Today we have quite stringent constraints on possible violations of the weak-equivalence
principle from the comparison of the acceleration of test-bodies of different composition in
Earth's gravitational field. In the present paper, we propose a test of the weak-equivalence
principle in the strong gravitational field of black holes. We construct a relativistic reflection
model in which either the massive particles of the gas of the accretion disk or the photons
emitted by the disk may not follow the geodesics of the spacetime. We employ our model to …

Today we have quite stringent constraints on possible violations of the Weak Equivalence
Principle from the comparison of the acceleration of test-bodies of different composition in
Earth's gravitational field. In this talk, I show how we can test the Weak Equivalence Principle
in the strong gravitational field of black holes by studying the reflection features of their
accretion disks. Constraints on a possible violation of the Weak Equivalence Principle by
massive particles and X-ray photons are inferred from a NuSTAR observation of the black …