The authors, David N. Spergel and Paul J. Steinhardt, propose that the discrepancies between cosmological models and observations of galaxy and cluster cores can be resolved by introducing self-interacting cold dark matter (DM) particles. They suggest that these particles have a large scattering cross-section but negligible annihilation or dissipation, with a mean free path of 1 kpc to 1 Mpc at the solar radius. This interaction can explain the observed spherical cores in galaxy clusters and the shallower density profiles of dwarf galaxies, which are inconsistent with the standard model of weakly interacting DM. The proposed interactions could be due to strong, short-range forces or weak interactions mediated by light particles. The authors also discuss the implications of these interactions for astrophysical processes, such as the evolution of dark matter halos and the dynamics of dwarf galaxies. They conclude that numerical simulations are needed to refine their estimates and verify their predictions, which include the spherical nature of halo centers, the presence of cores in dark matter halos, and the smaller radii of dwarf galaxy halos compared to gravitational tidal radii.The authors, David N. Spergel and Paul J. Steinhardt, propose that the discrepancies between cosmological models and observations of galaxy and cluster cores can be resolved by introducing self-interacting cold dark matter (DM) particles. They suggest that these particles have a large scattering cross-section but negligible annihilation or dissipation, with a mean free path of 1 kpc to 1 Mpc at the solar radius. This interaction can explain the observed spherical cores in galaxy clusters and the shallower density profiles of dwarf galaxies, which are inconsistent with the standard model of weakly interacting DM. The proposed interactions could be due to strong, short-range forces or weak interactions mediated by light particles. The authors also discuss the implications of these interactions for astrophysical processes, such as the evolution of dark matter halos and the dynamics of dwarf galaxies. They conclude that numerical simulations are needed to refine their estimates and verify their predictions, which include the spherical nature of halo centers, the presence of cores in dark matter halos, and the smaller radii of dwarf galaxy halos compared to gravitational tidal radii.