  Though widely accepted, it is not proven that supermassive compact objects
(SMCOs) residing in galactic centers are black holes. In particular, the Milky
Way's SMCO can be a giant nontopological soliton, Q-ball, made of a scalar
field: this fits perfectly all observational data. Similar but tiny Q-balls
produced in the early Universe may constitute, partly or fully, the dark
matter. This picture explains in a natural way, why our SMCO has very low
accretion rate and why the observed angular size of the corresponding radio
source is much smaller than expected. Interactions between dark-matter Q-balls
may explain how SMCOs were seeded in galaxies and resolve well-known problems
of standard (non-interacting) dark matter.
