ultimate goal is to calculate the tensor to scalar ratio of the model and to allow a good comparison between the analytical theory with the result offer ed by a computational approach.File  Dimensione  Formato  

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https://hdl.handle.net/20.500.12608/45469