Macarena Lagos Gravitational Wave Cosmology Seminar

Gravitational waves (GWs) are novel signals that were detected for the first time in 2015, which led to the Nobel Prize in Physics two years later. To date, there have been 90 GW events confirmed and, in the coming years, we could be detecting 100 to 1000 GW events per year. These waves directly probe the behavior of gravity, and hence are ideal observables for answering open questions in cosmology. In particular, as these waves propagate towards us over cosmological distance, they are sensitive to the expansion of the Universe and the presence of crucial---yet unknown---constituents in the Universe, namely dark energy and dark matter. In this talk, I will first show how we can constrain the expansion of the Universe with GWs, and mention some signatures of dark energy. After that, I will show that, similarly to light, GWs can be gravitationally lensed by intervening galaxies and their dark matter halos. One important difference with light is that GW detections are sensitive to the phase of the wave, which can change due to gravitational lensing. I will show how this phase shift affects observations, and how it can be used as a unique signature to help identify future GW lensed events.