Speaker
Description
Does dark matter experience gravity in the same way as ordinary matter? By throwing different objects from the Pisa tower, Galileo showed that they were all subject to the same acceleration, hence providing a demonstration of the so-called weak equivalence principle. However, the validity of this principle for dark matter remains a key open question, which is rarely addressed in cosmological analyses. In my talk, I will present two complementary approaches to answer this question in galaxy surveys. The first one relies on gravitational redshift, a consequence of the distortion of time in a gravitational potential, while the second one is based on a two-fluid description of ordinary and dark matter. I will show that these methods provide crucial information to constrain deviations from the equivalence principle and to distinguish between gravity modifications and non-standard dark matter scenarios. Hence, repeating Galileo’s experiment across the Universe might literally be a matter of time and two fluids.