Theory of Dark Matter

We discuss the hypothesis that the constituents of dark matter in the galactic halo are primordial intermediate-mass black holes (PIMBHs). The status of axions and weakly interacting massive particles (WIMPs) is discussed, as are the methods for detecting PIMBHs with emphasis on microlensing. The role of the angular momentum $\mathcal{J}$ of the PIMBHs in their escaping previous detection is considered.