Ricerc@Sapienza

Recently, decades of theoretical and experimental work on gravitational waves (GWs) physics have finally paid off in the historical detections of signals emitted by comparable mass binaries of black holes (BH) and neutron stars (NS) made by the LIGO/Virgo collaboration. This has opened up the possibility of GW astronomy, which will certainly continue to grow and open new paths to explore fundamental physics in the following decades.

To expand this even further, new GW observatories are already planned for the future, namely the space-based observatory LISA, which will allow us to explore different sources than the LIGO/Virgo detectors, such as supermassive black holes in extreme-mass ratio inspirals (EMRI). These will give us new insights both into the nature of these objects that are commonly found in the center of galaxies and into the very foundations of General Relativity (GR) and its possible modifications.

However, for this to come to be we must pave the way for this new experiment, much as it was done before the LIGO detections. EMRIs are remarkably different systems from the comparable mass binaries routinely observed by LIGO/Virgo detectors. Building tailor-made GW waveform models is therefore essential to search for new physics with EMRIs. With this project, we propose to investigate the nature of BHs and other extremely compact objects in the context of EMRIs by studying their gravitational deformations that can be found encoded in their quadrupole, which summarizes the details of its internal structure. Quadrupolar effects may leave a footprint in the GW emitted during the inspiral, which can be measured by LISA with exquisite precision, providing invaluable information on the physics of the binary. These must be considered when building the aforementioned models, so, ultimately, our project aims at giving a contribution to the modelling of EMRIs, which is part of the research lines of several international groups.