| Abstract: | Macroscopic Dark Matter (DM), in particular Primordial Black Holes (PBH) and the Dark Matter miniclusters are well established dark matter candidates. I will briefly motivate these scenarios and present the current observational constraints on these ideas. I will further explain why the constrains on macroscopic dark with masses below 10^22 gram are so weak and discuss several ideas that can potentially improve the reach is this region of parameter space. In particular, I will concentrate on the femtolensing of the gamma ray bursts (GRBs) that has been put forward as an exciting idea to probe the exotic astrophysical objects with masses below 10^19 gram. I will critically review this idea, properly taking into account the extended nature of of the source as well as wave optics effects. These effects remove the previously claimed femtolensing bounds on the primordial black holes, implying that vast regions of the parameter space are not robustly constrained. I will further entertain the possibility that a small fraction of GRBs with short time variability can still be useful, however large number of such bursts will be needed to be observed to achieve meaningful constraints. I will present the sensitivity study of future observations. I will also briefly discuss some other ideas that can be used to probe the challenging regime of macroscopic DM with masses below 10^22 gram, including the observations of White Dwarfs, neutron stars , picolensing and lensing of the X-ray binaries. |
