Virgo (en)
Virgo is a laser interferometer designed to detect gravitational waves. Virgo is operated and improved in Cascina, a small town near Pisa on the site of the European Gravitational Observatory (EGO), by an international collaboration of about 300 scientists from France, Italy, the Netherlands, Hungary, Poland, Spain, and Belgium (since July 2018).
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Projects
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We know that a lot of matter we cannot see affects the motion of the stars around the center of the galaxy. This matter is present on earth, and in theory can interact directly with the mirrors in LIGO-Virgo in a specific way depending on the mass of the constituent particles. Since the dark matter is always present, the signal is at a fixed frequency that impinges on the detector. We are developing methods that search for this unique signature of dark matter.
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The stochastic gravitational wave background (SGWB) originates from the superposition of gravitational waves of many astrophysical and cosmological sources. The variety of possible sources is huge, ranging from binary coalescences to cosmic strings or even gravitational waves produced during inflation or phase transitions. A detection of the SGWB would have a large impact on our understanding of black hole populations or cosmological models. Observing gravitational waves of inflation would be at least as revolutionary as the first observation of the cosmic microwave background. CP3 members are responsible for one of the three official directional searches conducted by LIGO and Virgo.
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The detection of gravitational waves from the merger of heavy binary black hole and neutron star systems has driven the worldwide interest in gravitational wave physics. However, we have only seen the last second or less of these systems’ lives. If the black holes were less massive, we could actually have seen them as they were slowly moving towards each other. Lighter black holes imply different physics and formation mechanisms for them in the universe, hence a detection of these so-called primordial black holes would be a major breakthrough in physics.
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If ultralight dark matter exists and is composed of bosons, dark matter clouds can form around black holes after their birth and grow exponentially in size by extracting energy and spin from the black holes. Once the cloud has fully formed, the bosons will couple to each other and annihilate, emitting almost monochromatic (fixed energy) gravitational waves for extremely long periods of time. The boson can be treated as a scalar, vector or tensor field, which all imply different timescales for growth and deletion, and gravitational wave signal strength. Additionally, the implications of a detection of differ for each of these fields.
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A gravitational wave detector consists of many coupled optical cavities, the shortest being centimeter scale with sub-millimeter beams and the longest being several kilometers long with several centimeter size beams. When an input beam’s shape is not matched to the cavity eigenmode (the preferred beam shape of the cavity), we speak of mode mismatch (MM). MM is a source of optical loss from the fundamental mode, shown in the top figure, into cylindrical higher order modes (HOMs) of which an example is shown in the bottom figure. Minimising optical losses in a gravitational wave detector is important if techniques such as squeezed light injection are to be more fruitful. At the moment, no gravitational wave detector has an automated way to control MM. We investigate error signal generation by detection of the cylindrical HOMs. These signals then serve as input for control of MM a coupled cavity set-up.