Growth of cosmological structures in an interacting vacuum scenario

Sebastianutti, Marco (2022) Growth of cosmological structures in an interacting vacuum scenario. [Laurea magistrale], Università di Bologna, Corso di Studio in Physics [LM-DM270]
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Abstract

The widely accepted standard model of cosmology consists of a cosmological constant, Λ, responsible for the present expansion of the Universe, and cold dark matter, (CDM), accountable for structure formation. This famous model, also known as ΛCDM, suffers from both theoretical and observational problems, which motivate the study of alternative models. In this thesis I present an alternative scenario: the interacting vacuum. In this class of models, unlike in ΛCDM, vacuum energy, a dark energy with w = −1 equation of state, and CDM are allowed to exchange energy and momentum. I focus, in particular, on the geodesic CDM case, where only a pure energy exchange is allowed. Within this subclass, three relevant models are considered: the linear vacuum model, whose energy exchange is proportional to the vacuum energy density, the generalised Chaplygin gas (GCG) interacting model, obtained decomposing the original GCG into the two interacting dark components, and the Shan-Chen (SC) interacting model obtained as well from a decomposition of the original SC model. The aim of this elaborate is, using the covariant gauge-invariant (CGI) theory of cosmological perturbations, to show, for the aforementioned models, how the vacuum-CDM interaction affects the growth of cosmic structures. It is found that a growing/decaying vacuum energy always leads, for fixed initial conditions, to a less/more decreasing growth rate f w.r.t. the non-interacting limit, namely the ΛCDM model.

Abstract
Tipologia del documento
Tesi di laurea (Laurea magistrale)
Autore della tesi
Sebastianutti, Marco
Relatore della tesi
Correlatore della tesi
Scuola
Corso di studio
Indirizzo
THEORETICAL PHYSICS
Ordinamento Cds
DM270
Parole chiave
Cosmological perturbation theory,Covariant gauge invariant cosmological perturbation theory,Linear vacuum model,Generalised Chaplygin gas interacting model,Shan Chen interacting model,Vacuum perturbations,Bardeen formalism,Ellis Bruni formalism
Data di discussione della Tesi
25 Marzo 2022
URI

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