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Fundamental Interactions Seminars
Seminar organized by the four teams of the group Fundamental Interactions.
Person in charge: Federico Piazza
Dedicated Day: Friday, 14:00
Place: CPT, Amphitheater on the 5th floor
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Next Fundamental Interactions Seminars
Friday 13 March
Intrinsic conformal geometry of nullinfinity and its gravitational wave
Yannick Herfray, Université Libre de Bruxelles
Our best current model for describing gravitational waves, as for example measured in LIGO, is a family of solution to vacuum Einstein equations called asymptoticallyflat spacetimes. Observers are then taken to be situated "at nullinfinity" and, since the seminal work of Bondi’s group and Sachs, gravitational waves are related to the presence of a certain tensor, the "asymptotic shear", appearing in an asymptotic expansion away from nullinfinity. Intuitively the presence of gravitational waves should correspond to the presence of some extra geometrical data at nullinfinity but such a geometrisation however proved to be quite elusive. This is essentially because the geometry of nullinfinity is of conformal nature which is notoriously tedious to work with. I will review these wellknown facts and show how modern methods in conformal geometry (namely tractor calculus) can be adapted to the degenerate conformal geometry of nullinfinity to encode the presence of gravitational waves in a completely geometrical way: the "asymptotic shear" is proved to be in 11 correspondence with choices of tractor connection, gravitational radiation is invariantly described by the tractor curvature and "softmodes" of the vacuum correspond to the degeneracy of flat tractor connections.
Seminars to come

Friday 20 March, 14h00 – 15h00
Séminaire Interactions fondamentales
Antoine Tilloy (Max Planck Institute of Quantum Optics, Munich) 