Dark Matter Gravity Waves at LIGO and LISA

We study the merger rate of dark matter PIMBHs(=Primordial Intermediate Mass Black Holes). We conclude that the black holes observed by LIGO in GW150914 and later events were probably not dark matter PIMBHs but rather the result of gravitational collapse of very massive stars. To study the PIMBHs by gravitational radiation will require a detector sensitive to frequencies below 10Hz and otherwise more sensitive than LIGO. The LISA detector, expected to come online in 2034, will be useful at frequencies below 1Hz but a second space-based detector beyond LISA, sensitive up to 10Hz, will be necessary fully to study dark matter.