Bound on induced gravitational wave background from primordial black holes

The today’s energy density of the induced (second order) gravitational wave background in the frequency region ∼10 −3 –10 3 Hz is constrained using the existing limits on primordial black hole production in the early Universe. It is shown, in particular, that at frequencies near ∼40 Hz (which is the region explored by LIGO detector), the value of the induced part of Ω GW cannot exceed (1−3) × 10 −7 . The spread of values of the bound is caused by the uncertainty in parameters of the gravitational collapse of black holes.