Superdense cosmological dark matter clumps
  The formation and evolution of superdense clumps (or subhalos) is studied.
Such clumps of dark matter (DM) can be produced by many mechanisms, most
notably by spiky features in the spectrum of inflationary perturbations and by
cosmological phase transitions. Being produced very early during the radiation
dominated epoch, superdense clumps evolve as isolated objects. They do not
belong to hierarchical structures for a long time after production, and
therefore they are not destroyed by tidal interactions during the formation of
larger structures. For DM particles with masses close to the electroweak (EW)
mass scale, superdense clumps evolve towards a power-law density profile
$\rho(r) \propto r^{-1.8}$ with a central core. Superdense clumps cannot be
composed of standard neutralinos, since their annihilations would overproduce
the diffuse gamma radiation. If the clumps are constituted of superheavy DM
particles and develop a sufficiently large central density, the evolution of
their central part can lead to a 'gravithermal catastrophe.' In such a case,
the initial density profile turns into an isothermal profile with $\rho \propto
r^{-2}$ and a new, much smaller core in the center. Superdense clumps can be
bserved by gamma radiation from DM annihilations and by gravitational wave
detectors, while the production of primordial black holes and cascade
nucleosynthesis constrain this scenario.
