High Energy Physics

Long-range forces that couple selectively to particular forms of matter are one of the most historically significant scenarios for physics beyond the Standard Model. They can be studied, depending on the coupling and the range of the interaction, with many different probes, from tabletop experiments to cosmological observations. In this lecture, we discuss some of the experimental methods to detect them, such as equivalence-principle violation tests. We also discuss the impact of collective effects, which are peculiar to long-range-force scenarios, in concrete models. As one example, we touch on long-range forces coupling to dark matter and their role in cosmology.