Exploring fundamental physics with tests of the equivalence principle from the lab to the Galactic Center

Aurélien Hees (SYRTE)

The Einstein equivalence principle is at the heart of the theory of General Relativity. This principle is not based on theoretical considerations but rather on experimental facts and is violated in numerous unification scenarios, Dark Matter models and Dark Energy models. In this presentation, I will review the motivations to test the equivalence principle and present recent experimental results that search for a breaking of the equivalence principle. I will briefly remind the current best « standard » tests of the equivalence principle. Then, I will focus on a model of Ultralight Dark Matter which breaks the equivalence principle and produces various signatures that can be searched for using atomic sensors. I will present several recent experimental results on this model. Finally, I will discuss two recent tests of the equivalence principle using measurements of short-period stars orbiting the supermassive black hole in our Galactic Center. The first one is related to the measurement of the gravitational redshift of the star S0-2/S2. The second one consists in a search for a variation of the fine structure constant around our Galactic Center.

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