Full text
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| Author(s): |
Lucas Collis Olivari
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física (IF/SBI) |
| Defense date: | 2014-05-14 |
| Examining board members: |
Elcio Abdalla;
Luis Raul Weber Abramo;
Vilson Tonin Zanchin
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| Advisor: | Elcio Abdalla |
| Abstract | |
In this work we studied cosmological models in which the dark energy was treated as a field of matter that interacts with dark matter. Three different models were considered. The first one treats both the cold dark matter and the dark energy as perfect fluids. The interaction term between them is given by a expression with phenomenological origin that we postulated to exist in the balance equations between these two fluids. Given the equations in the flat Friedmann-Robertson-Walker (FRW) universe, we wrote a covariant version of the balance equations. Thus, the balance equations in a linearly perturbed FRW universe were obtained. This, in turn, allowed the stability of the obtained differential equations to be studied. The second model comes from f(R) models. These models propose a generalization of General Relativity by considering the action for gravity as a functional of the Ricci scalar, R. Through a conformal transformation, it was possible to reinterpret the f(R) models as models in which a canonical scalar field, which represents the dark energy, interacts with matter fields. Through the principle of least action, we obtained the equations of motion and the energy-momentum tensor for our system. With the scalar field being interpreted as a perfect fluid, we obtained equations of balance for perfect fluids at both the background level and in the linearly perturbed universe. The third model starts with the Lagrangian, in a FRW space-time, of a canonical scalar field, which represents the dark energy, and of a fermionic field of spin-1/2, which represents the dark matter. A Yukawa interaction term between these fields was postulated to exist in the Lagrangian. Again, through the principle of least action, we obtained the equations of motion and the energy-momentum tensor for these fields. These equations of motion could then be rewritten as balance equations for perfect fluids at both the background level and in the linearly perturbed universe. (AU) | |
| FAPESP's process: | 11/15463-0 - Influence of energy-momentum transfer in the interaction between matter and dark energy |
| Grantee: | Lucas Collis Olivari |
| Support Opportunities: | Scholarships in Brazil - Master |