Gravity, according to Einstein's general theory of relativity, is not a force acting between objects and transmitted through space; gravity is instead the result of the space-time curvature caused by the presence of mass or energy. If a massive object, such as a black hole (BH), would change its position in space due to an acceleration, as in the case of two BHs orbiting each other in a binary system, it would create continuous changes to the curvature of the space-time; these changes propagate at the speed of light and are what we call gravitational waves (GWs). When a GW passes through a GW detector, typically a laser interferometer, it will stretch and contract its arms, and as a consequence, the (laser) light travelling along its arms will create an interference pattern, which in turn produces a detectable signal. By studying this signal, one can infer the properties of the system that has generated the GW.
The current second generation of grvitational wave detectros
The main gravitational wave detectors that are currently involved in the observation of the Universe through this new observation window are the two LIGO interferometers, located in the US in Livingstone and Hanford, the Advanced Virgo interferometer, located in Italy, in Cascina, and the KAGRA interferometer, located in Japan in the Kamioka mountain; together they form the advanced LVK GW detector network. During the first three observing runs of the LVK detectors network some 93 gravitational wave events, mostly due to black hole coalescence events were detected and have already helped in better understanding the Universe.
The Einstein Telescope, a third-generation gravitatioanl wave detector
The Einstein Telescope (ET) is a third-generation GW detector under planning in Europe aimed to extend gravitational waves to searches to the early universe around 2035. The final configuration and location of this advanced gravitational wave observatory are currently under study and will be decided in 2025. There are two main candidate sites. One site candidate is in Italy, in the SOS Enattos mines in Sardegna; the other candidate site is in the EU Regio Rhine-Meusse site near the NL-B-D border. Also, the final detector configuration is under evaluation with a so-called xylophone triangular shape, with 10 km arm lengths, located in one of the two candidate regions or two identical L-shaped detectors located in both candidate locations, with arm lengths of 15 km each. In all cases the detector will operate underground, 100 m below the surface and at very low temperatures to reduce noice. ET is set to bring a breakthrough in our understanding of the Universe thanks to a much-improved sensitivity to gravitational waves in a sensitive region that extends to a few thousand Hz.
Group Activities
The group has an interest in the understanding of intermediate-mass black holes (IMBHs), in their possible role in the formation of supermassive black holes (SMBHs), and in fundamental physics problem that might relate to them. Dark matter for example might influence the waveform produced in the coalescence of IMBHs. In addition to the purely scientific aspect of this topic, we are also interested in the development of new analysis methodologies, especially those that benefit by the use of machine learning and that can possibly integrated at the interface between hardware and software such as FPGAs.
Contacts: Gianluca Inguglia