Dark matter with ultra compact mini halos

The isocurvature mode of dark matter is not damped away during kinetic decoupling from the thermal plasma. For weakly interaction massive particle as dark matter, the large density perturbation can generate the small scale ultra compact mini halos and the annihilation of dark matter inside them can give accessible signatures in the indirect detection of dark matter. The early matter domination epoch is one way to produce the isocurvature perturbation of weakly interacting massive dark matter at small scales from the initial adiabatic perturbation form single inflation model.