Ponente
Descripción
In 10 years since the first direct observation of a gravitational wave (GW), GW astronomy has made giant leaps, going from detecting loud binary black hole (BBH) coalescences, to binary neutron star (BNS) and black hole -- neutron star (BHNS) binary events, all the way to large-volume population analyses. Yet the vast majority of events are too faint to be directly detected with coherent matched filter searches, and moreover there are a slew of potential GW sources that have yet to be identified. The collection of all GWs that may not be directly resolved by our detectors build up incoherently, giving rise to a cumulative gravitational-wave background (GWB) signal. Given its incoherent and indeterminate nature, the GWB is described as a mean-0 stochastic field. Distinct GW sources imprint different signatures in the background spectrum, hence stochastic analyses are tailored to search for specific hallmarks such as frequency dependence or directional dependence to perform component separation and give optimal results.
In this talk, we describe the sources and signals contributing to the GWB, contextualising them within the fields of astrophysics, cosmology, and high energy physics. We then introduce the stochastic GW analysis methods routinely employed in the Laser Interferometer Gravitational-wave Observatory (LIGO), Virgo, and Kagra (LVK) collaboration searches for GWBs, and present recent search results using data from the first four observing runs, up to the first portion of observing run O4. These include upper limits on a number of different target signals including compact binary backgrounds, potential GWs from nearby radio sources, first-order phase transitions and cosmic string networks in the early Universe, and primordial black holes. We conclude by providing an outlook of the potential detections to come with future upgrades to the detector network.
