LISA sensitivity below 0.1 mHz

It has been clear for some time that the LISA mission can provide valuable new information concerning galaxy formation and evolution. If galaxies or pre-galactic structures contain massive black holes before their mergers, then these black holes may sink towards the centre of the newly formed structure and form a binary. The conditions under which the black holes will form a close binary that radiates gravitational waves strongly in less than a Hubble time have been discussed in a number of articles. Here, the gravitational wave sensitivity that LISA can achieve in order to look for such signals at frequencies below 0.1 mHz is discussed, and a specific sensitivity goal at frequencies down to 3 μHz is suggested.