Résumé |
We use the near-horizon conformal symmetry of the extreme Kerr metric to determine universal properties of physics near rapidly spinning black holes. This constitutes an example of critical behavior in astronomy. We show how the symmetry accounts for two well-known effects, the tendency to expel magnetic flux (black hole Meissner effect) and the possibility of arbitrarily high-energy collisions (BSW effect). We also find the near-horizon form for diffuse (force-free) plasma and show that plasma particles are infinitely boosted relative to cold accretion flow. Active galactic nuclei powered by rapidly spinning black holes are therefore natural sites for high energy collisions. |