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Energy Extraction from Black Holes: Advances and Challenges in BH Physics

Explore the latest research on energy extraction from black holes at the BHs 2011 conference in Aveiro, Portugal. Learn about the slingshot effect, tidal acceleration, ergo-region instability, and more. Discover implications for gravitational theories and the potential of resonant excitation of BH modes. Dive into the unstable nature of Kerr-AdS BHs, ergoregion rules, and the relevance of massive scalar fields. Floating orbits and gravitational wave spectrum encodings are also discussed. Stay updated on the latest developments in BH physics from leading researchers like Cardoso, Pani, and Yunes.

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Energy Extraction from Black Holes: Advances and Challenges in BH Physics

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  1. Energyextractionfromblackholes BHs2011 19-20 Dec 2011 | Aveiro, Portugal Credit: ESO/MPE (2010) Vitor Cardoso (CENTRA/IST & Olemiss)

  2. Credit: ESO/MPE/M.Schartmann (2011)

  3. Orbital energy: slingshoteffect

  4. Rotational energy: tidal acceleration

  5. Tidalaccelerationisin general impossible for BHs! Press & Teukolsky, Nature (1973)

  6. Ergo-region: asymptotictime-translationKiling vector isspace-like Penrose process • Superradiance • Hawking radiation

  7. Insert a mirroraroundthe BH anti-de Sitter Make a “bomb”! (Zel’dovich, 1971; Press & Teukolsky 1973) SmallKerr-AdSBHs are unstable (Cardoso & Dias ‘04; Kodama ’07; Uchikata, Yoshida & Futamase ’09)

  8. (Witeketal, ‘10)

  9. Horizonless geometries? Theorem(Friedman, 1978): Everystationary, AF, horizonlessspacetimewithanergoregionisunstable (Intuition: negative-energystates are amplified, no horizon to absorbthem) Gravastars(Mazur & Mottola ‘01) BosonStars(Kaup ’68; Ruffini & Bonazzola ‘69) Wormholes(Morris & Thorne ‘88) Superspinars(Gimon & Horava ‘09) Ergoregioninstability rules out “all” of these! (Cardoso etal, ’08; Panietal ‘10;)

  10. Resonant excitation of BH modes? Resonant tides? MasslessmodesofBHs are localizedaroundthelightring... ...andthenullgeodesicliesinsidethe ISCO

  11. (massive) scalar fields Interesting as effective description Proxy for more complex interactions Arise as interesting alternatives of GR Brans-Dicke or generic scalar-tensor theories; quadratic f(R) GW spectrum encodes the gravity theory Axiverse scenarios (moduli and coupling constants in QCD, Peccei-Quinn mechanism QCD, etc)

  12. Massivefields MassivefieldsaroundKerr are unstable (Damouretal ‘76; Detweiler, ’80; Cardoso & Yoshida ’05; Dolan ‘07)

  13. Floatingorbits Cardoso et al, PRL107:241101, 2011

  14. Tidalaccelerationisequivalent to superradiancein BH physics •  • Inabsenceofotherdissipationmechanisms, tidaldissipationleads to floatingorbits •  • Floating orbits can be instrumental to constrain or prove existence of massive scalars coupled to matter... stilla lot to do

  15. Thank you Cardoso, Chakrabarti, Pani, Berti, Gualtieri, PRL107: 241101 (2011) Yunes, Pani, Cardoso, arXiv:1112.3351 • Cardoso, Pani, in progress (2012) ____________________________ ____________________________ 

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