Theory Colloquium

# Impossible Theories of Gravity

## by Brando Bellazzini (Institut de Physique Theorique, CEA/Saclay)

Wednesday, January 8, 2020 from to (Europe/Berlin)
at DESY Hamburg ( build. 2a, SR2 )
 Description Not every effective theory of fields and gravitational interactions at low energy can be embedded into a consistent theory of gravity at short distances. I will discuss how fundamental properties of scattering amplitudes, such as unitarity and causality of the underlying fundamental theory, can be used to spot inconsistent theories of gravity at low-energy, and hence throw them in the so-called swampland'’. I will focus on two general applications: the weak gravity conjecture for the physics of extremal black holes; and modified gravity theories of interest for late-time cosmology.