GW190521 and Multi-Band, Multi-Messenger Astronomy

The new gravitational-wave signal GW190521 in LIGO and Virgo marks the first observational detection of the elusive intermediate-mass black holes. In this talk, I would review the implications of this historic discovery to cosmology and pair-instability supernovae theory. Further, I would highlight how this discovery opens a unique science case for a joint multi-band, multi-messenger gravitational-wave astronomy with the upcoming ESA/NASA space mission LISA and a potential gravitational wave experiment on the Moon.