Perturbations of Gravitational Systems: the Vaidya Metric, Mini Black Holes and Gravastars

Author(s)

Cecilia Bertoni Martha Hadler Chirenti

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2007-07-02

Examining board members

Elcio Abdalla; Luis Raul Weber Abramo; George Emanuel Avraam Matsas; Reuven Opher; Carlos Alexandre Wuensche de Souza

• Advisor: Elcio Abdalla

Abstract

Perturbative studies of gravitational systems in General Relativity have gone through big developments in the last years, especially due to the evolution of the modern gravitational wave detectors. We consider in this work different perturbations in different scenarios. Firstly we consider the Vaidya metric, mainly used to describe time-dependent spherically symmetric spacetimes. Our simulations show that the frequencies of the quasinormal modes (QNM\'s) present a new inertial effect for rapidly varying mass functions, returning afterwards to the adiabatic behavior. Next we present a model for evaporating mini black holes in particle accelerators, in the context of the new gravity models with extra dimensions. With our model, based on the n-dimensional Vaidya metric, we are able to perform a QNM analysis which results in the possibility of obtaining the parameters of the black hole, such as its initial mass and the number of extra dimensions, from the experimental measurements. Finally, we present a study of a new solution, the gravastar, proposed as an alternative model for the end state of massive stars. We obtain bounds for the parameters of the solution and verify its stability against axial perturbations. Our results indicate that the gravastar\'s QNM spectrum can indeed be used to distinguish a black hole from a gravastar. (AU)