My research focuses on the fundamental understanding of complex phenomena in nuclei. Complexity denotes here the emergence of significant differences in observables of systems which differ from one another in the presence of a single additional nucleon. The absence of any stable five-nucleon isotope in contrast to the exceptionally stable helium-4 core is one example. Most phenomena of this type have not yet been predicted from a fundamental theory. Neither has quantum chromodynamics (QCD) successfully described the two-nucleon bound state in terms of quarks and gluons, nor were the most accurate models for the interaction between two and three nucleons able to yield reliable predictions for exotic, extremely neutron rich nuclei. This ignorance hampers the search for both new elements at and beyond the drip line of nuclear stability, and new interaction mechanisms which are not part of the Standard Model of Particle Physics (SM).

My work combines the framework of effective field theories (EFT), which provides a consistent description of a system at different scales -- in a different context, it ensures that the dynamics of rain clouds can be simulated with the same accuracy independently of whether one models the cloud as a single, pliable object or as a composite of single drops -- with modern numerical techniques.

Thereby, I develop a link between nuclear properties, including reactions, and the fundamental laws of QCD, its parameters and symmetries; I address the general problem, as it pertains to particle, nuclear, and atomic physics as well as numerous other scientific disciplines, of predicting macroscopic complexity from microscopic degrees of freedom; I analyze to what extent two, three, and many are different.

Besides pushing our knowledge of the transition from few to many-body systems thus to the most advanced level yet, my work relates directly to current experimental efforts. Details on its relevance for and overlap with these ongoing and future physical experiments are given below under two categories:

first, the understanding of nuclei as they emerge from few-nucleon interactions, and second, the derivation of the few-nucleon interaction from QCD.