  The nonbaryonic dark matter of the Universe is assumed to consist of new
stable forms of matter. Their stability reflects symmetry of micro world and
mechanisms of its symmetry breaking. In the early Universe heavy metastable
particles can dominate, leaving primordial black holes (PBHs) after their
decay, as well as the structure of particle symmetry breaking gives rise to
cosmological phase transitions, from which massive black holes and/or their
clusters can originate. PBHs can be formed in such transitions within a narrow
interval of masses about $10^{17}$g and, avoiding severe observational
constraints on PBHs, can be a candidate for the dominant form of dark matter.
PBHs in this range of mass can give solution of the problem of reionization in
the Universe at the redshift $z\sim 5... 10$. Clusters of massive PBHs can
serve as a nonlinear seeds for galaxy formation, while PBHs evaporating in such
clusters can provide an interesting interpretation for the observations of
point-like gamma-ray sources. Analysis of possible PBH signatures represents a
universal probe for super-high energy physics in the early Universe in studies
of indirect effects of the dark matter.
