Ergoregion instability in rotating gravastars

@article{Chirenti2008ErgoregionII,
  title={Ergoregion instability in rotating gravastars},
  author={Cecilia Chirenti and Luciano Rezzolla},
  journal={Physical Review D},
  year={2008},
  volume={78},
  pages={084011}
}
The ergoregion instability is known to affect very compact objects that rotate very rapidly and do not possess a horizon. We present here a detailed analysis on the relevance of the ergoregion instability for the viability of gravastars. Expanding on some recent results, we show that not all rotating gravastars are unstable. Rather, stable models can be constructed also with J/M{sup 2}{approx}1, where J and M are the angular momentum and mass of the gravastar, respectively. The genesis of… 

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