Haloes, other dark matter candidates and astrophysical implications

It is possible that a multi-component dark matter model is required if primordial black holes only contribute to a fraction of the energy density in dark matter. This is increasingly more likely with respect to the case of $f_{\rm PBH} = 1$, since there is only one remaining window, on asteroid-mass scales, where primordial black holes can make up all of the dark matter. A mixed dark matter model can lead to interesting observables that come about due to the interactions between primordial black holes and the second dark matter component. This can provide unique signatures of the presence of primordial black holes and increase the prospects of detection or improvement of constraints in the mass ranges where $f_{\rm PBH} < 1$, whilst simultaneously exploring the remaining open parameter space for other dark matter candidates.