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**Dr. Cecilia Chirenti**

Center for Mathematics, Computation and Cognition of UFABC (the Federal University of the ABC Region in the metropolitan area of São Paulo), in Brazil

August 29, 3:40 PM

Thirkield Hall (Physics), room 103

Gravastars: viable black hole
alternatives?

Gravastars have been proposed as one of the most fashionable alternatives to black holes. These hypothetical and very exotic objects would be in almost all aspects identical to black holes from the point of view of an external observer. They are equilibrium solutions of the Einstein field equations that have neither event horizons nor central singularities, and yet their surfaces can be infinitesimally close to (although still outside) their Schwarzschild radii. A complete theory of quantum gravity would be needed to fully explain the mechanism behind the formation of a gravastar: a phase transition during the collapse of a massive star leading to the formation of a gravitational Bose-Einstein condensate that would stop the collapse and stabilize the solution. I will present some of the properties of these solutions, the many tests that they have already been through to probe their viability, and the strict new tests posed by the LIGO gravitational wave observations.

Cecilia Chirenti is an associate professor at the Center for Mathematics, Computation and Cognition of UFABC (the Federal University of the ABC Region in the metropolitan area of São Paulo), in Brazil. She obtained her PhD in Physics from the University of São Paulo in 2007, and had a Humboldt Fellowship during her postdoctoral assignment at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Potsdam, Germany, from 2007 to 2009, when she returned to Brazil to start working at UFABC. Her research focuses on the study of small perturbations of compact astrophysical objects, such as black holes and neutron stars. The recent detections of gravitational waves are helping to bridge the gap between her work on mathematical aspects of general relativity and astrophysical observations. She currently has collaborations with the Universities of Maryland, Frankfurt and Tokyo.

**Refreshments will be served
****at 3:30pm**