What are the basic building blocks of Nature? What forces hold them together? These questions are at the heart of elementary particle physics. Theoretical physicists study and explore how to describe elementary particles and their interactions. There are several concrete hints that tell us that we currently know only part of the puzzle.

In order to explore what pieces are missing, and to get hints for completing the picture, it is paramount to get clues from experimental observations. The scientific approach is to compare experimental data to theoretical predictions. Obtaining the latter requires understanding of quantum field theory, which underpins the model for the known elementary particles and their interactions.

The Amplitudes research field focuses on understanding and computing probabilities of scattering processes in quantum field theory. The later are the essential building blocks for cross-sections that can be measured at particle colliders, such as the LHC at CERN, Geneva.

Apart from their phenomenological interest, scattering amplitudes also have intriguing mathematical properties. They satisfy a number of physical conditions, and have obvious and hidden symmetries. In some situations, the amplitudes can be uniquely determined from their symmetry and analytic properties. Many modern methods of computing them are based on such structural insights.

## Key words for specific research directions of the group:

- Scattering amplitudes of elementary particles
- Feynman integrals, differential equations, and special functions
- Infrared divergences in quantum field theory
- Conformal symmetry and supersymmetry
- AdS/CFT correspondence, N=4 super Yang-Mills