Defense
Student: Pablo William Rodrigues de Lima
Program: Astronomia
Title: "Nonstandard Cosmologies With Gravitationally Induced Particle Creation"
Advisor: Prof. Dr. José Ademir Sales de Lima - IAG/USP
Judging Comitee:
- Prof. Dr. José Ademir Sales de Lima – Presidente e Orientador – IAG/USP
- Prof. Dr. Reinaldo dos Santos Lima – IAG/USP
- Prof. Dr. Airton Deppman – IF/USP
- Prof. Dr. José Fernando de Jesus – UNESP (por videoconferência)
- Prof. Dr. Luiz Cleber Tavares de Brito – UFLA (por videoconferência)
- Prof. Dr. Vilson Zanchin – UFABC
Other Members:
- Prof. Dr. Eduardo Serra Cypriano - IAG/USP
- Prof. Dr. Valdir Barbosa Bezerra – UFPB (por videoconferência)
- Prof. Dr. Márcio Roberto de Garcia Maia – UFSBA (por videoconferência)
- Prof. Dr. Carlos Molina Mendes – EACH/USP (por videoconferência)
- Prof. Dr. João Vital da Cunha Jr – UFRN (por videoconferência)
- Prof Dr. Janilo Santos – UFRN (por videoconferência)
Abstract:
As alternatives to the standard cosmological scenario (ΛCDM), that has faced theoretical and observational problems to describe the observed universe, we investigate two models in which particles are created from gravitational effects. In this context, a negative pressure generated by the irreversible process of particle creation, induced by cosmic expansion, is capable of accelerating the universe without any exotic fluids, such as dark energy. In the first model, we consider the universe to be predominantly composed of a reduced relativistic gas. Such formulation accounts for the relativistic contributions of massive particles to cosmic dynamics, addressed within the framework of the so-called reduced gas approximation. In the second model, we present a cosmological scenario, classically complete, in which the radiation and matter eras are also modified by particle creation. In both cases, the resultant dynamics is slightly different from the predictions of the ΛCDM model. Both in the background and perturbative levels, we argue that these small modifications might offer promising ways of solving the current cosmological tensions. To estimate the parameters and test the viability of these scenarios, we provide detailed statistical analyses using observational data from type Ia supernovae, H(z) measurements from cosmic chronometers and redshift-space distortion based fσ8 data.
Palavras-chave: Cosmology, Particle Creation, Relativistic Gas