Environment-dependent dark sector

We propose a new framework unifying cold dark matter (CDM) and modified Newtonian dynamics (MOND) to solve their respective problems on galactic scales and large scale structure formation. In our framework the dark matter clusters on large scales but not on galactic scales. This environment dependence of the dark matter behaviors is controlled by a vector field, which also produces the MOND effects in galaxies. We find that in this framework only a single mass scale needs to be introduced to produce the phenomena of CDM, MOND, and also dark energy.