  The collisionless cold dark matter (CCDM) model predicts overly dense cores
in dark matter halos and overly abundant subhalos. We show that the idea that
CDM are decaying superheavy particles which produce ultra-high energy cosmic
rays with energies beyond the Greisen-Zatsepin-Kuzmin cutoff may simultaneously
solve the problem of subgalactic structure formation in CCDM model. In
particular, the Kuzmin-Rubakov's decaying superheavy CDM model may give an
explanation to the smallness of the cosmological constant and a new thought to
the CDM experimental search.
