MICROSCOPE is a CNES-ESA-DLR-ONERA-CNRS-OCA-ZARM space mission that aimed to test the Weak Equivalence Principle (WEP) at the $10^{-15}$ level, i.e. two orders of magnitude better than the best "pre-MICROSCOPE" on-ground tests. The WEP is the cornerstone of General Relativity, the postulate that led Einstein to establish his theory: it states that all bodies fall at the same rate,...
Black holes comprise a remarkably elegant set of solutions of the Einstein field equations. Aside from their rich mathematical structure, they are nowadays accepted as legitimate astrophysical objects and are routinely used in order to explain astrophysical observations. Nonetheless, General Relativity black holes were for a long time regarded with skepticism by many, even Einstein himself, as...
General Relativity tells us that that a spinning source of gravity produces, in weak field approximation, both an attractive Newton-like force and a gravito-magnetic interaction. This is of course true for the whole Milky Way and in particular for its dark halo, if it exists. Here I discuss the opportunity of putting upper limits to the intensity of a possible galactic gravito-magnetic field,...
To date, the most precise tests of General Relativity have been achieved
through pulsar timing, albeit in the weak-field regime. Since pulsars are
some of the most precise and stable "clocks" in the Universe, present
observational efforts are focused on detecting pulsars in the vicinity of
supermassive black holes (most notably in the Galactic Centre), enabling
pulsar timing to be used as an...
The supermassive black hole in the center of our galaxy is the closest of its kind and the largest in the sky. It is surrounded by a small cluster of high velocity stars called S-stars. Their trajectories are governed by the gravitational field of the black hole. We used the Very Large Telescope (VLT) instruments GRAVITY and SINFONI to follow the star S2/S-02 during its pericenter passage,...
Abstract: I will present a simple and generic class of scalar-tensor theories that successfully realize dynamical damping of the effective cosmological constant, therefore providing a viable dynamical resolution of the fine-tuning cosmological constant problem. In contrast to early versions of this approach, the models considered do not suffer from unacceptable variations of Newton's constant,...
