Current Challenges in Gravitation and Cosmology
Post-doctoral Fellowship 2020
The Commission in charge of the evaluation of the candidates (composed by Profs. Maria Fatima Alves da Silva, Henrique Oliveira, and Rodrigo Maier) decided that the following ones can be considered for the position:
1- Pedro Mario Cañate Casseres.
2- Fulvio Sbisa.
3- Majid Abdollahi Zadeh.
4- Abolhassan Mohammadi.
5- Debabrata Deb.
6- Marcos Ramiro Alfredo Arcodia.
The fellowship has been awarded to the candidate in the first place of the list, Pedro Mario Cañate Casseres.
Research missions:
- Rodrigo Maier: 07/10/2019 – 18/10/2019, development of research topics in Cosmology, in collaboration with Prof. David Wands (University of Portsmouth-UK).
- Santiago Esteban Perez Bergliaffa: 07/10/2019 - 18/10/2019, collaboration with Prof. Luis Anchordoqui, Lehman College (New York), who is an expert in theory and observations of astrophysical phenomena, and their relation with Cosmology.
Seminars and Colloquia
Seminário: Massa Geométrica em Distribuições Esféricas e Cilíndricas Carregadas
Prof. Nilton O. Santos (Observatoire de Paris-Meudon )
15/10/2019, 13:20 hs, sala a confirmar.
Papapetrou e Majumdar (1947) obtiveram uma intrigante solução de poeira carregada eletricamente. Eles mostraram que se a densidade de massa for constante e igual à densidade de carga (em unidades geométricas), as equações de campo admitem solução estática. Este resultado que, aparentemente, viola o conceito de massa geométrica não foi devidamente estudado. Nesse seminário me proponho a desenvolver uma discussão sobre o assunto.
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Colóquio: Sistemas Cilíndricos em Relatividade Geral
Prof. Nilton O. Santos (Observatoire de Paris-Meudon )
23/10/2019, 11:00 hs. Auditório do Programa de Pós-graduação em Física.
Sistemas cilíndricos em Relatividade Geral (RG) foram muito estudados nos últimos anos. Estes geralmente estão relacionados a um número muito grande de diferentes situações físicas e astrofísicas, tais como sistemas em rotação/translação, colapso gravitacional, produção de ondas gravitacionais, jatos extragalácticos. entre outros. Por outro lado, esta simetria se mostra muito útil ao estudo da própria estrutura da teoria da RG e suas interpretações. Nesse colóquio abordarei alguns dos pontos que considero mais relevantes neste tema, dada a sua extensão.
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Open issues in the physics of relativistic jets
Prof. Gustavo Esteban Romero (Universidad nacional de La Plata, Argentina)
30/10/2019, 11:00 hs, Auditório do Programa de Pós-graduação em Física.
Relativistic jets are collimated outflows from accreting compact objects. They emit radiation from radio to gamma rays and possibly neutrinos. Jets on different scales are launched by accreting binaries, quasars and other active galactic nuclei, as well as by transient sources such as gamma-ray bursts. The physics of these jets is still not well-understood. In this talk I will discuss some open issues relative to their formation and content, and I will offer some possible solutions to such problems.
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Cosmological black holes
Dra. Daniela Pérez (Instituto Argentino de Radioastronomía, La Plata, Argentina)
05/11/2019, 13:20 hs, sala a confirmar.
There are exact solutions of Einstein field equations that describe how the cosmic expansion affects the dynamics of local systems. In the thirties, McVittie was the first to derive the spacetime metric that represents a central inhomogeneity embedded in a Friedmann - Lemaître - Robertson -Walker cosmological background. Generalizations of the McVittie metric were later obtained. These cosmological spacetimes, however, have not yet been completely characterize, let alone the associated geodetic motion. In the first part of the talk, I will present some novel calculations of the trajectories of photons and massive particles for these families of metrics that shed some light on their characterization and interpretation.
In the second part of the talk, I will show that cosmological black holes solutions can be extended to alternative theories of gravitation. In particular, I will introduce a new exact solution of Scalar- Tensor-Vector-Gravity that represents a black hole immersed in a cosmological background, analyze its corresponding properties, and compare with McVittie solution in General Relativity. I will close the presentation with some remarks on the direct astrophysical implications of the results here presented.