Dynamical constraints on dark compact objects

Many of the baryons in the Universe are dark and at least some of the dark baryons could be in the form of compact objects. Such objects could be in v arious locations - galactic discs, galactic halos, clusters of galaxies or intergalactic space - and each of these is associated with a dark matter pr oblem. For each site we consider the various dynamical constraints which ca n be placed on the fraction of the dark matter in compact objects of differ ent mass. We also apply these limits to the situation in which the compact objects are clusters of smaller objects. (C) 1998 Published by Elsevier Sci ence B.V. All rights reserved.