The current evidence of an accelerated expansion of the universe is briefly discussed from an historical perspective and in the context of general relativity, the concept of dark energy is introduced. The presence of extra mass which doesn’t interact electromagnetically, called dark matter, is also shortly adressed. Given the fluid equation describing the evolution of the energy density ρ of the universe for FLRW models, a barotropic nonlinear equation of state (EoS) P(ρ) is chosen, specifically the quadratic form P(ρ) = P0 + αρ + βρ2, already discussed by Ananda and Bruni in [1]. This particular form serves as a general approximation for every P(ρ), as it is the Taylor expansion up to the second order about ρ = 0. The EoS is studied in the high and low energy regimes and ultimately the full EoS is considered. The cosmological behaviours are discussed and compared. In detail, the change in the free parameters is explored in its consequences on closed, open and flat geometrical models of spacetime, standard and phantom behaviours are found along with different possibilities for future/past singularities. The whole analysis is done using the theory of dynamical systems.
The current evidence of an accelerated expansion of the universe is briefly discussed from an historical perspective and in the context of general relativity, the concept of dark energy is introduced. The presence of extra mass which doesn’t interact electromagnetically, called dark matter, is also shortly adressed. Given the fluid equation describing the evolution of the energy density ρ of the universe for FLRW models, a barotropic nonlinear equation of state (EoS) P(ρ) is chosen, specifically the quadratic form P(ρ) = P0 + αρ + βρ2, already discussed by Ananda and Bruni in [1]. This particular form serves as a general approximation for every P(ρ), as it is the Taylor expansion up to the second order about ρ = 0. The EoS is studied in the high and low energy regimes and ultimately the full EoS is considered. The cosmological behaviours are discussed and compared. In detail, the change in the free parameters is explored in its consequences on closed, open and flat geometrical models of spacetime, standard and phantom behaviours are found along with different possibilities for future/past singularities. The whole analysis is done using the theory of dynamical systems.
Cosmological dynamics of "Unified Dark Matter" models based on perfect fluids Dinamica cosmologica di modelli di "Unified Dark Matter" basati su fluidi perfetti
TRENTIN, RENATO
2021/2022
Abstract
The current evidence of an accelerated expansion of the universe is briefly discussed from an historical perspective and in the context of general relativity, the concept of dark energy is introduced. The presence of extra mass which doesn’t interact electromagnetically, called dark matter, is also shortly adressed. Given the fluid equation describing the evolution of the energy density ρ of the universe for FLRW models, a barotropic nonlinear equation of state (EoS) P(ρ) is chosen, specifically the quadratic form P(ρ) = P0 + αρ + βρ2, already discussed by Ananda and Bruni in [1]. This particular form serves as a general approximation for every P(ρ), as it is the Taylor expansion up to the second order about ρ = 0. The EoS is studied in the high and low energy regimes and ultimately the full EoS is considered. The cosmological behaviours are discussed and compared. In detail, the change in the free parameters is explored in its consequences on closed, open and flat geometrical models of spacetime, standard and phantom behaviours are found along with different possibilities for future/past singularities. The whole analysis is done using the theory of dynamical systems.File  Dimensione  Formato  

Trentin_Renato.pdf
accesso aperto
Dimensione
3.73 MB
Formato
Adobe PDF

3.73 MB  Adobe PDF  Visualizza/Apri 
The text of this website © Università degli studi di Padova. Full Text are published under a nonexclusive license. Metadata are under a CC0 License
https://hdl.handle.net/20.500.12608/41600