This paper concerns closed hypersurfaces of dimension n(≥2) in the
hyperbolic space Hκn+1 of constant sectional curvature
κ evolving in direction of its normal vector, where the speed is given
by a power β(≥1/m) of the mth mean curvature plus a volume
preserving term, including the case of powers of the mean curvature and of the
\mbox{Gau\ss} curvature. The main result is that if the initial hypersurface
satisfies that the ratio of the biggest and smallest principal curvature is
close enough to 1 everywhere, depending only on n, m, β and κ,
then under the flow this is maintained, there exists a unique, smooth solution
of the flow for all times, and the evolving hypersurfaces exponentially
converge to a geodesic sphere of Hκn+1, enclosing the
same volume as the initial hypersurface.Comment: 36page