Zucchini, Sara
(2018)
Primordial black holes in string inflation.
[Laurea magistrale], Università di Bologna, Corso di Studio in
Fisica [LM-DM270]
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Abstract
In this thesis we consider the production of primordial black holes (PBH) in the context of single field inflation with the aim of describing a significant fraction of dark matter. In the models we consider, the inflaton is a string modulus and its potential is typical of type IIB fibre inflation. The potential presents a plateau at CMB scales and an extremely flat region on smaller scales. The background is analysed by solving the Friedmann's and the Klein-Gordon equations for the system. Perturbations are introduced through the usual Mukhanov-Sasaki equation for the gauge invariant curvature perturbations, whose solution allows us to find the primordial power spectrum which is then compared to observations. In the class of models considered there is an often occurring tension between the tilt of the scalar power spectrum and observations. We study this tension and propose mechanisms to minimise it. We modify the form of the fibre inflationary potential, modifying therefore the slope of the ultra slow-roll plateau. We find that a better agreement with the experimentally measured value of the spectral index can be reached. Therefore that tension between the value of the spectral index on CMB scale and the power spectrum enhancement on PBH scales can be explained as a consequence of the class of potential taken into account. This tension can be avoided in models that provide a different plateau form.
Abstract
In this thesis we consider the production of primordial black holes (PBH) in the context of single field inflation with the aim of describing a significant fraction of dark matter. In the models we consider, the inflaton is a string modulus and its potential is typical of type IIB fibre inflation. The potential presents a plateau at CMB scales and an extremely flat region on smaller scales. The background is analysed by solving the Friedmann's and the Klein-Gordon equations for the system. Perturbations are introduced through the usual Mukhanov-Sasaki equation for the gauge invariant curvature perturbations, whose solution allows us to find the primordial power spectrum which is then compared to observations. In the class of models considered there is an often occurring tension between the tilt of the scalar power spectrum and observations. We study this tension and propose mechanisms to minimise it. We modify the form of the fibre inflationary potential, modifying therefore the slope of the ultra slow-roll plateau. We find that a better agreement with the experimentally measured value of the spectral index can be reached. Therefore that tension between the value of the spectral index on CMB scale and the power spectrum enhancement on PBH scales can be explained as a consequence of the class of potential taken into account. This tension can be avoided in models that provide a different plateau form.
Tipologia del documento
Tesi di laurea
(Laurea magistrale)
Autore della tesi
Zucchini, Sara
Relatore della tesi
Scuola
Corso di studio
Indirizzo
Curriculum A: Teorico generale
Ordinamento Cds
DM270
Parole chiave
Primordial Black Holes,Dark Matter,String Inflation,Modified Fibre Inflation,Ultra slow-roll,Power Spectrum,Spectral Index,Curvature Perturbations
Data di discussione della Tesi
14 Dicembre 2018
URI
Altri metadati
Tipologia del documento
Tesi di laurea
(NON SPECIFICATO)
Autore della tesi
Zucchini, Sara
Relatore della tesi
Scuola
Corso di studio
Indirizzo
Curriculum A: Teorico generale
Ordinamento Cds
DM270
Parole chiave
Primordial Black Holes,Dark Matter,String Inflation,Modified Fibre Inflation,Ultra slow-roll,Power Spectrum,Spectral Index,Curvature Perturbations
Data di discussione della Tesi
14 Dicembre 2018
URI
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