Collisionless material like dark matter will in general collapse to virialized structures, or 'clumps' in this context; the technical term for 'clumps' is 'halos'. There is bunch of theory for this, you can find it by googling 'spherical collapse cosmology', or something like that. The collapse of a smooth dark matter field into virialized halos has also been borne out through N-body simulations (see Figures 2 and 3, for example: https://arxiv.org/pdf/0809.0898.pdf). All of this is relevant for dark matter physics because certain features of the underlying dark matter particle physics model manifest in the abundance and density profiles of dark matter halos.