  Fluids in external gravity may oscillate with frequencies characteristic of
the epicyclic motions of test particles. We explicitly demonstrate that global
oscillations of a slender, perfect fluid torus around a Kerr black hole admit
incompressible vertical and radial epicyclic modes. Our results may be directly
relevant to one of the most puzzling astrophysical phenomena -- high (hundreds
of hertz) frequency quasiperiodic oscillations (QPOs) detected in X-ray fluxes
from several black hole sources. Such QPOs are pairs of stable frequencies in
the 3/2 ratio. It seems that they originate a few gravitational radii away from
the black hole and thus observations of them have the potential to become an
accurate probe of super-strong gravity.
