The past few years have seen a great deal of counterintuitive features in the kinematics around rotating black holes, and now a new effect could help explain the origin of the highest energy cosmic rays. Bahram Mashhoon and Carmen Chicone of the University of Missouri found that near a rotating black hole particles beyond a critical speed of c/√2 can experience huge accelerations perpendicular to the axis of rotation, which could be sufficient to produce particles carrying enough energy to be near the Greisen-Zatzepin-Kuzmin cut-off, above which no cosmic rays should be able to arrive from far away. New data expected from the Pierre Auger Observatory are eagerly awaited to see if there is any association of the highest energy cosmic rays with "microquasars" - X-ray binary systems that include black holes, which have been observed to emit high-energy jets of material.

Further reading

http://xxx.lanl.gov/abs/astro-ph/0406005.