Besides theoretical considerations of naturalness, the strongest evidence that our understanding of the laws of nature is incomplete is arguably provided by astrophysical observations. For instance, making sense of the dark sector that dominates the energy density of the universe is a key driver for physics beyond the Standard Model. Focusing on a well-motivated dark matter candidate, the QCD axion, I will discuss how different astrophysical observations, ranging from gravitational to electromagnetic waves, enable us to constrain its properties. Finally, I will describe several examples of the converse situation where physics BSM might account for astrophysical phenomena of uncertain origin
Roberto Capuzzo Dolcetta