- For the public
- Teachers and pupils
After LIGO detected gravitational wave events produced by mergers of binary black holes (BHs) in 2015, researchers have aggressively studied the origin of the BHs with masses of the order of O(10) M_solar. In additional to astrophysical origins such as evolution of Pop.II and/or Pop.III stars, one of the attractive candidates of those BHs would be Primordial Black Holes (PBHs) which were produced in the early radiation dominated Universe due to the spherical collapse of regions which have a large density perturbation at the horizon scale at that time. I will review the current status of constraints on PBHs with introducing my own bounds on PBHs in terms of gamma-rays (arXiv:1604.05349 [astro-ph.CO]), CMB (arXiv:1707.04206 [astro-ph.CO]), BBN (arXiv:0912.5297 [astro-ph.CO]), and Higgs phenomenology (arXiv:1708.02138 [hep-ph]). I also introduce theoretical models to produce them including my works based on the inflationary Universe. I will also discuss our completely new production mechanisms in the early matter dominated Universe which had not been considered (arXiv:1707.03595 [gr-qc]).