(plenary invited speaker)

Dark Matter with gravitational waves and microlensing

The path of gravitational waves can be modified by structures along the line of sight, that can refocus different paths into detectors on Earth. These gravitational lenses can result in large magnification factors for the gravitational waves. Since the maximum magnification of a source is inversely proportional to the size of the source, and the bulk of the gravitational waves are emitted in very small volumes (spheres with radii of 100 km or less for stellar black hole mergers), the magnifications factors of gravitational waves can exceed thousands when the gravitational lens in a massive galaxy, galaxy group of galaxy cluster. In this scenario, microlensing by stellar objects in the gravitational lens becomes inevitable. These microlenses can result in interference of the gravitational wave at the detector. In addition to stellar objects in the lens, candidates to dark matter, such as primordial black holes, could also result in microlensing (interference) effects. In this talk I discuss the lensing and microlensing of gravitational waves and the potential of lensed gravitational waves to constrain the abundance of primordial black holes with masses in the range few to tens of Msun.