Description
Important and challenging questions remain unanswered about the fundamental constituents of Nature, their interactions, and the evolution of the Universe and its extreme environments. Astroparticle physics, lying at the interface between particle physics, astrophysics and cosmology, aims to provide vital clues to answer them. A vibrant effort in theoretical astroparticle physics is needed to support, fully exploit and guide the ambitious experimental and observational programme in Europe and worldwide. We stress the importance of a balanced programme of theoretical, experimental and observational activities, in synergy with and complementary to the collider programme at CERN, to answer these challenging questions, exploring a broad range of physics scales and phenomena. - This contribution has been prepared by the EuCAPT Strategy Task Force, based on the input from the European astroparticle theory community and with the endorsement by 430 astroparticle theorists.
