Alessandrini, Federico
(2023)

*Explicit inflationary models for the enhancement of
primordial fluctuations.*
[Laurea magistrale], Università di Bologna, Corso di Studio in

Physics [LM-DM270]

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## Abstract

The nature of dark matter remains one of the fundamental quests of modern physics. One of its
simplest explanations is based on the assumption that a large amount of DM is made of black
holes of primordial origin (PBHs). Such an explanation is compelling since it does not rely on the
existence of new particles or some modification of the gravitational interaction. PBHs can form
from the collapse of large density perturbations in the early universe, that could have formed from
the inflaton fluctuations. An amplification of these fluctuations of several orders of magnitude with
respect to those probed by Cosmic Microwave Background (CMB) radiation is necessary to trigger
the collapse. In this work, two different scenarios of amplification are studied. First, we analyze
the case of a minimally coupled inflaton. The reconstruction of a class of potentials leading to an
amplification is discussed and then we study the resulting spectrum and the dynamical features of
the amplification for different potentials. The same study is then employed for the more general
scenario of a non-minimally coupled inflaton, restricting the analysis, for simplicity, to the induced
gravity case. In this context, we used the superpotential method to reconstruct the form of a
potential leading to a spectrum amplification. In both cases, we build complete models of inflation
that account for the constraints of CMB observations at larger scales and the requirements for PBH
production at smaller scales. Finally, we compared the models analyzed to some of the recent PTA
datasets analysis and we obtained that some inflationary models are mildly favoured w.r.t. others
in fitting the constraints for the production of SIGW.

Abstract

The nature of dark matter remains one of the fundamental quests of modern physics. One of its
simplest explanations is based on the assumption that a large amount of DM is made of black
holes of primordial origin (PBHs). Such an explanation is compelling since it does not rely on the
existence of new particles or some modification of the gravitational interaction. PBHs can form
from the collapse of large density perturbations in the early universe, that could have formed from
the inflaton fluctuations. An amplification of these fluctuations of several orders of magnitude with
respect to those probed by Cosmic Microwave Background (CMB) radiation is necessary to trigger
the collapse. In this work, two different scenarios of amplification are studied. First, we analyze
the case of a minimally coupled inflaton. The reconstruction of a class of potentials leading to an
amplification is discussed and then we study the resulting spectrum and the dynamical features of
the amplification for different potentials. The same study is then employed for the more general
scenario of a non-minimally coupled inflaton, restricting the analysis, for simplicity, to the induced
gravity case. In this context, we used the superpotential method to reconstruct the form of a
potential leading to a spectrum amplification. In both cases, we build complete models of inflation
that account for the constraints of CMB observations at larger scales and the requirements for PBH
production at smaller scales. Finally, we compared the models analyzed to some of the recent PTA
datasets analysis and we obtained that some inflationary models are mildly favoured w.r.t. others
in fitting the constraints for the production of SIGW.

Tipologia del documento

Tesi di laurea
(Laurea magistrale)

Autore della tesi

Alessandrini, Federico

Relatore della tesi

Correlatore della tesi

Scuola

Corso di studio

Indirizzo

THEORETICAL PHYSICS

Ordinamento Cds

DM270

Parole chiave

Cosmology,Inflation,Primordial Black Holes,Quantum Cosmology

Data di discussione della Tesi

15 Dicembre 2023

URI

## Altri metadati

Tipologia del documento

Tesi di laurea
(NON SPECIFICATO)

Autore della tesi

Alessandrini, Federico

Relatore della tesi

Correlatore della tesi

Scuola

Corso di studio

Indirizzo

THEORETICAL PHYSICS

Ordinamento Cds

DM270

Parole chiave

Cosmology,Inflation,Primordial Black Holes,Quantum Cosmology

Data di discussione della Tesi

15 Dicembre 2023

URI

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