ARC project GWAS

Gravitational Wave Science (GWAS)        

Gravitational waves (GW) are ripples of space-time that can be created by mass movements that satisfy certain conditions. Their effect on an object encountered along their path is a compression in one direction and a stretch in the perpendicular one. Because gravity is the weakest of the four fundamental forces, even some of the most energetic systems in the universe produce GWs whose observable effects on Earth are exceedingly small. The current GW detectors are L-shaped laser interferometers capable of measuring variations in the lengths of their km-long arms of the order of 10-18 meters via changes in the interference pattern produced by their laser beams. Such detectors demand cutting-edge technologies in the fields of optics, mechanics, electronics, materials science, ultra-high vacuum, and data science in order to guarantee the required discrimination of the tiny GW signals from noise of various nature that can arise in all interferometer components or from the surrounding environment.

The two LIGO interferometers in the USA and the Virgo interferometer at the European Gravitational Observatory (EGO) in Cascina, near Pisa (Italy) are the three most sensitive GW detectors in operation to date. The Virgo Collaboration counts about 280 members and 26 European research institutions. The two LIGO detectors came into operation after a long phase of significant upgrades in September 2015 for the so called observation run O1, in which the first observation of GWs was made. The Virgo detector joined LIGO toward the end of the observing run O2 in August 2017. LIGO and Virgo have a memorandum of agreement according to which data from the three interferometers is shared, data analyses are performed jointly, and publications are signed jointly.

The LIGO and Virgo Collaborations are currently in their third observation run O3, which will extend from the start of 2019 until mid of 2020. At the same time as observing run O3, the LIGO and Virgo Collaboration will start activities for a major upgrade of the detectors. This first upgrades are expected to be put in operation at the beginning of 2021 when the run O4 run will begin. In the year 2022 installation of the phase-2 upgraded systems will begin and is expected to be completed by the end of 2023, when new observation runs will be performed. The observation runs will extend until 2028 at least as part of the strategy that will lead to the so-called 3rd generation GW detectors: Einstein Telescope1 (ET) in Europe and Cosmic Explorer in the US. The third-generation detectors are currently expected to be online around the year 2032. In this context applications for funds to build a prototype, called ET pathfinder, in the area around Maastricht, Aachen and Liège, have been introduced in the framework of the Interreg programmes Vlaanderen – Nederland2 and Euregio Meuse-Rhine3 of the European Union. The former application has just been approved and has obtained a budget of 14 M€. The interconnection between the ET endeavour, LIGO and Virgo is very tight both at the level of the scientific communities (very large overlap between the ET and Virgo Collaborations) and at the level of the scientific activities (as mentioned previously LIGO and Virgo perform physics data analyses together sharing data, tools and personpower).

Promoters of the convention:
Giacomo BRUNO (UCLouvain, Promoteur Porte-Parole), Christophe COLLETTE (ULiège), Jean-René CUDELL (ULiège) et Christophe RINGEVAL (UCLouvain)

Individuals (present and past):
Pierre Auclair, Francesca Badaracco, Ricardo Cabrita, Disrael Da Cuhna, Federico De Lillo, Antoine Depasse, Elvis Ferreira, Jef Heynen, Cristian Joana, Andrew Miller, Magdalena Sieniawska, Andres Tanasijczuk, Joris Van Heijningen, Stavros Venikoudis, Morgane Zeoli.

Theses defended as part of this project:

• Cristian Joana, Cosmic inhomogeneities in the early universe: a numerical relativity approach, 21/10/2022, superviseurs Christophe Ringeval and Sebastien Clesse (ULB).
• Federico De Lillo, Searching for Stochastic Gravitational-Wave Backgrounds with LIGO and Virgo Detectors, 27/05/2024, superviseur Giacomo Bruno (UCLOuvain).